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Author Topic: The Fossil Record: Evolution or  (Read 349 times)
The Hunter of Souls
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« on: September 14, 2005, 03:42:41 PM »

Having personally worked in the University of IL in Chicago as a real Paleontologist
I just wanted to make clear why I beleve in both God. and how evolution
was just a tool he/she/it used to create life as we know it.
The following is a paper I wrote on the subject a couple of years ago.

Creationism can be defined as the belief that a literal interpretation of one's preferred religious scripture is more in line with the empirical observations of science than the Darwinian paradigm (and any similar paradigms, e.g. Punctuated Equilibrium, Lamarckism, etc)

The Creationist-Evolutionist controversy represents a clash of paradigms, of two ways of relating to the world. This clash is like a mighty battle between the two pillars of our Western society - the scientific rationalistic approach (stemming ultimately from the Greeks, men like Thales and Aristotle, and reinterpreted through Galileo, Newton, and others of their caliber) and the Judeo-Christian theistic but also in its own way rationalistic approach, deriving from post-medieval religiosity, especially the Protestant revolution with its reliance on strict biblical literalism.

It is precisely because Creationism comes from the same Protestant milieu as Science, Creationists try to take a scientific slant on things.  In fact, they claim that they are actually the one's who are scientific and rational, and it is the evolutionists who are the irrational, religious dogmatic ones!  Strange claim indeed!  Is there is any truth in it?  Well, I am not here to persuade anyone, but if you want to decide for yourself you can check out some of the links assembled below(and the links from those links).

One reason Creationism is so widespread in America (much less so elsewhere in the Western World!) is not education or lack of it (as many scientist naively believe), but simply a cultural upbringing. America was founded by puritans, and hence the stern protestant element is very strong. In England or Australia Creationists are simply an eccentric minority, with no political clout.

Time is a particular stumbling block for Creationists.  Most people cannot envisage anything beyond a few thousand years - in fact even anything back beyond a few centuries is difficult!  Hence it is much easier for these people to take comfort in certainties like religious dogma (it is also easy, mind you, for evolutionists to take comfort in certainties like scientific dogma ;-)

Charles Darwin suggested the mechanism for evolution was through natural selection, which involves the following premises:

Individuals that make up a population are not all identical (variability)
this variation can be inherited (Heritable Variation in the population)
Organisms have the potential to increase in numbers greatly in excess of the ability of their    environment to support them (limits on reproductive success)
Variation leads to differential rates in survival and reproductive success among the variations. Therefore those individuals with inheritable traits that increase their chances of successful reproduction will leave more offspring.  (natural selection)
Differential survival and reproduction leads to a shift in the frequency of characters.  If this process goes on long enough, parent and daughter species can no longer interbreed, and there results a new species.
Therefore the environment "selects" (through random chance) which individuals successfully leave offspring for the next generation.  ("Survival of the Fittest")  Even very small variations that provide even very small advantages in reproductive success will be favored, while small variations that decrease reproductive success will be eliminated.  Over thousands of generations these changes can produce even very large changes; such as the biological diversity of different organisms.

THE MODERN SYNTHESIS
A Theory of the Mechanism of Evolution
(version 1.5, January 22, 1993)

Many people do not understand current ideas about evolution. The following is a brief summary of the modern consensus among evolutionary biologists.

The idea that life on Earth has evolved was widely discussed in Europe in the late 1700's and the early part of the last century. In 1859 Charles Darwin supplied a mechanism, namely natural selection, that could explain how evolution occurs. Darwin's theory of natural selection helped to convince most people that life has evolved and this point has not been seriously challenged in the past one hundred and thirty years.

It is important to note that Darwin's book "The Origin of Species by Means of Natural Selection" did two things. It summarized all of the evidence in favor of the idea that all organisms have descended with modification from a common ancestor, and thus built a strong case for evolution. In addition Darwin advocated natural selection as a mechanism of evolution. Biologists no longer question whether evolution has occurred or is occurring. That part of Darwin's book is now considered to be so overwhelmingly demonstrated that is often referred to as the FACT of evolution. However, the MECHANISM of evolution is still debated.

We have learned much since Darwin's time and it is no longer appropriate to claim that evolutionary biologists believe that Darwin's theory of Natural Selection is the best theory of the mechanism of evolution. I can understand why this point may not be appreciated by the average non-scientist because natural selection is easy to understand at a superficial level. It has been widely promoted in the popular press and the image of "survival of the fittest" is too powerful and too convenient.

During the first part of this century the incorporation of genetics and population biology into studies of evolution led to a Neo-Darwinian theory of evolution that recognized the importance of mutation and variation within a population. Natural selection then became a process that altered the frequency of genes in a population and this defined evolution. This point of view held sway for many decades but more recently the classic Neo-Darwinian view has been replaced by a new concept which includes several other mechanisms in addition to natural selection. Current ideas on evolution are usually referred to as the Modern Synthesis which is described by Futuyma;

"The major tenets of the evolutionary synthesis, then, were that populations contain genetic variation that arises by random (i.e.. not adaptively directed) mutation and recombination; that populations evolve by changes in gene frequency brought about by random genetic drift, gene flow, and especially natural selection; that most adaptive genetic variants have individually slight phenotypic effects so that phenotypic changes are gradual (although some alleles with discrete effects may be advantageous, as in certain color polymorphisms); that diversification comes about by speciation, which normally entails the gradual evolution of reproductive isolation among populations; and that these processes, continued for sufficiently long, give rise to changes of such great magnitude as to warrant the designation of higher taxonomic levels (genera, families, and so forth)."

Futuyma, D.J. in EVOLUTIONARY BIOLOGY, Sinauer Associates, 1986; p.12
This description would be incomprehensible to Darwin since he was unaware of genes and genetic drift. The modern theory of the mechanism of evolution differs from Darwinism in three important respects:

It recognizes several mechanisms of evolution in addition to natural selection. One of these, random genetic drift, may be as important as natural selection.
It recognizes that characteristics are inherited as discrete entities called genes. Variation within a population is due to the presence of multiple alleles of a gene.
It postulates that speciation is (usually) due to the gradual accumulation of small genetic changes. This is equivalent to saying that macroevolution is simply a lot of microevolution.
In other words, the Modern Synthesis is a theory about how evolution works at the level of genes, phenotypes, and populations whereas Darwinism was concerned mainly with organisms, speciation and individuals. This is a major paradigm shift and those who fail to appreciate it find themselves out of step with the thinking of evolutionary biologists. Many instances of such confusion can be seen here in the newsgroups, in the popular press, and in the writings of anti-evolutionists.

The major controversy among evolutionists today concerns the validity of point #3 (above). The are many who believe that the fossil record at any one site does not show gradual change but instead long periods of stasis followed by rapid speciation. This model is referred to as Punctuated Equilibrium and it is widely accepted as true, at least in some cases. The debate is over the relative contributions of gradual versus punctuated change, the average size of the punctuations, and the mechanism. To a large extent the debate is over the use of terms and definitions, not over fundamentals. No new mechanisms of evolution are needed to explain the model.

Some scientists continue to refer to modern thought in evolution as Neo-Darwinian. In some cases these scientists do not understand that the field has changed but in other cases they are referring to what I have called the Modern Synthesis, only they have retained the old name.

The "Creationist" Religious explanation...

The "Creationist" (or Fundamentalist) Religious explanation draws from a literal reading of the Biblical book of Genesis, which was originally an old Hebraic creation myth, interpreted through the theology of the later (from about several centuries C.E..) Christian Church.  The timescale is claustrophobically short: Creation came about through the activity of a single supernatural entity, "God", who created the universe and all life in six 24 hour days about 6000 or 10,000 years ago.  Man did not descend from the apes, but was created  personally by God, and thus the only creature to  have a soul.  There is no evolution or transformation; the whole cosmos is static.

http://www.pathlights.com/ce_encyclopedia/
a huge amount of material here. This would seem to be the best (in the sense of most persuasive, if you are that way inclined) Creationist site around.

http://www.answersingenesis.org/home/area/magazines/technical.asp
includes some on-line essays and a and synopsis of published issues of the magazine CREATION ex nihilo.

http://www.sjchurchofchrist.org/philosci.shtml
an otherwise unusually intelligent and perceptive critique of scientific method and the current evolution paradigm (ignoring the common Creationist reliance on religious dogma weakens the argument).  I say otherwise because the central thesis of this fellow's argument revolves around the claim that the early atmosphere was non-reducing, i.e. oxygen-rich.  This assumption, which goes against the entire current body of body of knowledge regarding the evolution of the earth's atmosphere, the appearance of oxygen, etc, is based on one single quotation of a tentative "may have" half-way down this page, and other selective quotes regarding assumptions of amino acid synthesis.  In view of the powerful critique of the way science works on his previous page, this pathetic follow through is particularly disappointing.

http://www.evolutionisfalse.org/
I like this Creationist site because there are a lot of funny drawings of dinosaurs and other prehistoric animals.  The central theme here is that gaps in the fossil record and the absence of links between different groups speak against the reality of continual evolution.  Basically follows Dr. Duane T. Gish and Dr. Henry M. Morris, the two foremost creationists.  In fact the fossil record is not nearly as incomplete as the fellow who put this site together (and all creationists) indicate.

Pro-Christian pro-evolution:
The "Liberal" Religious Explanation.

The "Liberal" Religious Explanation is similar to the above, but sees Genesis as symbolic rather than literal.  Evolution (Science) is the means by which God  (Religion) acts behind the scenes to bring about the  creation of life.  Science and religion are complementary.  Man evolved from the apes, but his/her soul comes from God.  Religious references refer to symbolic rather than literal facts - e.g. liberal Christians and Jews say the six days are really six "ages" of indeterminate length.

http://www.prehistoricplanet.com/features/paleontologists/bakker.htm
the famous paleontologist (and a close personal friend mind you)who is also a Protestant preacher and argues passionately that theology and evolution are not incompatible.

What is a transitional fossil?
The term "transitional fossil" is used at least two different ways on talk.origins, often leading to muddled and stalemated arguments. I call these two meanings the "general lineage" and the "species-to-species transition":

"General lineage":
This is a sequence of similar genera or families, linking an older group to a very different younger group. Each step in the sequence consists of some fossils that represent a certain genus or family, and the whole sequence often covers a span of tens of millions of years. A lineage like this shows obvious morphological intermediates for every major structural change, and the fossils occur roughly (but often not exactly) in the expected order. Usually there are still gaps between each of the groups -- few or none of the speciation events are preserved. Sometimes the individual specimens are not thought to be directly ancestral to the next-youngest fossils (i.e., they may be "cousins" or "uncles" rather than "parents"). However, they are assumed to be closely related to the actual ancestor, since they have intermediate morphology compared to the next-oldest and next-youngest "links". The major point of these general lineages is that animals with intermediate morphology existed at the appropriate times, and thus that the transitions from the proposed ancestors are fully plausible. General lineages are known for almost all modern groups of vertebrates, and make up the bulk of this post.

"Species-to-species transition":
This is a set of numerous individual fossils that show a change between one species and another. It's a very fine-grained sequence documenting the actual speciation event, usually covering less than a million years. These species-to-species transitions are unmistakable when they are found. Throughout successive strata you see the population averages of teeth, feet, vertebrae, etc., changing from what is typical of the first species to what is typical of the next species. Sometimes, these sequences occur only in a limited geographic area (the place where the speciation actually occurred), with analyses from any other area showing an apparently "sudden" change. Other times, though, the transition can be seen over a very wide geological area. Many "species-to-species transitions" are known, mostly for marine invertebrates and recent mammals (both those groups tend to have good fossil records), though they are not as abundant as the general lineages (see below for why this is so). Part 2 lists numerous species-to-species transitions from the mammals.

Transitions to New Higher Taxa
As you'll see throughout this FAQ, both types of transitions often result in a new "higher taxon" (a new genus, family, order, etc.) from a species belonging to a different, older taxon. There is nothing magical about this. The first members of the new group are not bizarre, chimeric animals; they are simply a new, slightly different species, barely different from the parent species. Eventually they give rise to a more different species, which in turn gives rise to a still more different species, and so on, until the descendents are radically different from the original parent stock. For example, the Order Perissodactyla (horses, etc.) and the Order Cetacea (whales) can both be traced back to early Eocene animals that looked only marginally different from each other, and didn't look at all like horses or whales. (They looked rather like small, dumb foxes with raccoon-like feet and simple teeth.) But over the following tens of millions of years, the descendents of those animals became more and more different, and now we call them two different orders.

There are now several known cases of species-to-species transitions that resulted in the first members of new higher taxa. See part 2 for details.

Why do gaps exist? (or seem to exist)
Ideally, of course, we would like to know each lineage right down to the species level, and have detailed species-to-species transitions linking every species in the lineage. But in practice, we get an uneven mix of the two, with only a few species-to-species transitions, and occasionally long time breaks in the lineage. Many laypeople even have the (incorrect) impression that the situation is even worse, and that there are no known transitions at all. Why are there still gaps? And why do many people think that there are even more gaps than there really are?

Stratigraphic gaps
The first and most major reason for gaps is "stratigraphic discontinuities", meaning that fossil-bearing strata are not at all continuous. There are often large time breaks from one stratum to the next, and there are even some times for which no fossil strata have been found. For instance, the Aalenian (mid-Jurassic) has shown no known tetrapod fossils anywhere in the world, and other stratigraphic stages in the Carboniferous, Jurassic, and Cretaceous have produced only a few mangled tetrapods. Most other strata have produced at least one fossil from between 50% and 100% of the vertebrate families that we know had already arisen by then (Benton, 1989) -- so the vertebrate record at the family level is only about 75% complete, and much less complete at the genus or species level. (One study estimated that we may have fossils from as little as 3% of the species that existed in the Eocene!) This, obviously, is the major reason for a break in a general lineage. To further complicate the picture, certain types of animals tend not to get fossilized -- terrestrial animals, small animals, fragile animals, and forest-dwellers are worst. And finally, fossils from very early times just don't survive the passage of eons very well, what with all the folding, crushing, and melting that goes on. Due to these facts of life and death, there will always be some major breaks in the fossil record.

Species-to-species transitions are even harder to document. To demonstrate anything about how a species arose, whether it arose gradually or suddenly, you need exceptionally complete strata, with many dead animals buried under constant, rapid sedimentation. This is rare for terrestrial animals. Even the famous Clark's Fork (Wyoming) site, known for its fine Eocene mammal transitions, only has about one fossil per lineage about every 27,000 years. Luckily, this is enough to record most episodes of evolutionary change (provided that they occurred at Clark's Fork Basin and not somewhere else), though it misses the most rapid evolutionary bursts. In general, in order to document transitions between species, you specimens separated by only tens of thousands of years (e.g. every 20,000-80,000 years). If you have only one specimen for hundreds of thousands of years (e.g. every 500,000 years), you can usually determine the order of species, but not the transitions between species. If you have a specimen every million years, you can get the order of genera, but not which species were involved. And so on. These are rough estimates (from Gingerich, 1976, 1980) but should give an idea of the completeness required.

Note that fossils separated by more than about a hundred thousand years cannot show anything about how a species arose. Think about it: there could have been a smooth transition, or the species could have appeared suddenly, but either way, if there aren't enough fossils, we can't tell which way it happened.

