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Re: erect crocodile problems

In a message dated 98-06-09 10:31:47 EDT, tonyc@foe.co.uk writes:

<< Are not crocodiles descended from bipedal ancestors? If so, they were
 either ectothermic bipeds or endotherms with ectotherm descendents? >>

Alas, no. But modern crocs are quite likely descended from small, erect-
limbed, cursorial quadrupedal forms. The most interesting evidence for this
lies in the elongated carpal bones of crocs, which apparently appeared in the
Triassic as a running adaptation (to elongate the forelimb) and which are
retained--uniquely among tetrapods, as far as I know--in extant forms. This
could imply that endothermy is not necessary for the development of an erect
posture or cursoriality, since extant crocs aren't endothermic--except that it
remains possible that extant crocs are secondarily ectothermic (that is, their
cursorial ancestors became endotherms but lost this adaptation along with
their cursoriality).