The Mammal-like Reptiles, Dr Duane T Gish; Some Observations

http://www.icr.org/pubs/imp/imp-102.htm A literal creationist perspective, including Kuehneotherium. Before reading the above essay I wrote, "Unlike myself, Dr Gish is a trained and experienced scientist, who is entitled to be respected as such." However, I have now read it and offer a couple of observations, which you’re free to ignore. a. Both the reptilian and mammalian jaw joints are present in Pachygenelus and nobody calls it a mammal. b. The views of Gould and Eldredge on Archaeopteryx are crassly misrepresented. They saw it not as a smooth, but certainly as a clear transitional form. What is Archaeopteryx doing in this essay anyway? c. Dr Gish argues convincingly that the duck-billed platypus cannot be the ancestor of modern mammals!, and uses an exclamation mark for emphasis. As this is blindingly obvious, this conclusion is utterly pointless. Need I add that I did not father my great-great-etc grandparents, or indeed distant cousin? (Thanks for the suggestion, Truman). d. His 'essential extinction' of the mammal-like reptiles occuring simultaneously with the emergence of the mammals, is simplistic rot. The larger carnivores and herbivores are unknown beyond the Carnian, (early Upper Triassic), and were in no way replaced by the mammals. Smaller representatives persisted until at least the Upper Jurassic, and possibly into the Lower Cretaceous, (see Jurassic Cynodonts). e. Because mammals were able to diversify dramatically during the Tertiary and beyond, it does not reasonably follow that the same would have been inevitable during the Jurassic or Cretaceous. The world is a complex place and conditions, (and the competiton), were very different. There are factors known as change, opportunity and luck. f. With some reptiles, the jaw bones actually work in concert with the ear to enhance the sense of hearing. They also manage to eat. g. "Whether the dentary bone of these creatures actually made contact with the squamosal can only be inferred. But if there had been a real contact between the dentary and squamosal, could it be said that this constituted a mammalian jaw-joint which existed alongside the reptilian jaw-joint?" If a reptilian jaw-joint exists alongside a mammalian one, than of course it could also be said that the mammalian joint co-exists with the reptilian one. This has something to do with the meaning of the word 'alongside'. h. As regards Kuehneotherium, Dr Gish informs us that the ear of this creature was that of a standard reptile. It's ear isn't actually known for sure, but one site where it occurs in Wales did provide some not terribly well-preserved petrosals. These are the bony casing around the ear and, as this bone happens to be hard, prospects for fossilisation are relavtively high. With existing animals, petrosals are only found with mammals. The casing of the ears of other animals is built by several bones, not a singleton. They're of the right sort of size for Kuehneotherium. The again, as they were only found in association with Kuehneotherium fossils, rather than in articulation, perhaps they might belong to something else not yet identified. If so, then the fossil record of kuehneo ears is zilch. That would mean Gish's assertion is based on non-existent evidence in this case. The most common kuehneo fossils are the teeth, some of which are well preserved. I’ve just read about one from Syren, Luxembourg. It has traces of the roots (plural). These are mammal-style teeth. Comparative studies show them to be broadly similar to symmetrodont teeth, as in Mammalia:Symmetrodonta. In the case of Morganucodon, reasonably well preserved skulls are known from China. The ear did indeed have only one bone; the stapes. So did the casing of the ear. This is contributed by a bone called the petrosal. And, as said above, that's a characteristic only found now in mammals. And what about the teeth? These are also mammalian. They most closely resemble those of the triconodonts, as in Mammalia: Triconodonta That is why Morganucodontidae was often placed within this order. Owen diagnosed Triconodon ferox as a mammal about 140 years ago, albeit erroneously as a marsupial. Lots of bits of morgauncodontid jaws are available for study, and not one of them shows evidence of any more than a single episode of tooth replacement. Of animals with teeth, only one group experience a single episode of dental replacement, and they're known as mammals. (For an abstract on basal mammal ears see, Luo, Crompton & Lucas, JVP, 1995 ). i. "All mammals, living or fossil, have a single jawbone, a fully developed mammalian jaw-joint, and a vastly different auditory apparatus involving three bones in the middle ear and a totally unique and extremely complex structure, the organ of Corti." All mammals do share these characteristics, if that's how you choose to define Mammalia. As well as employing this highly unusual diagnosis, Dr Gish also presents assumptions as fact. I know little of the organ of Corti, other than it's clearly microscopic and composed of soft tissue. It's just the sort of thing which is highly unlikely to fossilize. I've no idea how it might have evolved, because there is no fossil record to go by. Consequently, how does he know that all mammals had this organ, in its fully developed form? Also worth knowing is that both Morganucodon and Kuehneotherium had "a fully developed mammalian jaw-joint". (With thanks to Wesley R. Elsberry for some good advice.) If, purely out of the spirit of friendship, I were to accept Dr Gish’s assertions as to the standard reptilian nature of the jaws and the ears of Kuehneotherium and Morganucodon, then we end up with reptiles with mammalian teeth. Might I suggest that it’s not unreasonable to mention the term, transitional? These, and other points, have prompted a revision: Unlike myself, Dr Gish is a qualified scientist. "That article was interesting. Are there any more on-line?" I'm pleased you asked. Have a look here. Trevor Dykes (not a paleontologist), April 2001 (some additions and amendments, 4.7.2007) ktdykes@arcor.de Back to top