Discovery of the fossils
The second reason for gaps is that most fossils undoubtedly have not been found. Only two continents, Europe and North America, have been adequately surveyed for fossil-bearing strata. As the other continents are slowly surveyed, many formerly mysterious gaps are being filled (e.g., the long-missing rodent/lagomorph ancestors were recently found in Asia). Of course, even in known strata, the fossils may not be uncovered unless a roadcut or quarry is built (this is how we got most of our North American Devonian fish fossils), and may not be collected unless some truly dedicated researcher spends a long, nasty chunk of time out in the sun, and an even longer time in the lab sorting and analyzing the fossils. Here's one description of the work involved in finding early mammal fossils: "To be a successful sorter demands a rare combination of attributes: acute observation allied with the anatomical knowledge to recognise the mammalian teeth, even if they are broken or abraded, has to be combined with the enthusiasm and intellectual drive to keep at the boring and soul-destroying task of examining tens of thousands of unwanted fish teeth to eventually pick out the rare mammalian tooth. On an average one mammalian tooth is found per 200 kg of bone-bed." (Kermack, 1984.)

Documenting a species-to-species transition is particularly grueling, as it requires collection and analysis of hundreds of specimens. Typically we must wait for some paleontologist to take it on the job of studying a certain taxon in a certain site in detail. Almost nobody did this sort of work before the mid-1970's, and even now only a small subset of researchers do it. For example, Phillip Gingerich was one of the first scientists to study species-species transitions, and it took him ten years to produce the first detailed studies of just two lineages (see part 2, primates and condylarths). In a (later) 1980 paper he said: "the detailed species level evolutionary patterns discussed here represent only six genera in an early Wasatchian fauna containing approximately 50 or more mammalian genera, most of which remain to be analyzed." [emphasis mine]

Getting the word out
There's a third, unexpected reason that transitions seem so little known. It's that even when they are found, they're not popularized. The only times a transitional fossil is noticed much is if it connects two noticably different groups (such as the "walking whale" fossil reported in 1993), or if illustrates something about the tempo and mode of evolution (such as Gingerich's work). Most transitional fossils are only mentioned in the primary literature, often buried in incredibly dense and tedious "skull & bones" papers utterly inaccessible to the general public. Later references to those papers usually collapse the known species-to-species sequences to the genus or family level. The two major college-level textbooks of vertebrate paleontology (Carroll 1988, and Colbert & Morales 1991) often don't even describe anything below the family level! And finally, many of the species-to-species transitions were described too recently to have made it into the books yet.

Why don't paleontologists bother to popularize the detailed lineages and species-to-species transitions? Because it is thought to be unnecessary detail. For instance, it takes an entire book to describe the horse fossils even partially (e.g. MacFadden's "Fossil Horses"), so most authors just collapse the horse sequence to a series of genera. Paleontologists clearly consider the occurrence of evolution to be a settled question, so obvious as to be beyond rational dispute, so, they think, why waste valuable textbook space on such tedious detail?

Misunderstanding of quotes about punctuated equilibrium
What paleontologists do get excited about are topics like the average rate of evolution. When exceptionally complete fossil sites are studied, usually a mix of patterns are seen: some species still seem to appear suddenly, while others clearly appear gradually. Once they arise, some species stay mostly the same, while others continue to change gradually. Paleontologists usually attribute these differences to a mix of slow evolution and rapid evolution (or "punctuated equilibrium": sudden bursts of evolution followed by stasis), in combination with the immigration of new species from the as-yet-undiscovered places where they first arose.

There's been a heated debate about which of these modes of evolution is most common, and this debate has been largely misquoted by laypeople, particularly creationists. Virtually all of the quotes of paleontologists saying things like "the gaps in the fossil record are real" are taken out of context from this ongoing debate about punctuated equilibrium. Actually, no paleontologist that I know of doubts that evolution has occurred, and most agree that at least sometimes it occurs gradually. The fossil evidence that contributed to that consensus is summarized in the rest of this FAQ. What they're arguing about is how often it occurs gradually. You can make up your own mind about that. (As a starting point, check out Gingerich, 1980, who found 24 gradual speciations and 14 sudden appearances in early Eocene mammals; MacFadden, 1985, who found 5 cases of gradual anagenesis, 5 cases of probable cladogenesis, and 6 sudden appearances in fossil horses; and the numerous papers in Chaline, 1983. Most studies that I've read find between 1/4-2/3 of the speciations occurring fairly gradually.)

Predictions of creationism and of evolution
Before launching into the transitional fossils, I'd like to run through the two of the major models of life's origins, biblical creationism and modern evolutionary theory, and see what they predict about the fossil record.

Most forms of creationism hold that all "kinds" were created separately, as described in Genesis. Unfortunately there is no biological definition of "kind"; it appears to be a vague term referring to our psychological perception of types of organisms such as "dog", "tree", or "ant". In previous centuries, creationists equated "kind" to species. With the discovery of more and more evidence for derivation of one species from another, creationists bumped "kind" further up to mean higher taxonomic levels, such as "genus", or "family", though this lumps a large variety of animals in the same "kind". Some creationists say that "kind" cannot be defined in biological terms.
Predictions of creationism: Creationists usually don't state the predictions of creationism, but I'll take a stab at it here. First, though there are several different sorts of creationism, all of them agree that there should be no transitional fossils at all between "kinds". For example, if "kind" means "species", creationism apparently predicts that there should be no species-to-species transitions whatsoever in the fossil record. If "kind" means "genus" or "family" or "order", there should be no species-to-species transitions that cross genus, family, or order lines. Furthermore, creationism apparently predicts that since life did not originate by descent from a common ancestor, fossils should not appear in a temporal progression, and it should not be possible to link modern taxa to much older, very different taxa through a "general lineage" of similar and progressively older fossils.

Other predictions vary with the model of creationism. For instance, an older model of creationism states that fossils were created during six metaphorical "days" that may each have taken millenia to pass. This form of creationism predicts that fossils should be found in the same order outlined in Genesis: seed-bearing trees first, then all aquatic animals and flying animals, then all terrestrial animals, then humans.

In contrast, many modern U.S. creationists believe the "Flood Theory" of the origin of fossils. The "Flood Theory" is derived from a strictly literal reading of the Bible, and states that all geological strata, and the fossils imbedded in them, were formed during the forty-day flood of Noah's time. Predictions of the Flood Theory apparently include the following:

most rock should be sedimentary and indicative of cataclysmic flooding. There should be no rock formations that indicate the passing of millenia of gradual accumulation of undisturbed sediment, such as multi-layered riverbed formations. There should be no large lava flows layered on top of each other, and definitely not with successively older radiometric dates in the lower levels.
terrestrial animal fossils should either not be sorted at all, or should be sorted by some "hydrodynamic" aspect such as body size, with, for instance, extinct elephants and large dinosaurs in the lowest layers, and small primitive dinosaurs in the upper layers. Terrestrial animal fossils should not be sorted by subtle anatomical details (such as, say, the number of cusps on the fourth premolar).
marine animals are a puzzle, since it is unclear that a Flood would cause any extinctions of aquatic animals. If such extinctions did occur, aquatic fossils would perhaps be "sorted" by body size or ecological niche (bottom-feeder vs. surface swimmer). For instance, plesiosaurs, primitive whales, and placoderm fishes (relatively slow-swimming and quite large) should end up in the same layers. Ichthyosaurs and porpoises (smaller, faster swimmers with almost identical body shapes and similar diets) should also occur in the same layers.
there should be no sorting of large rooted structures such as coral reefs and trees. There should likewise not be differential sorting of microscopic structures of the same size and shape, such as pollen grains.
sorting, if it occurs at all, should be quite imperfect. With only 40 days for sorting, there should be occasional examples of individual fossils that ended up in the "wrong" layer -- the occasional mammal and human fossil in Paleozoic rocks, for instance, and the occasional trilobite and plesiosaur in Cenozoic rocks.
sorting should not correlate with date of the surrounding rocks. If all fossils were created by Noah's flood, there is no conceivable reason that, for instance, lower layers of fossils should always end up sandwiched between lava rocks with old radiometric dates.
Finally, some creationists believe that fossils were created by miraculous processes not operating today. (Many of these creationists combine this idea with the Flood Theory, as follows: fossils were created during the Flood, but were "sorted" by a miraculous process not observable or understandable today.) Obviously, such a theory makes no testable predictions...except perhaps for the prediction that geological formations should not bear any obvious resemblance to processes occurring today.

Modern evolutionary theory holds that the living vertebrates arose from a common ancestor that lived hundreds of millions of years ago (via "descent with modification"; variety is introduced by mutation, genetic drift, and recombination, and is acted on by natural selection). Various proposed mechanisms of evolution differ in the expected rate and tempo of evolutionary change.
Predictions of evolutionary theory: Evolutionary theory predicts that fossils should appear in a temporal progression, in a nested hierarchy of lineages, and that it should be possible to link modern animals to older, very different animals. In addition, the "punctuated equilibrium" model also predicts that new species should often appear "suddenly" (within 500,000 years or less) and then experience long periods of stasis. Where the record is exceptionally good, we should find a few local, rapid transitions between species. The "phyletic gradualism" model predicts that most species should change gradually throughout time, and that where the record is good, there should be many slow, smooth species-to-species transitions. These two models are not mutually exclusive -- in fact they are often viewed as two extremes of a continuum -- and both agree that at least some species-to-species transitions should be found.


This post mostly consists of a partial list of known transitions from the vertebrate fossil record. The transitions in part 1 are mostly general lineages, while in part 2 there are both general lineages and species- to-species transitions. In a hopeless attempt to save space, I concentrated almost exclusively on groups that left living descendants, ignoring all the hundreds of other groups and side-branches that have died out. I also skipped entire groups of vertebrates (most notably the dinosaurs and modern fish) in order to emphasize mammals, the group talk.origins'ers are most interested in. Note that the general lineages sometimes include "cousin" fossils. These are fossils that are thought to be very similar and closely related to the actual ancestor, but for various reasons are suspected not to be that ancestor. I have labelled them clearly in the text. I've also pointed out some of the significant remaining gaps in the vertebrate fossil record.

I got most of the information from Colbert & Morales' Evolution of the Vertebrates (1991), Carroll's Vertebrate Paleontology and Evolution (198, Benton's The Phylogeny and Classification of the Tetrapods (198, and from various recent papers from the scientific literature. These sources are all listed in the reference section at the end of part 2.

The time of first known appearance of each fossil is given in parentheses after the fossil name, including absolute dates when I could find them. The only exceptions are a few cases where my source didn't mention a date and it wasn't listed in Carroll's text. All of these fossils were dated by *independent* means, typically by using several different methods of radiometric dating on the strata around the fossil, and/or by cross-correlating to dated strata at other sites (e.g. MacFadden et al., 1991). The information assumes that these dating methods are accurate. If you have questions about the many dating methods used by paleontologists, get yourself a good textbook of sedimentary geology. Paleontologists are generally sharp cookies, and are quite persnickety about using good dating techniques.

Some terminology
"Anagenesis", "phyletic evolution":
Evolution in which an older species, as a whole, changes into a new descendent species, such that the ancestor is transformed into the descendant.
"Cladogenesis":
Evolution in which a daughter species splits off from a population of the older species, after which both the old and the young species coexist together. Notice that this allows a descendant to coexist with its ancestor.
"Chronocline":
Gradual change in one lineage over time
Ma:
Millions of years ago (a date)
my:
Millions of years (a duration)
Timescale
CENOZOIC

(See part 2) 65-0 Ma Mammals & birds & teleost fish dominant

MESOZOIC

Cretaceous 144-65 Ma Dinosaurs dominant. Small mammals, birds.

Jurassic 213-144 Ma Dinosaurs dominant. First mammals, then first birds.

Triassic 248-213 Ma Mammalian reptiles dominant. First dinosaurs.

PALEOZOIC

Permian 286-248 Ma Amphibians dominant. First mammal-like reptiles.

Pennsylvanian 320-286 Ma Amphibians dominant. First reptiles.

Mississippian 360-320 Ma Big terrestrial amphibians, fishes.

Devonian 408-360 Ma Fish dominant. First amphibians.

Silurian 438-408 Ma First ray-finned & lobe-finned fish.

Ordovician 505-438 Ma More jawless fishes.

Cambrian 590-505 Ma First jawless fishes.


Summary of the known vertebrate fossil record
(We start off with primitive jawless fish.)

Transition from primitive jawless fish to sharks, skates, and rays
Late Silurian -- first little simple shark-like denticles.
Early Devonian -- first recognizable shark teeth, clearly derived from scales.
GAP: Note that these first, very very old traces of shark-like animals are so fragmentary that we can't get much detailed information. So, we don't know which jawless fish was the actual ancestor of early sharks.

Cladoselache (late Devonian) -- Magnificent early shark fossils, found in Cleveland roadcuts during the construction of the U.S. interstate highways. Probably not directly ancestral to sharks, but gives a remarkable picture of general early shark anatomy, down to the muscle fibers!
Tristychius & similar hybodonts (early Mississippian) -- Primitive proto-sharks with broad-based but otherwise shark-like fins.
Ctenacanthus & similar ctenacanthids (late Devonian) -- Primitive, slow sharks with broad-based shark-like fins & fin spines. Probably ancestral to all modern sharks, skates, and rays. Fragmentary fin spines (Triassic) -- from more advanced sharks.
Paleospinax (early Jurassic) -- More advanced features such as detached upper jaw, but retains primitive ctenacanthid features such as two dorsal spines, primitive teeth, etc.
Spathobatis (late Jurassic) -- First proto-ray.
Protospinax (late Jurassic) -- A very early shark/skate. After this, first heterodonts, hexanchids, & nurse sharks appear (late Jurassic). Other shark groups date from the Cretaceous or Eocene. First true skates known from Upper Cretaceous.
A separate lineage leads from the ctenacanthids through Echinochimaera (late Mississippian) and Similihari (late Pennsylvanian) to the modern ratfish.

Transition from from primitive jawless fish to bony fish
Upper Silurian -- first little scales found.
GAP: Once again, the first traces are so fragmentary that the actual ancestor can't be identified.

Acanthodians(?) (Silurian) -- A puzzling group of spiny fish with similarities to early bony fish.
Palaeoniscoids (e.g. Cheirolepis, Mimia; early Devonian) -- Primitive bony ray-finned fishes that gave rise to the vast majority of living fish. Heavy acanthodian-type scales, acanthodian-like skull, and big notochord.
Canobius, Aeduella (Carboniferous) -- Later paleoniscoids with smaller, more advanced jaws.
Parasemionotus (early Triassic) -- "Holostean" fish with modified cheeks but still many primitive features. Almost exactly intermediate between the late paleoniscoids & first teleosts. Note: most of these fish lived in seasonal rivers and had lungs. Repeat: lungs first evolved in fish.
Oreochima & similar pholidophorids (late Triassic) -- The most primitive teleosts, with lighter scales (almost cycloid), partially ossified vertebrae, more advanced cheeks & jaws.
Leptolepis & similar leptolepids (Jurassic) -- More advanced with fully ossified vertebrae & cycloid scales. The Jurassic leptolepids radiated into the modern teleosts (the massive, successful group of fishes that are almost totally dominant today). Lung transformed into swim bladder.
Eels & sardines date from the late Jurassic, salmonids from the Paleocene & Eocene, carp from the Cretaceous, and the great group of spiny teleosts from the Eocene. The first members of many of these families are known and are in the leptolepid family (note the inherent classification problem!).

Transition from primitive bony fish to amphibians
Few people realize that the fish-amphibian transition was not a transition from water to land. It was a transition from fins to feet that took place in the water. The very first amphibians seem to have developed legs and feet to scud around on the bottom in the water, as some modern fish do, not to walk on land (see Edwards, 1989). This aquatic-feet stage meant the fins didn't have to change very quickly, the weight-bearing limb musculature didn't have to be very well developed, and the axial musculature didn't have to change at all. Recently found fragmented fossils from the middle Upper Devonian, and new discoveries of late Upper Devonian feet (see below), support this idea of an "aquatic feet" stage. Eventually, of course, amphibians did move onto the land. This involved attaching the pelvis more firmly to the spine, and separating the shoulder from the skull. Lungs were not a problem, since lungs are an ancient fish trait and were present already.

