Reptile to Mammal transition

Discussion in 'Creation vs. Evolution' started by Administrator2, Jan 11, 2002.

  1. Administrator2

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    QXR37
    The mammal-like reptiles were a group of animals that lived in the Permian and Triassic periods, and they provide some of the nicest examples of "transitional fossils" in the fossil record. Although soft body parts like fur and mammary glands are not preserved, there are a great many skeletal features which clearly differentiate reptiles from mammals, and we can see almost all of these gradually developing in the mammal-like reptiles. For example, reptiles walk with their legs sprawled out sideways, while mammals carry their legs straight under their bodies, and the fossil record shows a sequence of species with increasingly mammalian gaits. Also, reptile's teeth all look basically the same, while mammalian teeth are differentiated into bicuspids, incisors, and canines; again, in the mammal-like reptiles we see the teeth becoming gradually more specialized into the mammalian form. And while a reptile's jaw is made up of several bones (dentary, splenial, angular, surangular, prearticular) the mammal's jaw is made of only one, the dentary, with several of the other bones having shrunken enormously and become part of the mechanism of the inner ear. Again, the fossil record shows a sequence of mammal-like reptiles in which the dentary is gradually crowding out the other bones, finally leading to a mammal-like jaw. These are just a few of the most important reptile/mammal differences--there are many others, and in virtually every case you can see a gradual transition from a reptile-like structure to a mammal-like structure.

    Here are some sites I found on the reptile/mammal transition, many with nice pictures:
    A site about "early mammal-like reptiles": http://www.museums.org.za/sam/resource/palaeo/cluver/early.htm

    And the sequel, "later mammal-like reptiles": http://www.museums.org.za/sam/resource/palaeo/cluver/later.htm

    "Evolution: From Reptiles to Mammals": http://genesispanthesis.tripod.com/fossils/rept_mam.html

    A site addressing some creationist critiques of the reptile/mammal evidence: http://www.geocities.com/osarsif/ce06.htm

    A site listing the various kinds of therapsids (an 'advanced' group mammal-like reptile, or alternately a group of'primitive' mammals): http://home.houston.rr.com/vnotes/unit10.5.html

    A site about "transitional fossils" which has a section on the reptile/mammal transition, including some niceimages—definitely worth checking out: http://asa.calvin.edu/ASA/resources/Miller.html

    And here's a brief summary of the skeletal features distinguishing reptiles from mammals, and the evidence of a gradual transition, from this site: http://www.cmnh.org/fun/dinosaur-archive/1994Jul/0032.html

    What specific details determine that a fossil is from a reptilian mammal?
    I think you mean what makes a mammal-like reptile? However here is a sample of *some* of the characters and *some* of the forms which make up the therapsis -> mammal transition .

    1 Reptiles: Single occipital condyle
    Mammals: Double occipital condyle

    2 Reptiles: Undifferentiated dentition
    Mammals: Differentiated dentition

    3 Reptiles: No secondary palate
    Mammals: secondary palate

    4 Reptiles: No diaphram
    Mammals: Diaphram

    5 Reptiles: Uncrowned, uncuspate teeth
    Mammals: Crowned, cuspate teeth

    6 Reptiles: Teeth with single root
    Mammals: Teeth with multiple roots

    7 Reptiles: Lower jaw of several bones
    Mammals: lower jaw of dentary bone only

    8 Reptiles: Jaw joint quadrate-articular
    Mammals: Jaw joint dentary-squamosal

    9 Reptiles: Lumbar region with ribs
    Mammals: Lumbar region free

    10 Reptiles: Separate clavical ribs
    Mammals: Fused clavical ribs

    11 Reptiles: Flat scapular
    Mammals: Strong spine on scapular

    12 Reptiles: Pelvic elements separate
    Mammals: Pelvic elements fused

    13 Reptiles: Limbs out from body
    Mammals: Limbs under body

    14 Reptiles: Cold blooded
    Mammals: Warm blooded

    15 Reptiles: Scales
    Mammals: Fur/hair

    16 Reptiles: Joined external nares
    Mammals: Separate external nares

    The reptiles evolved into four major groups; the anapsids, which produced the turtles, the diapsids which produced the dinosaurs, and an offshoot group, the eurapsids, which produced the icthyosaurs. The final group, the synapsids, took a radically different path than the other groups and produced the therapsids, which concentrated on osteo- and pysiological changes which eventually produced the mammals. The group called the cynodontia (dog tooth) produced a lineage of forms intermediate between reptiles and mammals.

