There are no transitional forms between reptiles and mammals.
Two genera (Probelesodon and Massetognathus) of the cynodonts, a small subdivision of the synapsids, display characteristics of both reptiles and mammals, as well as qualities that are ambiguous between reptiles and mammals. The reptilian features are:
The mammalian features are:
The ambiguous characteristics are:
Probainognathus, another genus of the cynodonts, has both reptilian and mammalian jaw joints, and shows the first step in the change of the reptilian jaw joints into the mammalian ear ossicles. This does away with the creationist charge that a reptile-mammal transitional form could not have chewed its food while its jaw was being unhinged and repositioned for hearing (McGowan 1984:139). Also, Probainognatus would have had no trouble hearing during rearticulation, as reptiles exploit the transmission of sound from the ground through their jawbones (Kitcher 1982:111).
Kitcher P. 1982. Abusing Science: The Case Against Creationism. Cambridge, Mass: MIT Press.
McGowan C. 1984. In the Beginning...: A Scientist Shows Why the Creationists Are Wrong. Buffalo: Prometheus.
Last updated: 21 Mar 2008
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