Paleoniscoids again (e.g. Cheirolepis) -- These ancient bony fish probably gave rise both to modern ray-finned fish (mentioned above), and also to the lobe-finned fish.
Osteolepis (mid-Devonian) -- One of the earliest crossopterygian lobe-finned fishes, still sharing some characters with the lungfish (the other lobe-finned fishes). Had paired fins with a leg-like arrangement of major limb bones, capable of flexing at the "elbow", and had an early-amphibian-like skull and teeth.
Eusthenopteron, Sterropterygion (mid-late Devonian) -- Early rhipidistian lobe-finned fish roughly intermediate between early crossopterygian fish and the earliest amphibians. Eusthenopteron is best known, from an unusually complete fossil first found in 1881. Skull very amphibian-like. Strong amphibian- like backbone. Fins very like early amphibian feet in the overall layout of the major bones, muscle attachments, and bone processes, with tetrapod-like tetrahedral humerus, and tetrapod-like elbow and knee joints. But there are no perceptible "toes", just a set of identical fin rays. Body & skull proportions rather fishlike.
Panderichthys, Elpistostege (mid-late Devonian, about 370 Ma) -- These "panderichthyids" are very tetrapod-like lobe-finned fish. Unlike Eusthenopteron, these fish actually look like tetrapods in overall proportions (flattened bodies, dorsally placed orbits, frontal bones! in the skull, straight tails, etc.) and have remarkably foot-like fins.
Fragmented limbs and teeth from the middle Late Devonian (about 370 Ma), possibly belonging to Obruchevichthys -- Discovered in 1991 in Scotland, these are the earliest known tetrapod remains. The humerus is mostly tetrapod-like but retains some fish features. The discoverer, Ahlberg (1991), said: "It [the humerus] is more tetrapod-like than any fish humerus, but lacks the characteristic early tetrapod 'L-shape'...this seems to be a primitive, fish-like character....although the tibia clearly belongs to a leg, the humerus differs enough from the early tetrapod pattern to make it uncertain whether the appendage carried digits or a fin. At first sight the combination of two such extremities in the same animal seems highly unlikely on functional grounds. If, however, tetrapod limbs evolved for aquatic rather than terrestrial locomotion, as recently suggested, such a morphology might be perfectly workable."
GAP: Ideally, of course, we want an entire skeleton from the middle Late Devonian, not just limb fragments. Nobody's found one yet.

Hynerpeton, Acanthostega, and Ichthyostega (late Devonian) -- A little later, the fin-to-foot transition was almost complete, and we have a set of early tetrapod fossils that clearly did have feet. The most complete are Ichthyostega, Acanthostega gunnari, and the newly described Hynerpeton bassetti (Daeschler et al., 1994). (There are also other genera known from more fragmentary fossils.) Hynerpeton is the earliest of these three genera (365 Ma), but is more advanced in some ways; the other two genera retained more fish- like characters longer than the Hynerpeton lineage did.
Labyrinthodonts (eg Pholidogaster, Pteroplax) (late Dev./early Miss.) -- These larger amphibians still have some icthyostegid fish features, such as skull bone patterns, labyrinthine tooth dentine, presence & pattern of large palatal tusks, the fish skull hinge, pieces of gill structure between cheek & shoulder, and the vertebral structure. But they have lost several other fish features: the fin rays in the tail are gone, the vertebrae are stronger and interlocking, the nasal passage for air intake is well defined, etc.
More info on those first known Late Devonian amphibians: Acanthostega gunnari was very fish-like, and recently Coates & Clack (1991) found that it still had internal gills! They said: "Acanthostega seems to have retained fish-like internal gills and an open opercular chamber for use in aquatic respiration, implying that the earliest tetrapods were not fully terrestrial....Retention of fish-like internal gills by a Devonian tetrapod blurs the traditional distinction between tetrapods and fishes...this adds further support to the suggestion that unique tetrapod characters such as limbs with digits evolved first for use in water rather than for walking on land." Acanthostega also had a remarkably fish-like shoulder and forelimb. Ichthyostega was also very fishlike, retaining a fish-like finned tail, permanent lateral line system, and notochord. Neither of these two animals could have survived long on land.

Coates & Clack (1990) also recently found the first really well- preserved feet, from Acanthostega (front foot found) and Ichthyostega (hind foot found). (Hynerpeton's feet are unknown.) The feet were much more fin-like than anyone expected. It had been assumed that they had five toes on each foot, as do all modern tetrapods. This was a puzzle since the fins of lobe-finned fishes don't seem to be built on a five-toed plan. It turns out that Acanthostega's front foot had eight toes, and Ichthyostega's hind foot had seven toes, giving both feet the look of a short, stout flipper with many "toe rays" similar to fin rays. All you have to do to a lobe- fin to make it into a many-toed foot like this is curl it, wrapping the fin rays forward around the end of the limb. In fact, this is exactly how feet develop in larval amphibians, from a curled limb bud. (Also see Gould's essay on this subject, "Eight Little Piggies".) Said the discoverers (Coates & Clack, 1990): "The morphology of the limbs of Acanthostega and Ichthyostega suggest an aquatic mode of life, compatible with a recent assessment of the fish-tetrapod transition. The dorsoventrally compressed lower leg bones of Ichthyostega strongly resemble those of a cetacean [whale] pectoral flipper. A peculiar, poorly ossified mass lies anteriorly adjacent to the digits, and appears to be reinforcement for the leading edge of this paddle-like limb." Coates & Clack also found that Acanthostega's front foot couldn't bend forward at the elbow, and thus couldn't be brought into a weight-bearing position. In other words this "foot" still functioned as a horizontal fin. Ichthyostega's hind foot may have functioned this way too, though its front feet could take weight. Functionally, these two animals were not fully amphibian; they lived in an in-between fish/amphibian niche, with their feet still partly functioning as fins. Though they are probably not ancestral to later tetrapods, Acanthostega & Ichthyostega certainly show that the transition from fish to amphibian is feasible!

Hynerpeton, in contrast, probably did not have internal gills and already had a well-developed shoulder girdle; it could elevate and retract its forelimb strongly, and it had strong muscles that attached the shoulder to the rest of the body (Daeschler et al., 1994). Hynerpeton's discoverers think that since it had the strongest limbs earliest on, it may be the actual ancestor of all subsequent terrestrial tetrapods, while Acanthostega and Ichthyostega may have been a side branch that stayed happily in a mostly-aquatic niche.

In summary, the very first amphibians (presently known only from fragments) were probably almost totally aquatic, had both lungs and internal gills throughout life, and scudded around underwater with flipper-like, many-toed feet that didn't carry much weight. Different lineages of amphibians began to bend either the hind feet or front feet forward so that the feet carried weight. One line (Hynerpeton) bore weight on all four feet, developed strong limb girdles and muscles, and quickly became more terrestrial.

Transitions among amphibians
Temnospondyls, e.g Pholidogaster (Mississippian, about 330 Ma) -- A group of large labrinthodont amphibians, transitional between the early amphibians (the ichthyostegids, described above) and later amphibians such as rhachitomes and anthracosaurs. Probably also gave rise to modern amphibians (the Lissamphibia) via this chain of six temnospondyl genera , showing progressive modification of the palate, dentition, ear, and pectoral girdle, with steady reduction in body size (Milner, in Benton 198. Notice, though, that the times are out of order, though they are all from the Pennsylvanian and early Permian. Either some of the "Permian" genera arose earlier, in the Pennsylvanian (quite likely), and/or some of these genera are "cousins", not direct ancestors (also quite likely).
Dendrerpeton acadianum (early Penn.) -- 4-toed hand, ribs straight, etc.
Archegosaurus decheni (early Permian) -- Intertemporals lost, etc.
Eryops megacephalus (late Penn.) -- Occipital condyle splitting in 2, etc.
Trematops spp. (late Permian) -- Eardrum like modern amphibians, etc.
Amphibamus lyelli (mid-Penn.) -- Double occipital condyles, ribs very small, etc.
Doleserpeton annectens or perhaps Schoenfelderpeton (both early Permian) -- First pedicellate teeth! (a classic trait of modern amphibians) etc.
From there we jump to the Mesozoic:

Triadobatrachus (early Triassic) -- a proto-frog, with a longer trunk and much less specialized hipbone, and a tail still present (but very short).
Vieraella (early Jurassic) -- first known true frog.
Karaurus (early Jurassic) -- first known salamander.
Finally, here's a recently found fossil:

Unnamed proto-anthracosaur -- described by Bolt et al., 1988. This animal combines primitive features of palaeostegalians (e.g. temnospondyl-like vertebrae) with new anthracosaur-like features. Anthracosaurs were the group of large amphibians that are thought to have led, eventually, to the reptiles. Found in a new Lower Carboniferous site in Iowa, from about 320 Ma.    
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« Reply #1 on: September 14, 2005, 03:55:45 PM »

Transition from amphibians to amniotes (first reptiles)
The major functional difference between the ancient, large amphibians and the first little reptiles is the amniotic egg. Additional differences include stronger legs and girdles, different vertebrae, and stronger jaw muscles. For more info, see Carroll (198 and Gauthier et al. (in Benton, 198

Proterogyrinus or another early anthracosaur (late Mississippian) -- Classic labyrinthodont-amphibian skull and teeth, but with reptilian vertebrae, pelvis, humerus, and digits. Still has fish skull hinge. Amphibian ankle. 5-toed hand and a 2-3-4-5-3 (almost reptilian) phalangeal count.
Limnoscelis, Tseajaia (late Carboniferous) -- Amphibians apparently derived from the early anthracosaurs, but with additional reptilian features: structure of braincase, reptilian jaw muscle, expanded neural arches.
Solenodonsaurus (mid-Pennsylvanian) -- An incomplete fossil, apparently between the anthracosaurs and the cotylosaurs. Loss of palatal fangs, loss of lateral line on head, etc. Still just a single sacral vertebra, though.
Hylonomus, Paleothyris (early Pennsylvanian) -- These are protorothyrids, very early cotylosaurs (primitive reptiles). They were quite little, lizard-sized animals with amphibian-like skulls (amphibian pineal opening, dermal bone, etc.), shoulder, pelvis, & limbs, and intermediate teeth and vertebrae. Rest of skeleton reptilian, with reptilian jaw muscle, no palatal fangs, and spool-shaped vertebral centra. Probably no eardrum yet. Many of these new "reptilian" features are also seen in little amphibians (which also sometimes have direct-developing eggs laid on land), so perhaps these features just came along with the small body size of the first reptiles.
The ancestral amphibians had a rather weak skull and paired "aortas" (systemic arches). The first reptiles immediately split into two major lines which modified these traits in different ways. One line developed an aorta on the right side and strengthened the skull by swinging the quadrate bone down and forward, resulting in an enormous otic notch (and allowed the later development of good hearing without much further modification). This group further split into three major groups, easily recognizable by the number of holes or "fenestrae" in the side of the skull: the anapsids (no fenestrae), which produced the turtles; the diapsids (two fenestrae), which produced the dinosaurs and birds; and an offshoot group, the eurapsids (two fenestrae fused into one), which produced the ichthyosaurs.

The other major line of reptiles developed an aorta on left side only, and strengthened the skull by moving the quadrate bone up and back, obliterating the otic notch (making involvement of the jaw essential in the later development of good hearing). They developed a single fenestra per side. This group was the synapsid reptiles. They took a radically different path than the other reptiles, involving homeothermy, a larger brain, better hearing and more efficient teeth. One group of synapsids called the "therapsids" took these changes particularly far, and apparently produced the mammals.

Some transitions among reptiles
I will review just a couple of the reptile phylogenies, since there are so many.... Early reptiles to turtles: (Also see Gaffney & Meylan, in Benton 198

Captorhinus (early-mid Permain) -- Immediate descendent of the protorothryids.
Here we come to a controversy; there are two related groups of early anapsids, both descended from the captorhinids, that could have been ancestral to turtles. Reisz & Laurin (1991, 1993) believe the turtles descended from procolophonids, late Permian anapsids that had various turtle-like skull features. Others, particularly Lee (1993) think the turtle ancestors are pareiasaurs:

Scutosaurus and other pareiasaurs (mid-Permian) -- Large bulky herbivorous reptiles with turtle-like skull features. Several genera had bony plates in the skin, possibly the first signs of a turtle shell.
Deltavjatia vjatkensis (Permian) -- A recently discovered pareiasaur with numerous turtle-like skull features (e.g., a very high palate), limbs, and girdles, and lateral projections flaring out some of the vertebrae in a very shell-like way. (Lee, 1993)
Proganochelys (late Triassic) -- a primitive turtle, with a fully turtle-like skull, beak, and shell, but with some primitive traits such as rows of little palatal teeth, a still-recognizable clavicle, a simple captorhinid-type jaw musculature, a primitive captorhinid- type ear, a non-retractable neck, etc..
Recently discovered turtles from the early Jurassic, not yet described.
Mid-Jurassic turtles had already divided into the two main groups of modern turtles, the side-necked turtles and the arch-necked turtles. Obviously these two groups developed neck retraction separately, and came up with totally different solutions. In fact the first known arch-necked turtles, from the Late Jurassic, could not retract their necks, and only later did their descendents develop the archable neck. Early reptiles to diapsids: (see Evans, in Benton 1988, for more info)

Hylonomus, Paleothyris (early Penn.) -- The primitive amniotes described above
Petrolacosaurus, Araeoscelis (late Pennsylvanian) -- First known diapsids. Both temporal fenestra now present. No significant change in jaw muscles. Have Hylonomus-style teeth, with many small marginal teeth & two slightly larger canines. Still no eardrum.
Apsisaurus (early Permian) -- A more typical diapsid. Lost canines. (Laurin, 1991)
GAP: no diapsid fossils from the mid-Permian.

Claudiosaurus (late Permian) -- An early diapsid with several neodiapsid traits, but still had primitive cervical vertebrae & unossified sternum. probably close to the ancestry of all diapsides (the lizards & snakes & crocs & birds).
Planocephalosaurus(early Triassic) -- Further along the line that produced the lizards and snakes. Loss of some skull bones, teeth, toe bones.
Protorosaurus, Prolacerta (early Triassic) -- Possibly among the very first archosaurs, the line that produced dinos, crocs, and birds. May be "cousins" to the archosaurs, though.
Proterosuchus (early Triassic) -- First known archosaur.
Hyperodapedon, Trilophosaurus (late Triassic) -- Early archosaurs.
Some species-to-species transitions:

De Ricqles (in Chaline, 1983) documents several possible cases of gradual evolution (also well as some lineages that showed abrupt appearance or stasis) among the early Permian reptile genera Captorhinus, Protocaptorhinus, Eocaptorhinus, and Romeria.
Horner et al. (1992) recently found many excellent transitional dinosaur fossils from a site in Montana that was a coastal plain in the late Cretaceous. They include:
Many transitional ceratopsids between Styracosaurus and Pachyrhinosaurus
Many transitional lambeosaurids (50! specimens) between Lambeosaurus and Hypacrosaurus.
A transitional pachycephalosaurid between Stegoceras and Pachycephalosaurus
A transitional tyrannosaurid between Tyrannosaurus and Daspletosaurus.
All of these transitional animals lived during the same brief 500,000 years. Before this site was studied, these dinosaur groups were known from the much larger Judith River Formation, where the fossils showed 5 million years of evolutionary stasis, following by the apparently abrupt appearance of the new forms. It turns out that the sea level rose during that 500,000 years, temporarily burying the Judith River Formation under water, and forcing the dinosaur populations into smaller areas such as the site in Montana. While the populations were isolated in this smaller area, they underwent rapid evolution. When sea level fell again, the new forms spread out to the re-exposed Judith River landscape, thus appearing "suddenly" in the Judith River fossils, with the transitional fossils only existing in the Montana site. This is an excellent example of punctuated equilibrium (yes, 500,000 years is very brief and counts as a "punctuation"), and is a good example of why transitional fossils may only exist in a small area, with the new species appearing "suddenly" in other areas. (Horner et al., 1992) Also note the discovery of Ianthosaurus, a genus that links the two synapsid families Ophiacodontidae and Edaphosauridae. (see Carroll, 1988, p. 367)

Transition from synapsid reptiles to mammals
This is the best-documented transition between vertebrate classes. So far this series is known only as a series of genera or families; the transitions from species to species are not known. But the family sequence is quite complete. Each group is clearly related to both the group that came before, and the group that came after, and yet the sequence is so long that the fossils at the end are astoundingly different from those at the beginning. As Rowe recently said about this transition (in Szalay et al., 1993), "When sampling artifact is removed and all available character data analyzed [with computer phylogeny programs that do not assume anything about evolution], a highly corroborated, stable phylogeny remains, which is largely consistent with the temporal distributions of taxa recorded in the fossil record." Similarly, Gingerich has stated (1977) "While living mammals are well separated from other groups of animals today, the fossil record clearly shows their origin from a reptilian stock and permits one to trace the origin and radiation of mammals in considerable detail." For more details, see Kermack's superb and readable little book (1984), Kemp's more detailed but older book (1982), and read Szalay et al.'s recent collection of review articles (1993, vol. 1).