    [The following is not a direct lineage, but representatives of successful, related groups which exhibit a gradual aquisition of mammalian characters during the Permian-Triassic.

    The group looks like this:

    A B C D E F G
    | | | | \/ |
    …… Cynodont ----------------------------------------> Mammal


    A
    Procynosuchus_, Latest Permian-Triassic, South Africa

    Has an expanded temporal region; large zygomatic arch; enlarged dentary, but the lower jaw is still made up of several bones (albeit reduced); the begining of a secondary palate; double occipital condyle (first major mammalian character).

    B
    Thrinaxodon_, Early Triassic, South Africa, Antarctica

    Elaborate cheek teeth; large dentary, with coronoid process(for jaw joint), but still lower jaw of more than one bone; reduction to mammalian number of insisors; almost complete secondary palate – before anyone comes in here with the question "How could an almost complete secondary palate work?" - the palate can function quite adequetely by being covered with a fleshy membrane, which it is in reptiles. Thus the underlying bone can form gradually and support the palate more and more, without delateriously affecting the functioning of the palate, until the secondary palate if fully formed, it then becomes important, because it separates the nasal passages from the mouth - this means you can now eat and breath at the same time or more importantly you can breath whilst chomping something that is struggling to get away, or that something else is trying to steal from you); lumbar ribs reduced to small plates - the specialisation of the lumbar area is indicative of the presence of a diaphram, needed for higher O2 intake and homeothermy; the head of the femur is set at a considerable angle to the shaft - this indicates that the limbs were upright and closer to underneath the body that sprawling; adult/baby fossil assemblages have been found - possibly indicating parental care; fossils found curled up - curling usually indicates an attempt to keep body heat, possible homeothermy.

    C
    Cynognathus_, Early Triassic, South Africa

    Enlarged dentary, 90% of lower jaw, teeth differentiating, large canine, molars with cusps; secondary palate well developed; jaw joint quadrate-articular, but bones very small; scapular transverse and turned out - half way to mammal condition; limbs under body; possible evidence for fur in fossil footprints.

    D
    Diademodon_, Early Triassic, South Africa

    Cheek teeth more specialised, with more cusps, occlude together more efficiently; clavical ribs fused.

    E
    Probelesodon_, Mid Triassic, South America.

    Saggital crest for greater muscle attachment; nares separated; lumbar free.

    F
    Probainognathus_ Mid Triassic, South America.

    Additional cusps on cheek teeth; teeth double rooted; 'double' jaw joint, the quadrate-articular and the dentary-squamosal bones articulate, but the quadrate-articular bones are very much reduced and only loosely constrained in a groove in the dentary bone; cervical ribs very short; lumbar free; phalangeal arrangement mammalian - loss of some bones.

    G
    _Kayentatherium_, Early Jurassic, world wide.

    Double occipital condyle; secondary palate; separated nares; dentary bone covers almost all lower jaw; differentiated dentition; double rooted teeth; lumbar free; scapulare with spine; pelvic elements fused; fused clavical ribs; but quadrate-articular although very much reduced, still participate in the jaw joint. This feature classifies the organism as a reptile, even though it has far more mammal characters than reptile ones.

    Recap:

    A B C D E F G

    1 1 1 1 1 1 1 1

    2 * 1 1 1 1 1 1

    3 * * 1 1 1 1 1

    4 0 * 1 1 1 1 1

    5 0 0 * 1 1 1 1

    6 0 0 0 * 1 1 1

    7 0 0 0 0 0 * 1

    8 0 0 0 0 0 * *

    O = reptilian state
    * = intermediate
    1 = mammalian state

    This is by no means exhaustive and there have been some changes since I drew up this list. However, the basic principle still holds.


    There is a diagram showing the difference between mammals and reptiles here: http://www.mun.ca/biology/scarr/QA_vs_DS_jaw.htm

    A nice tree showing a few therapsid (later mammal-like reptiles) skulls can be found here http://www.kheper.auz.com/gaia/biosphere/vertebrates/therapsida/Therapsida.htm
    ...also, some detailed skull diagrams and more information on skeletal transformations can be found here http://phylogeny.arizona.edu/tree/eukaryotes/animals/chordata/synapsid_lichen/synapsida_synapomorphies.html

    After reviewing some of the websites mentioned in the previous post, a forum member named "backel" asked some questions:

    backel:
    There were afew other things about the teeth i.e. the canines etc that I noticed, but their focus seemed to be on the splitting of the jawbone and how that could have evolved into the formaiton of the ear, but I have a few questions for you.


    I don't think it's true that "their focus seemed to be on the splitting of the jawbone and how that could have evolved into the formaiton of the ear" since the jawbone transformation was just one of a large number of changes mentioned on the links I gave, and in the case of the jawbone the focus was on the changes in the jaw itself and not the inner ear...from John McLoughlin's Synapsida:

    Early tetrapods such as pelycosaurs possessed mandibles (lower jaws) composed of a dentary (tooth-bearing bone) associated with a number of thin plates of bone that originally served to strengthen the jaw as a whole. The hindmost of these bones, the articular, articulated (hence the name), or hinged, with the quadrate bone of the skull. In therapsids this arrangement persisted, but the new life-style of these progressive animals, with its growing emphasis on high consumption of energy for lots of activity, required precise manipulation of food in the mouth in order that it might be better broken down for efficient digestion. In these animals, the act of chewing was forcing changes in the structure of the lower jaws to strengthen them further and increase their biting leverage.

    In this process, the dentary bone was becoming longer and thicker in response to the increase in stress to which it was subjected. In addition, as the molar teeth came into being and were put to grinding up food, changes in jaw musculature forced changes in jaw conformation to permit good chewing. The most primitive therapsids had jaws whose muscles were mainly attached to the inner surfaces of both jaws and skull. In later models, however, the new masseter (chewing) muscles gradually appeared on the outside of the dentary bone, connecting this to the cheekbone. Other muscles arose from a new coronoid (crownlike) process that extended the rear of the dentary bone upward inside the arch of the cheekbone. These muscles inserted along the top and back of the skull, along the temporal bones, and hense are collectively called temporal muscles. Because of the increasing power of these muscles in higher therapsids, the dentary bone was becoming bigger and heavier at the expense of all the other little jawbones.



    You can see all of this in the sequence of skulls on the mammal-like reptile page at http://www.gcssepm.org/special/fr_cuffey_00.htm (this is an excellent page on the mammal-like reptiles, by the way, definitely worth looking at if you want more detailed info)

    Backel: Is there more than the jawbones and other dental fossils? I mean skeletally. It seemed that there seemed to be a little bit about ribs for a couple but it seemed mostly to revolve around the skulls.


    A lot of the most interesting skeletal differences between mammals and reptiles are in the skulls (not just the jawbones as you seem to be saying above) but there are some significant ones in the rest of the skeleton which are also seen transforming in parallel with the skull changes. The biggest one is the change in gait--reptiles walk in a sprawled-out posture, lifting one leg at a time and bending their spine in an s-shape as they move, while mammals carry their legs straight beneath them and flex their spine up and down rather than from side to side. In the mammal-like reptiles we see a series of intermediate gaits, finally leading to a basically modern mammal-like gait. Other differences between mammals and reptiles which can be observed transforming are fused vs. unfused pelvis, differences in the configuration of the phalanges (digits), fused vs. unfused clavical ribs, and the ribless lumbar (lower spine) vertebrae of modern mammals.