This list starts with pelycosaurs (early synapsid reptiles) and continues with therapsids and cynodonts up to the first unarguable "mammal". Most of the changes in this transition involved elaborate repackaging of an expanded brain and special sense organs, remodeling of the jaws & teeth for more efficient eating, and changes in the limbs & vertebrae related to active, legs-under-the-body locomotion. Here are some differences to keep an eye on:


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Early Reptiles/Mammals
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1 No fenestrae in skull / Massive fenestra exposes all of braincase

2 Braincase attached loosely / Braincase attached firmly to skull

3 No secondary palate / Complete bony secondary palate

4 Undifferentiated dentition / Incisors, canines, premolars, molars

5 Cheek teeth uncrowned / points Cheek teeth (PM & M) crowned & cusped

6 Teeth replaced continuously / Teeth replaced once at most

7 Teeth with single root / Molars double-rooted

8 Jaw joint quadrate-articular / Jaw joint dentary-squamosal (*)

9 Lower jaw of several bones / Lower jaw of dentary bone only

10 Single ear bone (stapes) / Three ear bones (stapes, incus, malleus)

11 Joined external nares / Separate external nares

12 Single occipital condyle / Double occipital condyle

13 Long cervical ribs / Cervical ribs tiny, fused to vertebrae

14 Lumbar region with ribs / Lumbar region rib-free

15 No diaphragm / Diaphragm

16 Limbs sprawled out from body / Limbs under body

17 Scapula simple / Scapula with big spine for muscles

18 Pelvic bones unfused / Pelvis fused

19 Two sacral (hip) vertebrae / Three or more sacral vertebrae

20 Toe bone #'s 2-3-4-5-4 / Toe bones 2-3-3-3-3

21 Body temperature variable / Body temperature constant
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(*) The presence of a dentary-squamosal jaw joint has been arbitrarily selected as the defining trait of a mammal.

Paleothyris (early Pennsylvanian) -- An early captorhinomorph reptile, with no temporal fenestrae at all.
Protoclepsydrops haplous (early Pennsylvanian) -- The earliest known synapsid reptile. Little temporal fenestra, with all surrounding bones intact. Fragmentary. Had amphibian-type vertebrae with tiny neural processes. (reptiles had only just separated from the amphibians)
Clepsydrops (early Pennsylvanian) -- The second earliest known synapsid. These early, very primitive synapsids are a primitive group of pelycosaurs collectively called "ophiacodonts".
Archaeothyris (early-mid Pennsylvanian) -- A slightly later ophiacodont. Small temporal fenestra, now with some reduced bones (supratemporal). Braincase still just loosely attached to skull. Slight hint of different tooth types. Still has some extremely primitive, amphibian/captorhinid features in the jaw, foot, and skull. Limbs, posture, etc. typically reptilian, though the ilium (major hip bone) was slightly enlarged.
Varanops (early Permian) -- Temporal fenestra further enlarged. Braincase floor shows first mammalian tendencies & first signs of stronger attachment to rest of skull (occiput more strongly attached). Lower jaw shows first changes in jaw musculature (slight coronoid eminence). Body narrower, deeper: vertebral column more strongly constructed. Ilium further enlarged, lower-limb musculature starts to change (prominent fourth trochanter on femur). This animal was more mobile and active. Too late to be a true ancestor, and must be a "cousin".
Haptodus (late Pennsylvanian) -- One of the first known sphenacodonts, showing the initiation of sphenacodont features while retaining many primitive features of the ophiacodonts. Occiput still more strongly attached to the braincase. Teeth become size-differentiated, with biggest teeth in canine region and fewer teeth overall. Stronger jaw muscles. Vertebrae parts & joints more mammalian. Neural spines on vertebrae longer. Hip strengthened by fusing to three sacral vertebrae instead of just two. Limbs very well developed.
Dimetrodon, Sphenacodon or a similar sphenacodont (late Pennsylvanian to early Permian, 270 Ma) -- More advanced pelycosaurs, clearly closely related to the first therapsids (next). Dimetrodon is almost definitely a "cousin" and not a direct ancestor, but as it is known from very complete fossils, it's a good model for sphenacodont anatomy. Medium-sized fenestra. Teeth further differentiated, with small incisors, two huge deep- rooted upper canines on each side, followed by smaller cheek teeth, all replaced continuously. Fully reptilian jaw hinge. Lower jaw bone made of multiple bones & with first signs of a bony prong later involved in the eardrum, but there was no eardrum yet, so these reptiles could only hear ground-borne vibrations (they did have a reptilian middle ear). Vertebrae had still longer neural spines (spectacularly so in Dimetrodon, which had a sail), and longer transverse spines for stronger locomotion muscles.
Biarmosuchia (late Permian) -- A therocephalian -- one of the earliest, most primitive therapsids. Several primitive, sphenacodontid features retained: jaw muscles inside the skull, platelike occiput, palatal teeth. New features: Temporal fenestra further enlarged, occupying virtually all of the cheek, with the supratemporal bone completely gone. Occipital plate slanted slightly backwards rather than forwards as in pelycosaurs, and attached still more strongly to the braincase. Upper jaw bone (maxillary) expanded to separate lacrymal from nasal bones, intermediate between early reptiles and later mammals. Still no secondary palate, but the vomer bones of the palate developed a backward extension below the palatine bones. This is the first step toward a secondary palate, and with exactly the same pattern seen in cynodonts. Canine teeth larger, dominating the dentition. Variable tooth replacement: some therocephalians (e.g Scylacosaurus) had just one canine, like mammals, and stopped replacing the canine after reaching adult size. Jaw hinge more mammalian in position and shape, jaw musculature stronger (especially the mammalian jaw muscle). The amphibian-like hinged upper jaw finally became immovable. Vertebrae still sphenacodontid-like. Radical alteration in the method of locomotion, with a much more mobile forelimb, more upright hindlimb, & more mammalian femur & pelvis. Primitive sphenacodontid humerus. The toes were approaching equal length, as in mammals, with #toe bones varying from reptilian to mammalian. The neck & tail vertebrae became distinctly different from trunk vertebrae. Probably had an eardrum in the lower jaw, by the jaw hinge.
Procynosuchus (latest Permian) -- The first known cynodont -- a famous group of very mammal-like therapsid reptiles, sometimes considered to be the first mammals. Probably arose from the therocephalians, judging from the distinctive secondary palate and numerous other skull characters. Enormous temporal fossae for very strong jaw muscles, formed by just one of the reptilian jaw muscles, which has now become the mammalian masseter. The large fossae is now bounded only by the thin zygomatic arch (cheekbone to you & me). Secondary palate now composed mainly of palatine bones (mammalian), rather than vomers and maxilla as in older forms; it's still only a partial bony palate (completed in life with soft tissue). Lower incisor teeth was reduced to four (per side), instead of the previous six (early mammals had three). Dentary now is 3/4 of lower jaw; the other bones are now a small complex near the jaw hinge. Jaw hinge still reptilian. Vertebral column starts to look mammalian: first two vertebrae modified for head movements, and lumbar vertebrae start to lose ribs, the first sign of functional division into thoracic and lumbar regions. Scapula beginning to change shape. Further enlargement of the ilium and reduction of the pubis in the hip. A diaphragm may have been present.
Dvinia [also "Permocynodon"] (latest Permian) -- Another early cynodont. First signs of teeth that are more than simple stabbing points -- cheek teeth develop a tiny cusp. The temporal fenestra increased still further. Various changes in the floor of the braincase; enlarged brain. The dentary bone was now the major bone of the lower jaw. The other jaw bones that had been present in early reptiles were reduced to a complex of smaller bones near the jaw hinge. Single occipital condyle splitting into two surfaces. The postcranial skeleton of Dvinia is virtually unknown and it is not therefore certain whether the typical features found at the next level had already evolved by this one. Metabolic rate was probably increased, at least approaching homeothermy.
Thrinaxodon (early Triassic) -- A more advanced "galesaurid" cynodont. Further development of several of the cynodont features seen already. Temporal fenestra still larger, larger jaw muscle attachments. Bony secondary palate almost complete. Functional division of teeth: incisors (four uppers and three lowers), canines, and then 7-9 cheek teeth with cusps for chewing. The cheek teeth were all alike, though (no premolars & molars), did not occlude together, were all single- rooted, and were replaced throughout life in alternate waves. Dentary still larger, with the little quadrate and articular bones were loosely attached. The stapes now touched the inner side of the quadrate. First sign of the mammalian jaw hinge, a ligamentous connection between the lower jaw and the squamosal bone of the skull. The occipital condyle is now two slightly separated surfaces, though not separated as far as the mammalian double condyles. Vertebral connections more mammalian, and lumbar ribs reduced. Scapula shows development of a new mammalian shoulder muscle. Ilium increased again, and all four legs fully upright, not sprawling. Tail short, as is necessary for agile quadrupedal locomotion. The whole locomotion was more agile. Number of toe bones is 2.3.4.4.3, intermediate between reptile number (2.3.4.5.4) and mammalian (2.3.3.3.3), and the "extra" toe bones were tiny. Nearly complete skeletons of these animals have been found curled up - a possible reaction to conserve heat, indicating possible endothermy? Adults and juveniles have been found together, possibly a sign of parental care. The specialization of the lumbar area (e.g. reduction of ribs) is indicative of the presence of a diaphragm, needed for higher O2 intake and homeothermy. NOTE on hearing: The eardrum had developed in the only place available for it -- the lower jaw, right near the jaw hinge, supported by a wide prong (reflected lamina) of the angular bone. These animals could now hear airborne sound, transmitted through the eardrum to two small lower jaw bones, the articular and the quadrate, which contacted the stapes in the skull, which contacted the cochlea. Rather a roundabout system and sensitive to low-frequency sound only, but better than no eardrum at all! Cynodonts developed quite loose quadrates and articulars that could vibrate freely for sound transmittal while still functioning as a jaw joint, strengthened by the mammalian jaw joint right next to it. All early mammals from the Lower Jurassic have this low-frequency ear and a double jaw joint. By the middle Jurassic, mammals lost the reptilian joint (though it still occurs briefly in embryos) and the two bones moved into the nearby middle ear, became smaller, and became much more sensitive to high-frequency sounds.
Cynognathus (early Triassic, 240 Ma; suspected to have existed even earlier) -- We're now at advanced cynodont level. Temporal fenestra larger. Teeth differentiating further; cheek teeth with cusps met in true occlusion for slicing up food, rate of replacement reduced, with mammalian-style tooth roots (though single roots). Dentary still larger, forming 90% of the muscle-bearing part of the lower jaw. TWO JAW JOINTS in place, mammalian and reptilian: A new bony jaw joint existed between the squamosal (skull) and the surangular bone (lower jaw), while the other jaw joint bones were reduced to a compound rod lying in a trough in the dentary, close to the middle ear. Ribs more mammalian. Scapula halfway to the mammalian condition. Limbs were held under body. There is possible evidence for fur in fossil pawprints.
Diademodon (early Triassic, 240 Ma; same strata as Cynognathus) -- Temporal fenestra larger still, for still stronger jaw muscles. True bony secondary palate formed exactly as in mammals, but didn't extend quite as far back. Turbinate bones possibly present in the nose (warm-blooded?). Dental changes continue: rate of tooth replacement had decreased, cheek teeth have better cusps & consistent wear facets (better occlusion). Lower jaw almost entirely dentary, with tiny articular at the hinge. Still a double jaw joint. Ribs shorten suddenly in lumbar region, probably improving diaphragm function & locomotion. Mammalian toe bones (2.3.3.3.3), with closely related species still showing variable numbers.
Probelesodon (mid-Triassic; South America) -- Fenestra very large, still separate from eyesocket (with postorbital bar). Secondary palate longer, but still not complete. Teeth double-rooted, as in mammals. Nares separated. Second jaw joint stronger. Lumbar ribs totally lost; thoracic ribs more mammalian, vertebral connections very mammalian. Hip & femur more mammalian.
Probainognathus (mid-Triassic, 239-235 Ma, Argentina) -- Larger brain with various skull changes: pineal foramen ("third eye") closes, fusion of some skull plates. Cheekbone slender, low down on the side of the eye socket. Postorbital bar still there. Additional cusps on cheek teeth. Still two jaw joints. Still had cervical ribs & lumbar ribs, but they were very short. Reptilian "costal plates" on thoracic ribs mostly lost. Mammalian #toe bones.
Exaeretodon (mid-late Triassic, 239Ma, South America) -- (Formerly lumped with the herbivorous gomphodont cynodonts.) Mammalian jaw prong forms, related to eardrum support. Three incisors only (mammalian). Costal plates completely lost. More mammalian hip related to having limbs under the body. Possibly the first steps toward coupling of locomotion & breathing. This is probably a "cousin" fossil not directly ancestral, as it has several new but non-mammalian teeth traits.
GAP of about 30 my in the late Triassic, from about 239-208 Ma. Only one early mammal fossil is known from this time. The next time fossils are found in any abundance, tritylodontids and trithelodontids had already appeared, leading to some very heated controversy about their relative placement in the chain to mammals. Recent discoveries seem to show trithelodontids to be more mammal- like, with tritylodontids possibly being an offshoot group (see Hopson 1991, Rowe 1988, Wible 1991, and Shubin et al. 1991). Bear in mind that both these groups were almost fully mammalian in every feature, lacking only the final changes in the jaw joint and middle ear.

Oligokyphus, Kayentatherium (early Jurassic, 208 Ma) -- These are tritylodontids, an advanced cynodont group. Face more mammalian, with changes around eyesocket and cheekbone. Full bony secondary palate. Alternate tooth replacement with double-rooted cheek teeth, but without mammalian-style tooth occlusion (which some earlier cynodonts already had). Skeleton strikingly like egg- laying mammals (monotremes). Double jaw joint. More flexible neck, with mammalian atlas & axis and double occipital condyle. Tail vertebrae simpler, like mammals. Scapula is now substantially mammalian, and the forelimb is carried directly under the body. Various changes in the pelvis bones and hind limb muscles; this animal's limb musculature and locomotion were virtually fully mammalian. Probably cousin fossils (?), with Oligokyphus being more primitive than Kayentatherium. Thought to have diverged from the trithelodontids during that gap in the late Triassic. There is disagreement about whether the tritylodontids were ancestral to mammals (presumably during the late Triassic gap) or whether they are a specialized offshoot group not directly ancestral to mammals.
Pachygenelus, Diarthrognathus (earliest Jurassic, 209 Ma) -- These are trithelodontids, a slightly different advanced cynodont group. New discoveries (Shubin et al., 1991) show that these animals are very close to the ancestry of mammals. Inflation of nasal cavity, establishment of Eustachian tubes between ear and pharynx, loss of postorbital bar. Alternate replacement of mostly single- rooted teeth. This group also began to develop double tooth roots -- in Pachygenelus the single root of the cheek teeth begins to split in two at the base. Pachygenelus also has mammalian tooth enamel, and mammalian tooth occlusion. Double jaw joint, with the second joint now a dentary-squamosal (instead of surangular), fully mammalian. Incipient dentary condyle. Reptilian jaw joint still present but functioning almost entirely in hearing; postdentary bones further reduced to tiny rod of bones in jaw near middle ear; probably could hear high frequencies now. More mammalian neck vertebrae for a flexible neck. Hip more mammalian, with a very mammalian iliac blade & femur. Highly mobile, mammalian-style shoulder. Probably had coupled locomotion & breathing. These are probably "cousin" fossils, not directly ancestral (the true ancestor is thought to have occurred during that late Triassic gap). Pachygenelus is pretty close, though.
Adelobasileus cromptoni (late Triassic; 225 Ma, west Texas) -- A recently discovered fossil proto-mammal from right in the middle of that late Triassic gap! Currently the oldest known "mammal." Only the skull was found. "Some cranial features of Adelobasileus, such as the incipient promontorium housing the cochlea, represent an intermediate stage of the character transformation from non-mammalian cynodonts to Liassic mammals" (Lucas & Luo, 1993). This fossil was found from a band of strata in the western U.S. that had not previously been studied for early mammals. Also note that this fossil dates from slightly before the known tritylodonts and trithelodonts, though it has long been suspected that tritilodonts and trithelodonts were already around by then. Adelobasileus is thought to have split off from either a trityl. or a trithel., and is either identical to or closely related to the common ancestor of all mammals.
Sinoconodon (early Jurassic, 208 Ma) -- The next known very ancient proto-mammal. Eyesocket fully mammalian now (closed medial wall). Hindbrain expanded. Permanent cheekteeth, like mammals, but the other teeth were still replaced several times. Mammalian jaw joint stronger, with large dentary condyle fitting into a distinct fossa on the squamosal. This final refinement of the joint automatically makes this animal a true "mammal". Reptilian jaw joint still present, though tiny.
Kuehneotherium (early Jurassic, about 205 Ma) -- A slightly later proto-mammal, sometimes considered the first known pantothere (primitive placental-type mammal). Teeth and skull like a placental mammal. The three major cusps on the upper & lower molars were rotated to form interlocking shearing triangles as in the more advanced placental mammals & marsupials. Still has a double jaw joint, though.
Eozostrodon, Morganucodon, Haldanodon (early Jurassic, ~205 Ma) -- A group of early proto-mammals called "morganucodonts". The restructuring of the secondary palate and the floor of the braincase had continued, and was now very mammalian. Truly mammalian teeth: the cheek teeth were finally differentiated into simple premolars and more complex molars, and teeth were replaced only once. Triangular- cusped molars. Reversal of the previous trend toward reduced incisors, with lower incisors increasing to four. Tiny remnant of the reptilian jaw joint. Once thought to be ancestral to monotremes only, but now thought to be ancestral to all three groups of modern mammals -- monotremes, marsupials, and placentals.
Peramus (late Jurassic, about 155 Ma) -- A "eupantothere" (more advanced placental-type mammal). The closest known relative of the placentals & marsupials. Triconodont molar has with more defined cusps. This fossil is known only from teeth, but judging from closely related eupantotheres (e.g. Amphitherium) it had finally lost the reptilian jaw joint, attaing a fully mammalian three-boned middle ear with excellent high-frequency hearing. Has only 8 cheek teeth, less than other eupantotheres and close to the 7 of the first placental mammals. Also has a large talonid on its "tribosphenic" molars, almost as large as that of the first placentals -- the first development of grinding capability.
Endotherium (very latest Jurassic, 147 Ma) -- An advanced eupantothere. Fully tribosphenic molars with a well- developed talonid. Known only from one specimen. From Asia; recent fossil finds in Asia suggest that the tribosphenic molar evolved there.
Kielantherium and Aegialodon (early Cretaceous) -- More advanced eupantotheres known only from teeth. Kielantherium is from Asia and is known from slightly older strata than the European Aegialodon. Both have the talonid on the lower molars. The wear on it indicates that a major new cusp, the protocone, had evolved on the upper molars. By the Middle Cretaceous, animals with the new tribosphenic molar had spread into North America too (North America was still connected to Europe.)
Steropodon galmani (early Cretaceous) -- The first known definite monotreme, discovered in 1985.
Vincelestes neuquenianus (early Cretaceous, 135 Ma) -- A probably-placental mammal with some marsupial traits, known from some nice skulls. Placental-type braincase and coiled cochlea. Its intracranial arteries & veins ran in a composite monotreme/placental pattern derived from homologous extracranial vessels in the cynodonts. (Rougier et al., 1992)
Pariadens kirklandi (late Cretaceous, about 95 Ma) -- The first definite marsupial. Known only from teeth.
Kennalestes and Asioryctes (late Cretaceous, Mongolia) -- Small, slender animals; eyesocket open behind; simple ring to support eardrum; primitive placental-type brain with large olfactory bulbs; basic primitive tribosphenic tooth pattern. Canine now double rooted. Still just a trace of a non-dentary bone, the coronoid, on the otherwise all-dentary jaw. "Could have given rise to nearly all subsequent placentals." says Carroll (198.
Cimolestes, Procerberus, Gypsonictops (very late Cretaceous) -- Primitive North American placentals with same basic tooth pattern.
So, by the late Cretaceous the three groups of modern mammals were in place: monotremes, marsupials, and placentals. Placentals appear to have arisen in East Asia and spread to the Americas by the end of the Cretaceous. In the latest Cretaceous, placentals and marsupials had started to diversify a bit, and after the dinosaurs died out, in the Paleocene, this diversification accelerated. For instance, in the mid- Paleocene the placental fossils include a very primitive primate-like animal (Purgatorius - known only from a tooth, though, and may actually be an early ungulate), a herbivore-like jaw with molars that have flatter tops for better grinding (Protungulatum, probably an early ungulate), and an insectivore (Paranyctoides).

The decision as to which was the first mammal is somewhat subjective. We are placing an inflexible classification system on a gradational series. What happened was that an intermediate group evolved from the 'true' reptiles, which gradually acquired mammalian characters until a point was reached where we have artificially drawn a line between reptiles and mammals. For instance, Pachygenulus and Kayentatherium are both far more mammal-like than reptile-like, but they are both called "reptiles".
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« Reply #2 on: September 14, 2005, 03:59:36 PM »

Transition from diapsid reptiles to birds
In the mid-1800's, this was one of the most significant gaps in vertebrate fossil evolution. No transitional fossils at all were known, and the two groups seemed impossibly different. Then the exciting discovery of Archeopteryx in 1861 showed clearly that the two groups were in fact related. Since then, some other reptile-bird links have been found. On the whole, though, this is still a gappy transition, consisting of a very large-scale series of "cousin" fossils. I have not included Mononychus (as it appears to be a digger, not a flier, well off the line to modern birds). See Feduccia (1980) and Rayner (1989) for more discussion of the evolution of flight, and Chris Nedin's excellent Archeopteryx FAQ for more info on that critter.

Coelophysis (late Triassic) -- One of the first theropod dinosaurs. Theropods in general show clear general skeletal affinities with birds (long limbs, hollow bones, foot with 3 toes in front and 1 reversed toe behind, long ilium). Jurassic theropods like Compsognathus are particularly similar to birds.
Deinonychus, Oviraptor, and other advanced theropods (late Jurassic, Cretaceous) -- Predatory bipedal advanced theropods, larger, with more bird-like skeletal features: semilunate carpal, bony sternum, long arms, reversed pubis. Clearly runners, though, not fliers. These advanced theropods even had clavicles, sometimes fused as in birds. Says Clark (1992): "The detailed similarity between birds and theropod dinosaurs such as Deinonychus is so striking and so pervasive throughout the skeleton that a considerable amount of special pleading is needed to come to any conclusion other than that the sister-group of birds among fossils is one of several theropod dinosaurs." The particular fossils listed here are are not directly ancestral, though, as they occur after Archeopteryx.
Lisboasaurus estesi & other "troodontid dinosaur-birds" (mid-Jurassic) -- A bird-like theropod reptile with very bird-like teeth (that is, teeth very like those of early toothed birds, since modern birds have no teeth). These really could be ancestral.
GAP: The exact reptilian ancestor of Archeopteryx, and the first development of feathers, are unknown. Early bird evolution seems to have involved little forest climbers and then little forest fliers, both of which are guaranteed to leave very bad fossil records (little animal + acidic forest soil = no remains). Archeopteryx itself is really about the best we could ask for: several specimens has superb feather impressions, it is clearly related to both reptiles and birds, and it clearly shows that the transition is feasible.

One possible ancestor of Archeopteryx is Protoavis (Triassic, ~225 Ma) -- A highly controversial fossil that may or may not be an extremely early bird. Unfortunately, not enough of the fossil was recovered to determine if it is definitely related to the birds.
Archeopteryx lithographica (Late Jurassic, 150 Ma) -- The several known specimes of this deservedly famous fossil show a mosaic of reptilian and avian features, with the reptilian features predominating. The skull and skeleton are basically reptilian (skull, teeth, vertebrae, sternum, ribs, pelvis, tail, digits, claws, generally unfused bones). Bird traits are limited to an avian furcula (wishbone, for attachment of flight muscles; recall that at least some dinosaurs had this too), modified forelimbs, and -- the real kicker -- unmistakable lift-producing flight feathers. Archeopteryx could probably flap from tree to tree, but couldn't take off from the ground, since it lacked a keeled breastbone for large flight muscles, and had a weak shoulder compared to modern birds. May not have been the direct ancestor of modern birds. (Wellnhofer, 1993)
Sinornis santensis ("Chinese bird", early Cretaceous, 138 Ma) -- A recently found little primitive bird. Bird traits: short trunk, claws on the toes, flight-specialized shoulders, stronger flight- feather bones, tightly folding wrist, short hand. (These traits make it a much better flier than Archeopteryx.) Reptilian traits: teeth, stomach ribs, unfused hand bones, reptilian-shaped unfused pelvis. (These remaining reptilian traits wouldn't have interfered with flight.) Intermediate traits: metatarsals partially fused, medium-sized sternal keel, medium-length tail (8 vertebrae) with fused pygostyle at the tip. (Sereno & Rao, 1992).
"Las Hoyas bird" or "Spanish bird" [not yet named; early Cretaceous, 131 Ma) -- Another recently found "little forest flier". It still has reptilian pelvis & legs, with bird-like shoulder. Tail is medium-length with a fused tip. A fossil down feather was found with the Las Hoyas bird, indicating homeothermy. (Sanz et al., 1992)
Ambiortus dementjevi (early Cretaceous, 125 Ma) -- The third known "little forest flier", found in 1985. Very fragmentary fossil.
Hesperornis, Ichthyornis, and other Cretaceous diving birds -- This line of birds became specialized for diving, like modern cormorants. As they lived along saltwater coasts, there are many fossils known. Skeleton further modified for flight (fusion of pelvis bones, fusion of hand bones, short & fused tail). Still had true socketed teeth, a reptilian trait.
[Note: a classic study of chicken embryos showed that chicken bills can be induced to develop teeth, indicating that chickens (and perhaps other modern birds) still retain the genes for making teeth. Also note that molecular data shows that crocodiles are birds' closest living relatives.]
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« Reply #3 on: September 14, 2005, 04:38:46 PM »

Mammal-Like Reptiles

As previously stated, a succession of transitional fossils exists that link reptiles (Class Reptilia) and mammals (Class Mammalia). These particular reptiles are classifie as Subclass Synapsida. Presently, this is the best example of th e transformation of one major higher taxon into another. The morphologic changes that took place are well documented by fossils, beginning with animals essentially 100% reptilian and resulting in animals essentially 100% mammalian. See the chart below...

Modern reptiles and mammals are very distinctive, easily diagnosable, and do not intergrade. Reptiles are covered by scales, mammals by hair; reptiles are cold-blooded, mammals warm-blooded; reptiles do not suckle their young, mammals have mammary glands; reptiles have sprawling posture, mammals have upright posture. Most of these features are soft part anatomy or physiology that very rarely fossilize (although dinosaur skin impressions are known from Cretaceous sediments, and imprints of mammal hair are known from Eocene bats from Germany; Franzen, 1990). In the fossil record, we must look to skeletal features.


There are many skeletal features which allow us to distinguish the reptiles from the mammals (Carroll, 1988; Table 1, rows A, M). The single most important defining characteristic is the nature of the articulation of the lower jaw to the skull (Simpson, 1959). In reptiles, multiple bones comprise the lower jaw. A small bone at the posterior end of the lower jaw, the articular, articulates with the quadrate bone of the skull (Simpson, 1959; Carroll, 198. In mammals, one large bone, the dentary, comprises the lower jaw. It articulates with the squamosal bone of the skull (Simpson, 1959; Carroll, 198.


From comparative anatomy studies, it is certain that most of the bones of the reptiles and mammals are homologous (Crompton & Parker, 1978; Carroll, 198. Of greatest importance, the middle ear bones of mammals (stapes, incus, malleus, and tympanic) are homologous with several of the skull and jaw bones of reptiles (stapes, quadrate, articular, and angular, respectively; Romer, 1956, p. 33-38, 1970a; Allin, 1975, 1986; Allin & Hopson, 1992; Crompton & Parker, 1978; Hopso n, 1987, 1994; Carroll, 198. One group of reptiles, the synapsids (Subclass Synapsida), share with the mammals an additional homologous structure: the lateral temporal fenestra, which is an opening in the skull behind the eye socket at the triple junction between the squamosal, jugal , and post orbital bones (Broom, 1932; Frazetta, 1968; Kemp, 1982; Carroll, 198. A band of bone composed of the jugal and the squamosal is adjacent to the lateral temporal fenestra (Broom, 1932; Kemp, 1982; Carroll, 198. This is the cheek arch so characteristic of mammal skulls (Broom, 1932; Kemp, 1982; Carroll, 198. Therefore, synapsids are commonly named the “mammal-like reptiles.”


The presence of diagnosable morphologic differences between reptiles (including the oldest reptiles and the oldest synapsids) and mammals distinguishes them as distinct taxa. This allows us to test evolution by looking for transitional forms between the two. Because many of the bones are homologous, we should find evidence illustrating how these bones were modified over time to become the new bones. Furthermore, these morphologic changes should happen in parallel and in geochronologic succession.