    From the page on "transitional forms" at http://members.aol.com/ps418/tran.htm

    Next, we'll consider phalanges. In most reptiles, the phalangeal formula is 2-3-4-5-4, whereas the mammaliam formula is 2-3-3-3-3. The early therapsids possessed the reptilian formula. In Thrinaxodon, the phalangeal formula is reduced to 2-3-4-4-3, close to the mammalian count, but still intermediate between the two conditions. The "extra" phalanges in digits 3 and 4 are very small, presaging their later absense. In later cynodonts, the count is reduced to the mammalian formula of 2-3-3-3-3.

    Whereas reptiles generally display ribs all the way back to the pelvis, mammals lack ribs in the pelvic region. The gradual loss of these pelvic ribs can be seen in the cynodonts or mammal-like reptiles.
    Probelesodon, for example, displays ribs all the way back to the pelvis, but the last several ribs are greatly attenuated. In other advanced cynodonts, such as Thrinaxodon or the tritylodonts, the pelvic ribs are absent altogether, as in the mammalian configuration.



    Backel: Do we know anything about their internal organs?

    I don't know anything about this either way; you'd have to ask a practicing paleontologist. It may be that certain aspects of the skeleton would allow scientists to infer things about their internal organs, but maybe not.


    Backel: There was something about there being some evidence of fur. What is that?

    I'm not sure if there's other evidence, but here's something mentioned in Synapsida:

    In addition to their secondary palates and shearing molar teeth, thrinaxodonts show further advances in food-processing suggested by the presence on the cheek area of their skull of foramina (little holes), through which nerves and blood vessels passed. Such equipment very likely supplied nourishment to active lip and cheek muscles, which in turn may have supported vibrissae (whiskers), sensory structures enabling them to feel their way about at night...the possible presence of vibrissea on these little cynodonts is highly significant, for the embryonic origins of whiskers are similar to those of hairs in general. In primitive ectothermic amniotes such the living reptiles, the skin conducts heat; these animals are dependent on outside temperatures in maintaining their internal temperatures, and must be able to soak up or dissipate heat as fast as possible. Thus their skin is dry and thin, conserving moisture in the body by means of waterproof scales while controlling heat transfer through blood vessels close to the scaly surface. We may justifiably assume (since no trace of skin covering remains in fossils) that the more primitive end of the therapsid line posessed a similar integument serving a similar purpose.

    No one knows exactly how hair was derived from such skin surfaces. Some students have suggested that it evolved directly from the keratinous (horn) scales of primitive therapsids, much as did the feathers of birds from the scales of primitive archosaurs. However, unlike either scales or feathers, which develop from the epidermis, hair arises from a deeper layer of the skin. The presence of those little holes on the cheek areas of some cynodonts suggests that thick nasal skin may have supported projections similar to those on some living snakes, projections that were perhaps antecedent to the honest-to-goodness whiskers of the sort we find on cats and mice. The gradual spread of such whiskerlike appendages across the cynodont integument not only augmented their efficiency at detecting insect prey in the dark but also served to trap air near the body surface and thus insulate the little animals against the nighttime cold.



    Backel: Is there any hypothetical situation, or progression which shows these "freed up" bones "becoming" the bones which are the basis of the mamallian ear, or is it scientific conjecture of what could have happened with those bones.

    We have a progression in which the articular and quadrate become smaller and smaller and more "freed up" from their previous role in hinging the jaw, but the actual transformation into middle ear bones is not seen—probably past a certain point these bones would become too small to have much chance of being fossilized. The strongest line of evidence for the transformation is embryological--in mammal embryos the malleus and incus start out at a position just behind the dentary as in reptiles, and then migrate to the adult position in the middle ear as the embryo develops. And again from the transitional forms page http://members.aol.com/ps418/tran.htm :

    There are several lines of evidence which converge in support this conclusion. First, the progressive reduction in size and increase of mobility of the postdentary bones is clearly seen in the cynodont fossil record. For instance, Dimetredon, the therocephalians, Thrinaxodon, Probainognathus and Morganucodont show the postdentary bones in progressively more reduced form, and illustrate the step-wise transformation from the reptilian to the mammalian configuration. Second, "the malleus articulates with the incus in exactly the same way as the articular articulates with the quadrate in advanced therapsids and the quadrate (incus) articulates with the stapes" (Carroll, 1988, p 395).
    Third, the ontogeny of the incus and the malleus reflects or recapitulates their reptilian derivation. When marsupials are still in the pouch, for instance, "the malleus and the incus maintain the reptilian role of the articular and quadrate. Only when the young leave the pouch do these bones seperate from the lower jaw and enter the middle ear" (Carroll, p. 395; see also Crompton and Jenkins, 1979; McGowan, 1984). Yet again, the evidence from the fossil record, comparative anatomy and developmental biology converge in support of the same evolutionary sequence.



    In Synapsida, McLoughlin explains how the transformation is believed to have occurred:

    Now, we recall that in the long-lost days of the Pennsylvanian and early Permian, our ancestral line was represented by the pelycosaurs, a low-slung crew indeed. Because of their posture, these animals spent a lot of time with their heads, and thus their lower jaws, resting on the ground. Which had its advantages. The ears of these early tetrapods appear to have been as yet ineffecient at picking up airborne vibrations such as those we call sound. For these early landlubbers, fresh from the water, the only necessity for hearing was related to detection of the footfalls of potential predators, "sounds" that are transmitted well enough by the bones of the lower jaw from the ground to the balance organs of what we now call the inner ear.

    These balance organse were (and still are) fluid-filled structures equipped with nerve ends highly sensitive to movement of the fluid. In early tetrapods, extensions of these balance organs came to be associated, in the form of the hyomandibular bone, with part of old tongue-support mechanism in fishes. Originally supporting part of the upper-jaw rims with the tongue, this little bone aided the transmission of vibration to the balance organs. As land vertebrates got better at detecting airborne vibration through the jawbones, the hyomandibular was reduced in size to become the stapes (stirrup), connecting the typanum (eardrum) to the cochlea (snail-shell-shaped inner ear). Air vibrations moving in the tympanum thus moved the stapes, which wiggled the fluid in the cochlea, which alerted the brain.

    This is the way the ancestors of reptiles, archosaurs, and birds took to hearing, and it served them very well. The therapsids, however, were forced along a different route as their hearing improved. As the subtlety of land-lubbing increased, synapsids continued for a time to keep their jaws to the ground in hopes of picking up noise; in them the tympanum stretched alongthe rear of the jaw in such a way as to be intimately associated with the articular bone. As the dentary bone increased in size, however, a conflict arose: increase in chewing efficiency forced an increase in dentary size at the expense of the little articular bone, which was still necessary for hearing. Increased chewing efficiency threatened hearing acuity: how would it work out?

    Ultimately, the little jaw-joint bones, the articular and quadrate, receded into the head as cynodont evolution progressed. With the inception of the mammalian jaw joint--that is, one between the dentary mandible and the squamosal cheekbone--these tiny bones were entirely freed from their function with relation to the jaw. They continued to be joined together, however, and their ancient articulation with one another persists as they transmit sound from the eardrum to the cochlea. Here they remain, and here we hear, still listening with parts of our mouths in the manner of our ancestors 300 million years ago.
     
  2. Administrator2

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    JOHN PAUL
    Looks like we have some better hearing reptiles.

    First how do we know that one specimen 'evolved' into the other?
    Second would be where were each of the fossils found? Why is that important? Well if one fossil is found in South America and its next alleged kin is found in Asia, how is that evidence one evolved into the other? So without the location of the fossil finds any connection between the apparent sequence can be very misleading.