Synapsid reptiles inhabited Pangea from the Middle Pennsylvanian through the Early Jurassic (Kemp, 1982, 1985; Sloan, 1983; Carroll, 1988; Hopson, 1969, 1987, 1994; Hopson & Crompton, 1969; Hotton, et al., 1986; Crompton & Jenkins, 1973; Sidor & Hopson, 1998; Romer & Price, 1940; Broom, 1932; Boonstra, 1963, 1969, 1971; Tchudinov, 1983; Olson, 1944; Tatarinov, 1974; Vyushkov, 1955; Efremov, 1954). From the Early Permian through the Early Triassic, they were the largest and most abundant land animals (Sloan, 1983; Colbert, 1965). Though much less well known to the general public than dinosaurs, one of the “cereal box dinosaurs,” Dimetrodon (the sail-backed reptile), is a synapsid, not a dinosaur (Romer & Price, 1940; Carroll, 198. The oldest mammals are Late Triassic (Kemp, 1982; Carroll, 198. Below is a discussion of the geochronologic succession linking synapsids and mammals. The oldest reptiles (named protorothyrids; Carroll, 1964, 1988, p. 192-199) are from the lower Middle Pennsylvanian, and the oldest synapsids (Reisz, 1972) are from the upper Middle Pennsylvanian, both of Nova Scotia. Upper Pennsylvanian and Lower Permian forms are known primarily from the midcontinent and Permian Basin region of the United States (Romer & Price, 1940; Currie, 1977, 1979; Kemp, 1982; Sloan, 1983). The basal Upper Permian forms are known from Russia (Tchudinov, 1960, 1983; Efremov, 1954; Olson, 1962; Sigogneau & Tchudinov, 1972; Ivakhnenko et al., 1997). Most of the Upper Permian and Lower Triassic succession is known from southern Africa, especially the Great Karoo of South Africa (Broom, 1932; Boonstra, 1963, 1969, 1971; Hopson & Kitching, 1972; Kemp, 1982; Sloan, 1983). The Middle Triassic forms are from South America (Romer, 1969a, 1969b, 1970b, 1973; Romer & Lewis, 1973; Bonaparte & Barbarena, 1975), and the Upper Triassic and Lower Jurassic mammals are known from Eurasia (Kermack, Mussett, & Rigney, 1973, 1981; Kemp, 1982). Subsequent Mesozoic mammals are known from all over the world (Simpson, 1928; Lillegraven et al., 1979).


When placed in proper geochronologic succession, the synapsids naturally form a succession of taxa (genera and families) that progressively become more mammal-like and less reptile-like (Kemp, 1982, 1985; Sloan, 1983; Sidor & Hopson, 1998; Hopson, 1987, 1994). Morphologic changes, summarized in Table 1 and Figure 1, affect the entire skeletal anatomy of these animals, but are most clearly displayed in their skulls.


The lateral temporal fenestra increased in size from a tiny opening smaller than the eye socket to a giant opening occupying nearly half the length of the skull. Ultimately, it merged with the eye socket, thus producing the full development of the cheek arch so characteristic of mammals (Broom, 1932; Frazetta, 1968; Kemp, 1982; Sloan, 1983; Hopson, 1987, 1994; Carroll, 198.


Successively, the relative proportion of the lower jaw comprised of the dentary bone (teeth-bearing bone) gradually increased until the entire lower jaw consisted of the dentary (Kemp, 1982; Sloan, 1983; Carroll, 1988; Hopson, 1987, 1994). In Pennsylvanian and Lower and basal Upper Permian synapsids, the postero-dorsal edge of the lower jaw rose broadly but only slightly above the level of the tooth row (Romer & Price, 1940; Currie, 1977, 1979; Ivakhnenko et al., 1997; Tchudinov, 1960, 1983; Efremov, 1954; Olson, 1962; Sigogneau & Tchudinov, 1972; Hopson, 1987, 1994). In succeeding forms, the posterior part of the dentary expanded dorsally and posteriorly as a blade-like process, and progressively became larger (Broom, 1932; Boonstra, 1963, 1969, 1971; Sigogneau, 1970; Brink, 1963; Kemp, 1979; Hopson, 1987, 1994), forming the coronoid process (Parrington, 1946; Fourie, 1974; Romer, 1969b, 1970b, 1973; Hopson, 1987, 1994) to which the mammalian-type jaw musculature is attached (Barghusen, 1968; Bramble, 1978; Crompton, 1972; Crompton & Parker, 1978; Kemp, 1982; Sloan, 1983; Carroll, 198. Concomitantly, the post-dentary bones progressively reduced in size (Allin, 1975; Crompton, 1972; Crompton & Parker, 1978; Kemp, 1982; Sloan, 1983; Carroll, 1988; Hopson, 1987, 1994).


Beginning with the Upper Pennsylvanian sphenacodonts, a notch developed in the angular bone that offsets a projection, the reflected lamina (Allin, 1975; Allin & Hopson, 1992; Hopson, 1987, 1994; Romer & Price, 1940; Currie, 1977, 1979; Kemp, 1982; Sloan, 1983; Carroll, 198. The reflected lamina first became a large blade-like flange (Allin, 1975; Allin & Hopson, 1992; Hopson, 1987, 1994; Ivakhnenko et al., 1997; Tchudinov, 1960, 1983; Efremov, 1954; Olson, 1962; Sigogneau & Tchudinov, 1972; Broom, 1932; Sigogneau, 1970; Boonstra, 1963, 1969, 1971), and then was progressively reduced to a delicate horseshoe-shaped bone (Allin, 1975; Allin & Hopson, 1992; Hopson, 1987, 1994; Brink, 1963; Parrington, 1946; Fourie, 1974; Romer, 1969b, 1970b, 1973; Kermack, Mussett, & Rigney, 1973, 1981; Kemp, 1979, 1982; Sloan, 1983; Carroll, 198.


Simultaneously, the quadrate progressively decreased in size (Allin, 1975; Allin & Hopson, 1992; Hopson, 1987, 1994; Kemp, 1982; Sloan, 1983; Carroll, 198. The articular did not decrease in size much, being small initially, but developed a downward-pointing prong (Allin, 1975; Allin & Hopson, 1992; Hopson, 1987, 1994; Kemp, 1982; Sloan, 1983; Carroll, 198. In the synapsids, the lower jaw was hinged to the skull by the articular and quadrate bones (Crompton, 1972; Crompton & Parker, 1978; Allin, 1975; Allin & Hopson, 1992; Hopson, 1987, 1994). Thus they are classified as reptiles (Simpson, 1959; Kemp, 1982; Sloan, 1983; Carroll, 198. As the quadrate and articular became smaller, they were relieved of their solid suture to the dentary and skull (Crompton, 1972; Allin, 1975, 1986; Allin & Hopson, 1992; Hopson, 1987, 1994; Crompton & Parker, 1978; Kemp, 1982; Sloan, 1983; Carroll, 198. A projection of the dentary extended posteriorly and made contact with the squamosal. Morganucodon possessed the mammalian dentary-squamosal jaw joint adjacent to the reptilian articular-quadrate jaw joint (Kermack, Mussett, & Rigney, 1973, 1981; Carroll, 198. It is classified as the first mammal, but it is a perfect intermediate. Now that a new jaw joint was established, the quadrate and articular were subsequently relieved of that function (Crompton, 1972; Allin, 1975, 1986; Allin & Hopson, 1992; Hopson, 1987, 1994; Crompton & Parker, 1978; Kemp, 1982; Sloan, 1983; Carroll, 198. Ultimately, in Middle and Upper Jurassic mammals, the tiny quadrate, articular, and ring-like angular migrated as a unit to the middle ear where they joined the stapes and became the incus, malleus, and tympanic bones (Allin, 197 5, 1986; Allin & Hopson, 1992; Hopson, 1987, 1994; Kemp, 1982; Sloan, 1983; Carroll, 198.


Progressively, the teeth became differentiated. The large canines developed first, followed by the development of multicusped cheek teeth, reduced tooth replacement (Osborn & Crompton, 1973; Crompton & Parker, 197, and finally full y differentiated incisors, canines, premolars, and molars with one tooth replacement during life (Kemp, 1982; Hopson, 1994).


Many other morphologic changes are documented in the fossil record. These demonstrate the morphologic and geochronologic succession from sprawling limb posture to upright limb posture of mammals (Jenkins, 1971; Romer & Lewis, 197 3; Kemp, 1982; Carroll, 1988; Hopson, 1994). As Jenkins (1971, p. 210) stated, “In details of morphology and function, the cynodont post-cranial skeleton should be regarded as neither ‘reptilian’ nor ‘mammalian’ but as transitional between the two classes .” Other changes have been adequately summarized elsewhere (Kemp, 1982; Sloan, 1983; Carroll, 1988; Hopson, 1994). Obviously, fundamental physiologic changes must have taken place as well, many of which are not directly preserved in the fossil record, though some can be inferred from the skeletal anatomy (Findlay, 1968; Kemp, 1982; Sloan, 1983, Carroll, 1988; Hopson, 1994).


This is well documented in the fossil record by a massive volume of incontrovertible data that cannot be explained away. Such large-scale, progressive, continuous, gradual, and geochronologically successive morphologic change (Sidor & Hopson, 199 is descent with modification, and provides compelling evidence for evolution on a grand scale.

Scientific Creation

There are a variety of different forms of creationism (Scott, 1999b). In this article, I am limiting my discussion to “scientific creation” (= young earth creation; Scott, 1999b) because its proponents were instrumental in the Kansas dec ision. This is clearly indicated by the removal of the earth’s age from the new curriculum (Scott, 1999a, p. 21).


Gish (1985, p. 35) defined the “creation model” as follows: “By creation we mean the bringing into being of the basic kinds of plants and animals by the process of sudden, or fiat, creation described in the first two chapters of Gene sis. Here we find the creation by God of the plants and animals, each commanded to reproduce after its own kind using processes which were essentially instantaneous. We do not know how God created, what processes he used, for God used processes which are not now operating anywhere in the natural universe. This is why we refer to divine creation as special creation. We cannot discover by scientific investigations anything about the creative processes used by God.” “Scientific creationists” consider the earth to be approximately 6,000 to 10,000 years old (Gish, 1995, p. 4, and the creation event to have lasted six 24-hour days (Whitcomb, 1986, p. 28, 32; Gish, 1995, p. 4.


It is important to note that, “Creationists do not deny...the origin of variations within kinds, but they do deny...the evolutionary origin of basically different types of plants and animals from common ancestors” (Gish, 1995, p. 30) . Thus, the “creation model” presents a picture of all of the “kinds” created during the creation week. Since then, no new “kinds” have emerged. However, there has been diversification within each “kind” to produce, for example, the different breeds of do gs. This is the “creationist orchard” (Sarfati, 1999, p. 38, 39). This “variation within kinds” results from each of the “kinds” being created with a range of genetic material.


Because all the major “kinds” of organisms were created during the initial creation event, “...the organisms represented in the fossil record would all have been living contemporaneously, rather than scattered in separate time-frames over hundreds of millions of years...The only reason to think that all should not have been living contemporaneously in the past is the assumption of evolution. Apart from this premise, there is no reason to doubt that man lived at the same time as the d inosaurs and trilobites” (Morris, 1985, p. 112). The “kinds” of organisms presumably lived in different ecologic zones just as they do today (Morris, 1985, p. 118, 119). Consequently, “creation scientists” propose an alternative model to uniformitarian historical geology, in whic h a world-wide “great flood” formed the rock record, especially the fossiliferous Phanerozoic sediments (Whitcomb & Morris, 1961, p. 258, 265, 327; Morris, 1985, p. 117, 118, 123, 129; Gish, 1995, p. 49; Brown, 1996, p. 84-86). During the “great flood,” organisms were hydrodynamically sorted according to size and shape (Morris, 1985, p. 118, 119), and the ecologic zone they lived in.


In synthesis, the “creation model” includes a number of critical tenets that are drastically different from evolution, geology, biology, and paleontology: 1) gaps between created kinds, i.e., no transitional fossils; 2) “great flood;” 3) instantaneous creation and contemporaneity of faunas; and 4) young age of earth. The following sections review these tenets.
Missing Links

“Missing links” are probably the most widely known argument against evolution. “Creation scientists” claim that transitional fossils do not exist and that systematic gaps between taxa (especially higher taxa) are ubiquitous in the fossi l record (Morris, 1985, p. 78, 79; Morris & Parker, 1987, p. 11, 12; Gish, 1995, p. 80, 81, 100-103, 109, 186, 187). Concerning the lack of transitional fossils connecting ichthyosaurs with other reptiles, Gish (1995, p. 109) stated, “What we have is undoubted proof of special creation, if ever such proof is possible.” It is certainly true that transitional forms have not been found to bridge the gap between some taxa. Transitional fossils connecting the ichthyosaurs or pterosaurs with other reptiles, or the bats with other mammals are not known (Carroll, 1988, p. 251-254, 331-337, 463, 464). However, this is absence of data, and the absence of data by itself is ambiguous. It is certainly not proof of anything. That is a serious logical fallacy and a fatal flaw in “creation science” arguments against evolution. What is relevant is that are many other transitional fossils, which corroborate evolution but contradict “creation science.”


The absence of data can be interpreted in a number of different ways. First, some transitional forms may have been soft-bodied organisms that were never fossilized. A few exceptional fossil deposits (such as the Burgess Shale; Dott & amp; Prothero, 1994, p. 216-219) demonstrate that significant numbers of soft-bodied organisms lived with skeletal organisms, but that for the most part they are not preserved. Second, transitional forms may not have been preserved because of geographic a ccidents: some organisms lived in actively eroding, instead of depositing areas, or they were destroyed in an orogeny (or major erosional event). Third, transitional forms may not have been found yet. As discussed earlier, prior to the early 1980’s no tra nsitional forms were known to connect whales with their most closely related fossil relatives, the mesonychids. Since then, an impressive succession of intermediate forms has been found clearly documenting their evolution. Science progresses by finding ne w data. Fourth, transitional forms may have existed for such a short duration of geologic time that they were not preserved, resulting in evolution by punctuated equilibrium. Fifth, transitional forms may have lived elsewhere and the organisms subsequentl y migrated to other locales. In the upper Upper Cretaceous (Campanian and Maastrichtian) of North America, we find abundant ceratopsian dinosaurs with no obvious local ancestors (Carroll, 1988, p. 309-311). However, in eastern Asia, we find two forms in t he upper Lower and lower Upper Cretaceous, Psittacosaurus and Protoceratops, which bridge the gap between generalized bipedal ornithopods and classical quadrupedal ceratopsians (Carroll, 1988, p. 309-311; Norman, 1998, p. 128-133). Apparentl y, the protoceratopsians migrated to North America during the middle of the Upper Cretaceous and an adaptive radiation ensued resulting in a plethora of genera, including the most famous, Triceratops (Edwords, 1982; Carroll, 1988, p. 309-311).


Critique of the Fossil Evidence


Not only do “creation scientists” misinterpret the ambiguity of missing links, they also do not accept the evidence for transitional fossils that does exist. An instructive lesson is a careful examination of their arguments against the evolution of mammals from synapsid reptiles (Gish, 1995). First, concerning amphibians, reptiles, and mammals, Morris (1985, p. 83) stated, “All of them are four-legged vertebrates with similar skeletal s tructures and thus their fossilized remains provide little basis for distinguishing between them.” That statement is partially incorrect; there are, in fact, many skeletal features which distinguish these classes (Carroll, 198.


Second, as is typical of “creation science” books, Gish (1995) presented a series of quotes that have been taken out of context from various articles about synapsid evolution and fitted together to form a story that misrepresents the meaning of the original authors’ works. That is not corroborative evidence for “creation science,” and it does not disprove evolution.


Third, Gish (1995, p. 149) claimed that, “In their attempts to establish an evolutionary tree or phylogeny for the mammal-like reptiles and the mammals, evolutionists rely almost entirely on similarities to link these creatures in an evolutionary scenario. They are forced to do this because of the lack of transitional forms required for their hypothetical evolutionary ladder.” Further, Gish claimed that large and systematic gaps separate the major groups of synapsids from each other and from mammals (Gish, 1995, p. 151, 159-163). Gish (1995, p. 161) claimed, “The fossilized remains of each of these stages appear fully-formed, with no transitional forms documenting the gradual transition of one stage into the next, and very little, if any, further change occurs until this stage or level is abruptly replaced by the next.” All of these claims are directly contradicted by fossil evidence. Virtually none of the groups appear fully formed nor exhibit very little internal evolution. Within the sphenacodonts, from the Upper Pennsylvanian to Lower Permian, the angular notch is noticeably deepened and the reflected lamina became a noticeable flange (Currie, 1977, 1979; Romer & Price, 1940; Hopson, 1994). Within the cynodonts, significant e volution took place. The oldest cynodonts from the upper Upper Permian have an incomplete bony secondary palate (Parrington & Westoll, 1940; Hopson, 1987, 1994; Kemp, 1979). Subsequently, in Triassic cynodonts, the palate was completed. The bony palat e was progressively formed and sutured, not instantly formed (Parrington & Westoll, 1940; Parrington, 1946; Hopson, 1987, 1994; Fourie, 1974; Romer, 1969b, 1970b, 1973; Carroll, 198. Also, the reflected lamina was progressively and gradually transfo rmed into a tiny horseshoe-shaped bone (Allin, 1975; Allin & Hopson, 1992; Hopson, 1987, 1994; Brink, 1963; Kemp, 1979; Fourie, 1974; Romer, 1969b, 1970b, 1973; Carroll, 198.