    The reasoning of putting together fossil 'lineages' is circular because it assumes the ToE to be indicative of reality.

    Also is there any biological or genetic evidence that such a transformation (reptile to mammal) is possible?



    LIVEFREEORDIE
    The whole point here, JP, is that the existence of these transitional forms in an undisputable FACT. The theory of evolution predicts that we should find exactly this sort of thing. Do you know of an alternative theory that explains these facts equally well?


    The reasoning of putting together fossil 'lineages' is circular because it assumes the ToE to be indicative of reality.

    The "lineages" are hypotheses developed to explain the facts at hand: the transitional fossils and their temporal and spatial distribution. If you don't believe evolution best explains these facts, then what theory do you think explains them better?


    Also is there any biological or genetic evidence that such a transformation (reptile to mammal) is possible?

    For all we currently know about genetics and microbiology, there is nothing to remotely suggest that such a transformation is impossible. No one has found any evidence of a mechanism that would limit the amount of change an organism is subject to.


    JOHN PAUL
    The whole point here, JP, is that the existence of these transitional forms in an undisputable FACT.

    But transitional from what to what is the question.


    The theory of evolution predicts that we should find exactly this sort of thing.

    Really? I have heard that there is NO way to predict what would be selected for at any point in time. That was from the PBS series on 'evolution'.


    After all, if a "primitive" form were found in a later strata than an "advanced" form, that would be pretty compelling evidence against evolutionary theory.

    Not really. It may put a damper on that particular alleged lineage, but that is about it.


    For all we currently know about genetics and microbiology, there is nothing to remotely suggest that such a transformation is impossible.

    That is not so. Please any evidence to back up your assertion would be appreciated.


    No one has found any evidence of a mechanism that would limit the amount of change an organism is subject to.

    David Plaisted thinks protein structure argues against the ToE. That would be one. However it is uop to evolutionists to provide biological or genetic evidence to support their theory. As yet they have failed to do so.


    EDGE
    The reasoning of putting together fossil 'lineages' is circular because it assumes the ToE to be indicative of reality.

    Interesting assertion. Tell us then why the fossil record was recognized at the end of the 18th century, but evolution didn't come along till later.


    Also is there any biological or genetic evidence that such a transformation (reptile to mammal) is possible?

    Well, for one the fossil record is biological, and there are plenty of other forms of evidence to support the transformation. I know that you don't accept it, but most scientists do. Now, then, what is your evidence?


    JOHN PAUL
    What was the fossil record recognized for at the end of the 18th century? What lineages were made at that time?
    That IS what I was talking about...


    Well, for one the fossil record is biological,

    The fossil record is biological? That is your answer? Sorry edge, biology deals with living organisms and vital processes. Paleontology deals with fossils.


    and there are plenty of other forms of evidence to support the transformation.

    Like what?


    I know that you don't accept it, but most scientists do.

    Accepting it is not scientific. Let's see some of this other form of evidence. You talk about, now present it.


    Now, then, what is your evidence?

    My evidence for Creation is DNA, the cell and life itself. Along with the fact there is no existing empirical evidences that show such transformations are possible.


    EDGE
    What was the fossil record recognized for at the end of the 18th century? What lineages were made at that time? That IS what I was talking about....

    Hey, I was just asking a question. If you can't answer it, that's fine.

    So, paleontology has nothing to do with biology? Paleontologists don't use biological principles and biologists have not examined the fossil record. I stand corrected.

    Edge: and there are plenty of other forms of evidence to support the transformation.

    John Paul: Like what?


    Like the fossil record.


    Let's see some of this other form of evidence. You talk about, now present it.

    Kind of a knee-jerk assertion, is that not JP? Do you accept anything? Accepting evidence is not scientific? And accepting supernatural events IS scientific? Accepting mechanisms and designers for which there is no evidence IS scientific? No, let's just ignore the fossil record, since there is no mechanism that JP will accept.


    My evidence for Creation is DNA, the cell and life itself.

    Ah, but your interpretations DNA, the cell and "life itself" are unwarrented and ignore other evidence. Besides, we use the same evidence so you must be wrong.


    Along with the fact there is no existing empirical evidences that show such transformations are possible.

    There is only empirical evidence that it has happened. Now, you tell us how, in your own words.


    HELEN
    You might be interested in "Reappraising the 'Crown Jewel'" which deals with this 'evolution' from reptile to mammal: http://www.trueorigin.org/therapsd.asp


    QXR37
    John Paul:
    Looks like we have some better hearing reptiles.


    If you look at the skull diagrams, you'll see it's a lot more than that. There are a whole lot of different features that clearly distinguish mammal skulls from reptile skulls, and all of these can be seen transforming in parallel from the typically reptilian configuration to a typically mammalian one. There's not even a clear dividing line where "mammal-like reptile" leaves off and "mammal" begins--one of the first specimens classified as a "mammal," Morganucodon (second from the top in the skull diagram), still retained features of mammal-like reptiles, like the remnants of a reptilian jaw joint which had not yet transformed into the bones of the inner ear.


    First how do we know that one specimen 'evolved' into the other?

    Of course there's no way to be sure just by looking at fossils, which don't come with birth certificates. However, degree of "mammal-likeness" very closely conforms with their order in time--if you look at the page I got the skull diagrams from, you'll see that these examples are actually shown in their correct chronological order: http://www.gcssepm.org/special/fr_cuffey_00.htm

    And of course, there's also the fact that no mammals can be found before the permian when mammal-like reptiles begin to appear; in fact, the first "mammals" appear a little after the most mammal-like mammal-like reptiles, and as I mentioned the line between mammal-like reptile and mammal is drawn somewhat arbitrarily.


    Second would be where were each of the fossils found? Why is that important?

    A great many--perhaps the majority--of mammal-like reptiles do in fact come from a single location, the Karroo fossil beds in South Africa, home to hundreds of these fossils. Robert Broom, the discoverer of many of them, said in 1932:

    If we except the Pliocene age, ... there is no period in the world's history so important as that from the Middle Permian to the Upper Trias, as it was during this time that a group of reptiles slowly evolved into more and more mammal-like forms, and ultimately gave rise to primitive but true mammals.

    And in the South African Karroo shales we have a nearly continuous history of the land animals of this important period, and the study of various beds is like examining the pages of a book of history.



    This is from "The Ecology and Biology of Mammal-like Reptiles" (edited by Hotton, MacLean, Roth, and Roth), p.1...after the quotation by Broom, the author of the article also mentions this:

    In Permian times, long before the dinosaurs, the mammal-like reptiles populated the world in great numbers. Their remains have turned up on every continent, recalling Alfred Wegener's (1915) original contention that 250 million years ago the earth formed a single land mass, which he called Pangaea. Between 1969 and 1971, fossils of mammal-like reptiles found in Antarctica were the same kind as those in the Karroo beds of South Africa. Antarctica had been connected to South Africa, forming part of the great southern continent, which Edward Suess (1904) called Gondwanaland because the strata of the untilted table mountains of Africa and South America resmebled those of the Gondwana region of India.


    Here are some sites on the Karroo fossil beds (also often spelled 'Karoo,' I gather):

    fossil reptiles of the south african karoo http://www.museums.org.za/sam/resource/palaeo/cluver/index.html

    Barren Karoo's fossil treasure house http://www.mg.co.za/mg/news/98june2/30june-karoo.html

    Robert Broom http://sasap.freeservers.com/australopethicus/mother_of_the_nation.html


    The reasoning of putting together fossil 'lineages' is circular because it assumes the ToE to be indicative of reality.

    It's also based on location and order in the stratigraphic record.


    Also is there any biological or genetic evidence that such a transformation (reptlile to mammal) is possible?