Fourth, Gish (1995, p. 164) stated that, “It is apparent that the argument for linking pelycosaurs to the therapsids is extremely weak and is based solely on certain similarities. There are no transitional forms that would provide ac tual evolutionary links between pelycosaurs and therapsids.” Here Gish quoted Romer & Price (1940) out of context and altered the meaning of their conclusions. In fact, the fossil evidence contradicts Gish’s claim: the oldest therapsids and sphenacodo nts are very similar in nearly every aspect of their morphology, especially the skulls (Romer & Price, 1940; Currie, 1977, 1979; Tchudinov, 1960, 1983; Efremov, 1954; Olson, 1962; Sigogneau & Tchudinov, 1972). This was demonstrated 90 years ago (B room, 1910)!


Fifth, Gish (1995, p. 165) stated that, “It must be emphasized that the non-cynodont therapsids appeared abruptly, that is, with all their basic characteristics complete ...There are no transitional forms, no intermediates, that link these...to some hypothetical pelycosaur ancestor.” That statement is contradicted by the fossil record. The therapsids do not appear fully formed; the oldest are more similar to the pelycosaurs than to the cynodonts in their morphology (Romer & Price , 1940; Currie, 1977, 1979; Tchudinov, 1960, 1983; Efremov, 1954; Olson, 1962; Sigogneau & Tchudinov, 1972). The eotitanosuchians are in fact intermediates, as is clearly indicated by the enlargement of the lateral temporal fenestra and reflected lami na compared with the pelycosaurs but not to the degree of the other younger therapsids, including the therocephalians. Moreover, the eotitanosuchians do not have a coronoid process (like the pelycosaurs) but do have well developed canines (like subsequent therapsids; Romer & Price, 1940; Currie, 1977, 1979; Tchudinov, 1960, 1983; Efremov, 1954; Olson, 1962; Sigogneau & Tchudinov, 1972).


Sixth, Gish (1995, p. 166) stated that, “the cynodonts...are found at the earliest levels in rocks of the Late Permian.” That is incorrect; the oldest cynodonts are in fact from the late part of the Late Permian (Kemp, 1979, 1982).


Seventh, concerning Morganucodon, Gish (1995, p. 169) stated, “What is the evidence for a squamosal-dentary joint in these creatures? This evidence consists of an alleged condyle on the dentary.” That statement misrepresents t he data. The condyle is definitely present; it is not “alleged” (Kermack, Mussett, & Rigney, 1973, 1981; Carroll, 198. The corresponding shallow depression in the squamosal into which the condyle fitted in life corroborates this. Hopson (1987) state d that articulated material has been found with the two bones in contact.


Eighth, Gish (1995, p. 169, 170) stated that, “The anatomy required for (the reptilian jaw-joint), including the arrangement and mode of attachment of musculature, the arrangement and location of blood vessels and nerves, etc., must be quite different from that required for a mammalian jaw-joint. How then could a powerful, fully functional reptilian jaw-joint be accommodated along with a mammalian jaw-joint?” That statement is irrelevant because fossils of Morganucodon conclus ively demonstrate that the two jaw joints did exist side-by-side (Kermack, Mussett, & Rigney, 1973, 1981; Carroll, 198. That is incontrovertible evidence that cannot be explained away. Moreover, the new mammalian jaw musculature developed progressiv ely throughout the cynodonts, beginning with the Upper Permian procynosuchids (Barghusen, 1968; Crompton, 1972; Crompton & Parker, 1978; Hopson, 1987, 1994). The new muscles progressively expanded onto more and more of the coronoid process and posteri or part of the dentary (Barghusen, 1968; Crompton, 1972; Crompton & Parker, 1978; Hopson, 1987, 1994). Thus, the mammalian jaw musculature evolved while the lower jaw was still hinged to the skull only by a reptilian jaw joint, and was already present in Morganucodon .


Ninth, Gish (1995, p. 171) stated that, “Finally, and this is conclusive, not a single intermediate between an animal with a powerful, fully functional reptilian jaw-joint and a powerful, fully functional mammalian jaw-joint has been found.” That statement is incorrect. Morganucodon contains both jaw joints side-by-side (Kermack, Mussett, & Rigney, 1973, 1981; Carroll, 198. Tenth, concerning the evolution of the middle ear, Gish (1995, p. 167, 16 stated that, “Another difficulty with the above notion is the fact that while thousands of fossils have been found which possess a single ear bone and multiple jaw bones, and thou sands of fossil mammals have been found which possess three ear bones and a single bone in the jaw, not a single fossil creature has ever been found which represents an intermediate stage, such as one possessing three bones in the jaw and two bones in the ear.” That misrepresents how the mammalian middle ear evolved. As demonstrated by the fossil record, the quadrate and articular became part of the middle ear as a unit, along with the angular (Allin, 1975, 1986; Allin & Hopson, 1992; Hopson, 1966, 1987, 1994; Ro sowski, 1992; Crompton, 1972; Crompton & Parker, 197. Gish (1995, p. 171) continued by stating, “This would have required that the stapes (columella) of the reptile become free from its attachment to the tympanum (ear drum), and the retroarticular p rocess of the articular gain an attachment to the tympanum...Somehow, while all of this was going on, the quadrate bone of the reptilian ancestor must gain its freedom, move into the middle ear, and insert itself between the stapes and malleus...” That is false.

First, in the oldest reptiles, including synapsids, the stapes extended from the inner ear to the quadrate; a lizard-like tympanum was never present (Carroll, 1964, 1988; Romer & Price, 1940; Allin, 1975, 1986; Allin & Hopson, 1992).
Second, in therapsids, especially cynodonts, the tympanum was suspended across the angular cleft supported in part by the reflected lamina and the other post-dentary bones including the articular (Allin, 1975; Allin & Hopson, 1992).
Third, the retroarticular process of the articular already had contact with the tympanum (Allin, 1975; Allin && Hopson, 1992).
Fourth, the quadrate was already present between the stapes and the articular, not necessitating any such movement (Allin, 1975; Allin & Hopson, 1992).
All of this is documented by the fossil record. Concerning his version of origin of the mammalian middle ear, Gish (1995, p. 171) stated, “There is absolutely no fossil evidence whatsoever to support such an incredible scenario.” That’s because his versi on of the origin of the mammalian middle ear is wrong.


Eleventh, continuing about the soft part anatomy of the mammalian inner ear, Gish (1995, p. 172) stated that, “The organ of Corti...has no homologue in reptiles. There is no possible structure in the reptile from which it could have been derived. It would have had to have been created de novo, since it was entirely new and novel.” That statement is incorrect. In fact, the basilar papilla of the reptilian inner ear is homologous with the organ of Corti (Romer, 1956, p. 33-38, 1970a; S loan, 1983). The basilar papilla, or organ of Corti, is contained in one portion of the inner ear known as the cochlear canal (Romer, 1956, p. 33-38, 1970a; Allin & Hopson, 1992). The cochlear canal is encased in bone and endocasts can be made that deline ate its shape (Allin & Hopson, 1992). In cynodonts, the cochlear canal is a short blunt feature (Allin & Hopson, 1992). In Morganucodon, it is elongate and slightly curved (Allin & Hopson, 1992). In modern mammals it is long and coiled (Allin & Hopson, 1992). Indeed, even the inner ear did not appear fully formed but progressively evolved.


Twelfth, Gish (1995, p. 152) stated that the succession of synapsid taxa “...must be juxtaposed according to an imagined evolutionary sequence, or at least according to some scheme determined by assumptions based on indirect evidence .” That is incorrect. In fact, the evidence for the geochronologic order of the various synapsid-bearing strata is quite good and independent of any evolutionary assumptions (Kemp, 1982; Frenzel, et al., 1988; Jones & Hentz, 1988; Olson, 1957, 1962; Tchudinov 1965; Efremov & Vyushkov, 1955; DuToit, 1954; Keyser & Smith, 1977-78; Bonaparte, 1966; Romer, 1966; Romer & Jensen, 1966; Waterhouse, 1978; Ross, 1979; Harland et al., 1989). In conclusion, everything that is known abou t the fossil record of synapsid reptiles and early mammals contradicts not only the basic predictions of the “creation science” model, but also contradicts point-by-point most of the detailed discussion of the topic by Gish (1995). The same conclusion can be said for “creationist scientists’” interpretations of the remainder of the fossil record (Gish, 1978, 1985, 1995). One paleontologist’s critique of Gish (197 is: “On 67 of the 97 text pages I found at least one error of fact, logical error, or quota tion out of context, all chosen carefully to mislead the reader. On checking a standard college logic text with a list of logical fallacies, I found that Gish did not manage to miss a single one! Their works have the appearance of scholarship, but not the substance” (Sloan, 1983, p. 263).

Created Kinds

“Scientific creationists” classify organisms not by standard Linnean taxonomic procedures, but rather group them into basic “kinds” (the terms “type” and “kind” are apparently synonymous; Gish, 1995, p. 29-31). As Morris & Parker (1987, p. 137, 13 stated, “For creationists, it’s the created type that is the real unit in nature.” Gish’s (1995, p. 29) definition is that, “A basic animal or plant type would include all animals or plants which were truly derived from a single stock.” As e xamples of “basic kinds,” Gish (1995, p. 30) offered the following: “Among the vertebrates, the fishes, amphibians, reptiles, birds, and mammals are obviously different basic types. Among the reptiles, the turtles, crocodiles, dinosaurs, pterosaurs..., an d ichthyosaurs...would be placed in different kinds. Each one of these major groups of reptiles could be further subdivided into the basic kinds within each. Within the mammalian class, duckbilled platypuses, opossums, bats, hedgehogs, rats, rabbits, dogs , cats, lemurs, monkeys, apes, and men are easily assignable to different basic types. Among the apes, the gibbons, orangutans, chimpanzees, and gorillas would each be included in a different basic kind.”


That is curious: “kinds” are identified to exist as a hierarchy, “kinds” within other “kinds.” Yet Gish (1985, p. 34; 1995, p. 35) stated both that God separately created all of these basic animal and plant “kinds,” and that a “kind” includes those variants which have been derived by genetic variation from a single stock. If a “kind” consists of all those variants derived from a single stock, then how can some of the variants also have been created separately? At what level did God r eally create? This is both internally inconsistent and a major logical fallacy. Furthermore, it renders “creation science” neither falsifiable nor scientific. Scientists, and to some extent “creation scientists,” both agree that finding transitional forms between taxa (or “kinds”) would falsify “scientific creationism” (Cuffey, 1984; Gish, 1995, p. 40, 41). But, given the internally inconsistent definition of “basic kind,” what should be looked for? If intermediates between two species of the brachiopod < i>Eocoelia are found, it can be explained as “variation within the Eocoelia kind.” If intermediates connecting Hyracotherium with Equus are found, it can be explained as “variation within the horse kind.” If intermediates between mesonychid ungulates and whales are found, it can be explained as “variation within the mammal kind.” If intermediates between reptiles and mammals are found, it can be explained as “variation within the vertebrate kind.” One could also argue that such in termediates are separate “created kinds.” For example, Morris & Parker (1987, p. 137) stated that, “Because of its unique combination of complete, functionally integrated traits, Archaeopteryx would qualify as a created type.” That is an illogi cal semantic game that renders “creation science” unscientific.


“Scientific creationists” equate “variation within a kind” with microevolution and origin of new “kinds” with macroevolution (Brown, 1986; Morris, 1994). That misrepresents both concepts. As previously stated, microevolution results in the origin of new species. As defined by Gish, some “kinds” are species (such as humans; Gish, 1995, p. 29) and so their origin would be by microevolution, not macroevolution, and thus could be considered “variation within a kind.” That internal incons istency thus implies that humans originated by microevolution and were not specially created. Furthermore, some “kinds” as defined by Gish include not just many species, but also more than one higher taxon, and so their origins include both macroevolution and microevolution.

Faunal Succession and Correlation

“Scientific creationists” reject faunal succession and the geologic time scale (Whitcomb & Morris, 1961; Morris, 1985; Bliss, 1988; Gish, 1995). That is an attempt to discredit evolution. If one can show that superposition, faunal s uccession, biostratigraphy, correlation, and the geologic time scale are invalid, then the geochronological successions of transitional fossils would be rendered invalid. Thus, “creation scientists” propose that the successive appearance of taxa in the fo ssil record is the result of ecologic zonation (Morris & Parker, 1987, p. 163-165), mobility of vertebrates (Whitcomb & Morris, 1961, p. 275-277; 279-286), and hydrodynamic (Whitcomb & Morris, 1961 p. 273, 274; Morris, 1985) or liquefaction so rting (Brown, 1996) during the “great flood.” Significant evidence (e.g., C. Cuffey, 1999) indicates that the rock record is definitely not the result of a “great flood,” and therefore any hypothesis about the origin of faunal succession involving the “great flood” is also false and irrelevant.


“Scientific creationists” assert that relative age dating of rocks uses circular reasoning based on the assumption of evolution (Whitcomb & Morris, 1961, p. 134, 136, 203, 205; Morris, 1978; Morris, 1985, p. 94-96, 134-137, 229, 232; Morris & Parker, 1987, p. 239-242; Bliss, 1988, p. 36). For example, Morris (1985, p. 136) stated, “Here is obviously a powerful system of circular reasoning. Fossils are used as the only key for placing rocks in chronological order. The criterio n for assigning fossils to specific places in that chronology is the assumed evolutionary progression of life; the assumed evolutionary progression is based on the fossil record so constructed. The main evidence for evolution is the assumption of evolutio n!”


That is false. Rocks are placed in proper chronological order by superposition (Van de Fliert, 1968; Dott & Prothero, 1994, p. 16-41, 73-91). Therefore, the succession of rock layers accurately represents the history of the earth . Thus, the fossil record contained within accurately represents the history of life on earth. If we collect fossils from stratigraphic sections where superpositional relationships can be easily determined solely on physical criteria, we find that there i s a definable succession of fossil taxa, each occurring in a limited stratigraphic interval. This pattern is an empirical observation that is both verifiable and repeatable. Within a local area, where the correlations between stratigraphic sections can be determined on physical criteria (geologic mapping, well log correlation), we find very similar successions of taxa at each of the sections (Lochman-Balk, 1971; Palmer, 1971; Key, 1990; Stitt, 1971, 1977). Such physical correlations are spectacularly illustrated in the Lower Ordovician of the Arbuckle Mountains of south-central Oklahoma and the Upper Pennsylvanian and Lower Permian of north-central Oklahoma and east-central Kansas, where one can literally walk out lithostratigraphic units for miles across the prairies. If we expand our area of investigation, we fin d that the same succession of fossils repeatedly occurs elsewhere. It can be demonstrated by regional geologic mapping and subsurface correlation that the rock layers containing each specific assemblage of fossils are physically correlative. This is spect acularly illustrated on the Colorado Plateau, where one can clearly trace the rock units by physical correlation.