    What kind of evidence are you looking for? How about the embryological evidence showing that the middle ear bones start out in the position of the reptilian jaw joint? Or how about circumstantial evidence from monotremes (the platypus and echidna) which display a large number or reptile-like features, such as:

    --egg-laying

    --poor temperature regulation (i.e., closer to "cold-bloodedness" than any other mammals):

    (from this page) http://rainbow.ldeo.columbia.edu/courses/v1001/21.html

    --only a single body opening for both waste and reproduction, similar to reptiles and birds but unlike other mammals (this is where the name 'monotreme' comes from):

    --According to this page, "Once hatched in early November, the young is suckled by the female which has no teats. Milk is produced in large glands under her skin which can be up to one-third of her body's length. The milk oozes out onto a patch of fur and the young Platypus sucks it up." http://www.healthsci.utas.edu.au/physiol/mono/Platpage.html

    --this page also mentions some other reptilian characteristics, namely cervical ribs and "local ascorbic acid synthesis in the kidney." And talkorigins also mentions that "there are a number of skeletal features of the pectoral girdle that are found only in therapsids, extinct mammal-like reptiles thought to be ancestral to mammals. This mixture is even found at the cellular level; the chromosomes and sperm of platypuses display both reptilian and mammalian traits." http://www.fortunecity.com/meltingpot/albania/323/ http://www.talkorigins.org/faqs/platypus.html -- talkorigins

    I doubt you'll find any of this very convincing though. Other than actually turning a reptile into a mammal via genetic modification, can you think of any "biological or genetic evidence" that you would actually accept?


    JHAPPEL
    Just curious. Where are the transitionals that would be easy to see that would make irrefutable proof of evolution? For example turtles. Turtles fossilize better than any other animal. Yet not a single transistional has ever been found. Or how about bats. It must have taken countless generations to evolve a mammal that crawled to a flying mammal with sonar and yet not a single transistional has ever been found. Or how about pterodactyls. Again there should be abundance of transistional evidence for these specimens yet nothing has ever been found.
    How about birds? Archeopraptx had fully evolved feathers and could probably fly. Where are the feather transistions showing how this evolution took place and how the body had to evolve its shape to allow flight?
    Nothing has been found. Or how about the evolution of dinosaurs? These speciman should be clear and evolution of these should be obvious since they supposedly existed for 165 million years and would be preserved easily.
    Where is the origin of horns, duck-bills, spikes, plates, crests, bony domes, etc. Not a single transistional has been found. No more exuses. The fossil record is very much complete and the transistionals are not there. If evolution is true these are the transistionals that we should find that would make evolution a open and shut case yet they are criminally absent.


    LATE CRETACEOUS
    As a matter of fact, there are some excellent examples of the dinosaur-bird evolution, including the evolution of feathers (they started out similar to Emu feathers on small theropod dinosaurs).

    sinosauropteryx was had the skeleton of a dinosaur, but with an integumen of downy feathers

    Sinornis, Confuciusornis, Protarchaeopteryx and Caudipteryx are good examples of transitionals. http://www.peabody.yale.edu/exhibits/cfd/CFDintro.html

    X-ray analysis of birds in flight show that their wing-flapping motion is identical to the theoretical attack motions of dinosaurs like velociraptor and other dromeasaurids.

    I know you are likely to bring up the archeoraptor fiasco, but what does it proove? If a fake van-gough were discovered in a museum, would that mean all van-goughs in museums are fakes (something like that happened not to long ago)? Does the Bre-X fraud mean that all new gold discoveries are fake? Of course not, but they do cause greater vigilence.


    QXR37
    You might be interested in "Reappraising the 'Crown Jewel'" which deals with this 'evolution' from reptile to mammal: http://www.trueorigin.org/therapsd.asp

    I've read it, but I don't find it very illuminating. It basically ignores the clear overall pattern and tries to create "reasonable doubt" by showing that there's controversy over the specific interrelationships between individual branches of the mammal-like reptile family tree. On this arn.org thread a forum member criticized the article in a little more detail, http://www.arn.org/ubb/Forum1/HTML/000443.html:
     

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