This is the principle of faunal succession. It does not rely on untestable evolutionary assumptions. Faunal succession was first demonstrated by Smith in England, and by Cuvier and Brogniart in France, in the late 1700s and earliest 1800s (Dott & Prothero, 1994 p. 23-25). Evolution was not assumed; in fact, Cuvier believed that all life was created early, and d’Orbigny believed that different faunas were repeatedly created and wiped out by God (Dott & Prothero, 1994, p. 25, 2 6). Such observations preceded Darwin’s Origin of Species by more than 50 years.


Faunal succession can be readily applied in our own experiences. While growing up and attending college in Pennsylvania and Ohio, I collected fossils from all over the western Appalachian Valley and Ridge, the Appalachian Plateau, th e Great Lakes region, and the Ohio River valley. Throughout this region, rocks containing the trilobite Cryptolithus (Shimer & Shrock, 1944; Hoskins, 1969; Feldmann & Hackathorn, 1996) are always overlain by rocks with the brachiopods St egerhynchus, Whitfieldella, and Eospirifer, and halysitid corals (Shimer & Shrock, 1944; Hoskins, 1969; Feldmann & Hackathorn, 1996); which are always overlain by rocks with the brachiopods Paraspirifer and Mucrospirife r and the trilobite Phacops (Shimer & Shrock, 1944; Kesling & Chilman, 1975; Hoskins, 1969; Feldmann & Hackathorn, 1996); which are always overlain by rocks containing the bryozoan Archimedes and the blastoid Pentremites (Shimer & Shrock, 1944; Galloway & Kaska, 1957; McKinney, 1999). This succession is invariant; I have never observed Archimedes stratigraphically below, nor with, Cryptolithus, for example. This succession can be independently dem onstrated by physical stratigraphy to be in the same superpositional order. Based on local and regional scale geologic mapping, and subsurface correlation, the rock intervals from different regions and containing the same fauna can be demonstrated to be p hysically correlative. These genera are not in a specific evolutionary ancestor-descendant relationship and so the succession is definable without any underlying assumption of evolution. Faunal succession is an empirical observation, not an evolutionary a ssumption.


At a more detailed level, the development of Ordovician graptolite biostratigraphy in North America provides a good case study of biostratigraphic methods based on faunal succession (Berry, 1977), and one that is independently testab le (Goldman et al., 1994; Mitchell et al., 1994). Fifteen graptolite biozones have been recognized, defined, and refined by nearly a century of detailed work. Based on superpositional order, the same succession of graptolite species and zone s is recognized in New York (Ruedemann, 1904, 1908, 1912, 1925, 1947; Berry, 1962, 1963, 1970; Mitchell et al., 1994; Goldman et al., 1994), Quebec (Riva, 1969, 1974), Newfoundland (Kindle & Whittington, 1958; Whittington & Kindle, 1 963), west Texas (King, 1937; Berry, 1960; Bergstrom, 197, Yukon (Jackson, 1964; Jackson & Lenz, 1962), and east-central Alaska (Churkin & Brabb, 1965). Moreover, isolated localities with only short stratigraphic sections can be compared with po rtions of the zonation defined elsewhere (Ross & Berry, 1963). No assumption of evolution was made. The fact that this same succession occurs repeatedly in different regions all over North America, and that the succession can be independently verified by anyone willing to recollect the localities, leads to the conclusion that geochronologic correlation based on biostratigraphy is valid.


This conclusion can be independently tested. The Middle Ordovician Trenton Group and Utica Formation of New York contain three of the graptolite zones and also contain numerous K-bentonite beds (Goldman et al., 1994; Mitchell et al., 1994). Because the K-bentonite beds are volcanic ash-falls, they represent geologically instantaneous isochrons. Furthermore, trace element geochemistry of their contained volcanic glass distinguishes each K-bentonite bed, assures proper co rrelation, and establishes a geochronologic framework to which the graptolite zones can be compared (Goldman et al., 1994; Mitchell et al., 1994). Indeed, the graptolite zone boundaries are parallel with the K-bentonite beds, therefore indep endently corroborating graptolite zones as time-parallel (Goldman et al., 1994; Mitchell et al., 1994). This independently demonstrates the validity of biostratigraphy on a local scale, and corroborates its use as a method of geochronologic correlation.


Based upon similar detailed biostratigraphic correlations, augmented with physical stratigraphic correlations, mapping, and subsurface correlations, it has long been thought that the Decorah (Minnesota), Spechts Ferry (Iowa, Wisconsi n, Illinois), Tyrone (Kentucky), Eggleston (Virginia), and Carters (Tennessee) formations, and the Chickamauga/Stones River/Nashville (Alabama, Georgia) groups throughout the eastern United States are correlative with each other. These formations each con tain a pair of thick bentonite beds (Deicke and Millbrig bentonites), within the upper part of the Phragmodus undatus conodont zone (Huff & Kolata, 1990). Geochemical fingerprinting with rare earth elements independently demonstrates that in ea ch locale, it is the same pair of bentonite beds. This independently demonstrates both that these formations are correlative and the validity of biostratigraphy on a local and regional scale (Huff, 1983; Kolata, Frost, & Huff, 1987; Huff & Kolata, 1990; Kolata, Huff, & Bergstrom, 1996). Moreover, biostratigraphic studies indicated that these formations were equivalent to the middle Caradocian of Estonia. There, the Big Bentonite is found at the base of the Keila Formation (Huff, Bergstrom, &am p; Kolata, 1992). Both the Millbrig and the Big Bentonite contain the same phenocryst composition, geochemical fingerprint, and Ar-Ar radiometric age (Huff, Bergstrom, & Kolata, 1992). This independently demonstrates the validity of biostratigraphy on a world-wide scale. Similar independent tests have been done on Cretaceous biozones (Wise, 1998, p. 165) and Cenozoic biozones (Evernden et al., 1964). In both cases, the biostratigraphic framework was found to be consistent with radiometric ages.


Morris (1985, p. 95) quoted Evernden et al. (1964), as stating “Vertebrate paleontologists have relied upon ‘stage of evolution’ as the criterion for determining the chronologic relationships of faunas.” That appears to cast d oubt on the validity of the succession of Cenozoic land mammal faunas from western North America. That quote is, however, taken out of context and consequently misrepresents the conclusions of Evernden et al. (1964). In fact, the very next sentence in Evernden et al. (1964, p. 166), states that, “The physical dates presented in this paper demonstrate that temporal position of genera and species of fossil mammals in their accepted phylogenies is accurate at Mammal-Age degree of refinement.” Moreover, the overall conclusion of Evernden et al. (1964, p. 145), was that, “The K/A ages and the Mammal Age designations are in essentially perfect agreement, thus substantiating the usefulness of the K/A techni que throughout the Tertiary and supporting the conclusion that the defined Mammal Ages have true evolutionary significance. Correlations with European ages and Pacific Coast foraminiferal Ages through both K/A and fossil criteria are internally consistent .” And furthermore, “The correspondence of the two sets of data discussed in this paper is so close as to leave little doubt that the defined Land-Mammal Ages are time-sequential.”


Faunal succession directly contradicts the predictions of “creation science.” All taxa, including higher taxa from genera to phyla, do not appear simultaneously in the fossil record. The oldest occurrences of the animal phyla and cl asses range from the uppermost Precambrian (Phylum Cnidaria) through the Upper Jurassic (Class Aves; Benton, 1993). Likewise, the oldest occurrences of the classes of vascular land plants range from the Middle Silurian (possibly Upper Ordovician) through the Lower Cretaceous (Stewart, 1981). Furthermore, all taxa did not live contemporaneously as in a post-creation, pre-flood world. This is true not only if we examine species, but also higher taxa, from genera to phyla (Benton, 1993). Of special note here is the "Cambrian explosion." "Creation scientists" imply that the major taxa of invertebrates appeared suddenly, essentially contemporaneously, and fully formed in the Cambrian (Gish, 1995, p. 54-69, 75; Morris, 1985, p. 80, 81; Morr is & Parker, 1987, p. 126-129). That is incorrect. In fact, the oldest occurrences of the major taxa of invertebrates range from the uppermost Precambrian through the Upper Ordovician (Boardman, Cheetham, & Rowell, 1986; Taylor & Larwood, 19 90; Benton, 1993; Gehling, 1986; McMenamin, 1987; Ausich, 1997; Ausich & Babcock, 199. Even considering just those major taxa that first occur in the Lower Cambrian, the first occurrences are still successive within the Lower Cambrian, not simultan eous (Narbonne et al., 1987; Smith, 1990; Signor & Lipps, 1992; Mount & Signor, 1992; Rozanov & Zhuravlev, 1992; Jiang, 1992; Briggs & Fortety, 1992; Popov, 1992; Debrenne, 1992; Crimes, 1992; Sprinkle, 1992; Landing, 1988, 1989, 19 92, 1994; Landing et al., 1989; Bowring et al., 1993; Isachsen et al., 1994). Moreover, the organization of at least some ecologic communities slowly developed throughout the Cambrian and Ordovician (Ausich & Bottjer, 1982, 1990; Bottjer & Ausich, 1986). When one examines Cambrian and Ordovician rocks, it is readily apparent that a typical, diverse "Paleozoic fauna," dominated by brachiopods, bryozoans, and crinoids, first occurs in Middle Ordovician rocks. Morris & Parker (1987, p. 127) and Bliss (1988, p. 39) presented a diagram of life on a Cambrian seafloor, including sea urchins and starfish. That is incorrect. The oldest starfish are Lower Ordovician (Benton, 1993, p.507) and the oldest sea urchins are Upper Ordovician (Benton, 1993, p.511). Bliss ( 1988, p. 41) stated, "Many complex invertebrates are found in Cambrian strata; the ones living today are similar." The second part of that statement is simply incorrect; Cambrian and modern invertebrates are easily distinguished.


Morris (1985, p. 227, 22 and Whitcomb (1986, p. 75, 76, 84), based upon their interpretations of Genesis, provided a list of predictions about the order of creation of organisms:

land plants were the first life forms created (Morris, 1985, p. 227, 228; Whitcomb, 1986, p. 75);

fruit trees before fishes (Morris, 1985, p. 227, 228; Whitcomb, 1986, p. 75);

birds before insects (Morris, 1985, p. 227, 22;

birds before reptiles (Morris, 1985, p. 227, 228; Whitcomb, 1986, p. 76);

birds contemporaneous with fishes (Whitcomb, 1986, p. 76);

insects after flowering plants (Whitcomb, 1986, p. 76); and

whales before land mammals (Whitcomb, 1986, p. 84).

Because the fossil record accurately represents the history of life, we can test these predictions.


First, the oldest land plants (mosses and vascular plants) are from the Middle Silurian (possibly the Upper Ordovician) and are definitely not the oldest fossils (which are cyanobacteria from the Archaean; Benton, 1993, p. 779, 781; Stewart, 1981; Dot t & Prothero, 1994, p. 195, 286-28.

Second, the oldest fishes (all classes of fishes) are definitely older than the oldest fruit trees (angiosperms); the oldest occurrences of the various fish classes ranges from Upper Cambrian to Lower Devonian (Benton, 1993, p. 574, 584, 589, 590, 594 , 611-613) whereas the oldest fruit trees are Lower Cretaceous (Stewart, 1981; Doyle, 1977).

Third, the oldest insects (middle Lower Devonian; Benton, 1993, p. 365) are definitely older than the oldest birds (upper Upper Jurassic; Benton, 1993, p. 717, 71.

Fourth, the oldest reptiles (either Lower Mississippian or Middle Pennsylvanian; Benton, 1993, p. 681, 683) are definitely older than the oldest birds.

Fifth, birds and fish do not appear in the fossil record at the same time; the oldest fish are older than the oldest birds.

Sixth, the oldest insects are definitely older than the oldest angiosperms (“flowering plants”); even if “flowering plants” are considered to include the cycadeoids (Upper Triassic; Stewart, 1981, p. 289), the insects are still older.

Seventh, the oldest land mammals (Upper Triassic; Kermack, Mussett, & Rigney, 1973, 1981; Benton, 1993, p. 740) are definitely older than the oldest whales (Lower Eocene; Gingerich et al., 1983). In every case, the predictions of “creation scientists” are contradicted by the fossil record. Both Morris (1985) and Whitcomb (1986) concede that the paleontological evidence does indeed contradict their predictions.

“Creation scientists” attempt to discredit faunal succession and evolution by discussing examples of “out-of-order fossils.” “Creation scientists” claim fossil human footprints, body parts, and artifacts have been found in pre-Plioce ne rocks (Helfinstine & Roth, 1994; Baugh & Wilson, 1987, 1992; Brown, 1996, p. 22, 23, 43, 61, 62). A thorough discussion of each is beyond the scope of this article. In every case that I was able to check, these remains are demonstrably not huma n, but instead either dinosaur footprints (Weber, 1981; Cole et al., 1985; Hastings, 1985; Godfrey, 1981, 1985; Kuban, 1986), fish teeth (Hastings, 1995), inorganic rock features (Conrad, 1981), or hoaxes (Lippard, 1989; Weber, 1981; Godfrey, 1985) . Moreover, some of the artifacts are obviously modern tools dropped or buried in ancient sediment or rock (Lippard, 1989; Cole, 1985). There is no credible evidence of humans living prior to the Pliocene. Instead, there is abundant evidence indicating ho minids evolved during the Pliocene (Johansen & Edgar, 1996; Lewin, 1993).


“Creation scientists” claim that Precambrian rocks overlying Cretaceous rocks (by thrust faulting) in Glacier National Park of western Montana render superposition and faunal succession unreliable (Whitcomb & Morris, 1961, p. 180 -200). They stated “...we feel warranted in rejecting the whole concept of over-thrusting, at least when applied on the scale of the so-called Lewis and Hart Mountain Thrusts...” That is incorrect. Thrust faults, including the Lewis Overthrust, can be ide ntified by geologic mapping and other physical criteria (Van de Fliert, 1968; Allmendinger, 1992).


Bliss (1988, p. 49) stated that Eohippus (=Hyracotherium) has been found with Equus in surface strata, thereby discrediting the evolution of horses. No references are given, no localities are given, no museum specimen numbers are given, no illustrations are given, and no precise stratigraphic information is given (the term surface strata is ambiguous; does he mean soil or any of the Phanerozoic rock formations cropping out at th e surface?). Thus his claim is not credible. According to Simpson (1951) and MacFadden (1992), Hyracotherium is not found in the same strata with Equus. Gish (1992, p. 36) stated that, “The most recent fossil of an armored dinosaur (buried i n the ice in Antarctica), was found in 1988 by an expedition to the South Pole.” This statement is false; dinosaurs have been found in Cretaceous sedimentary rocks in Antarctica, but not ice (Wise, 1998, p. 171).




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« Reply #4 on: September 15, 2005, 07:29:23 AM »

Silly, Hunter. Everybody knows that heaven and earth were once joined as Ranginui, the Sky Father, and Papatuanuku, the Earth Mother, lay together in a tight embrace. They had many children who lived in the darkness between them. The children wished to live in the light and so separated their unwilling parents. Ranginui and Papatuanuku continue to grieve for each other to this day. Rangi's tears fall as rain towards Papatuanuku to show how much he loves her. When mist rises from the forests, these are Papa's sighs as the warmth of her body yearns for him and continues to nurture mankind.



EDIT: I seriously don't have time to read it all, but in skimming it, I found a problem with the section on "transitional" fossils. The problem with the entire idea of "transitional" fossils in the record is:

1) "transitional" is not clearly defined
2) evolution does not predict a "transitional" fossil record
3) it entails an oversimplification of both evolution and geology

This isn't so much a problem with your paper, but a problem with the idea of "transitional" fossils, which comes up so often in this sort of debate.
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The English language doesn't steal words from other languages; it ambushes them in dark alleys and rifles through their pockets for loose grammar.
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« Reply #5 on: September 15, 2005, 09:42:09 AM »

Wrong, the Flying Spaghetti Monster is the only true divinity.
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