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Re: Drinker and Oryctodromeus (was Re: Dinosaurs burrowed to keep warm)

Dann Pigdon wrote:

Perhaps burrow-dwelling is primitive for hypsies, or even basal ornithopods? I've read that Heterodontosaurids lacked stiffening tendons in their tails.

Also, back in the 1970's, Thulborn proposed that heterodontosaurids hibernated (or aestivated) during the dry season. But this was based on tooth wear patterns (ihe thought that heterodontosaurids replaced their teeth wholesale only once a year, and had to avoid feeding during this period). AFAIK there was no taphonomic evidence to support this hibernating behavior. The idea went over like a lead balloon (heterodontosaurids could in fact replace their teeth continuously). Hopson even named a heterodontosaurid _Abrictosaurus_ ("awake lizard") to express his skepticism.

_Heterodontosaurus_ itself had powerful forelimbs, based on the prominent deltopectoral crest and olecranon process. Weishampel and Witmer (1990) suggested that heterodontosaurids dug up tubers and roots with their forelimbs.

If burrowing is primitive for ornithopods, then it would make sense for this behavior to be retained in critters like _Atlascopcosaurus_ and _Leallynasaura_, which had to endure those long polar winters in SE Australia.

Those 'eyelid bones' above the eyes would also have provided good protection from collapsing burrow material (or just plain bumping their head on the ceiling).

Hey maybe that's why the pachycephalosaurs evolved really thick skulls! After all, there is evidence that heterodontosaurids are closely related to pachycephalosaurs. Those thick skull roofs served as 'hard hats'! ;-)



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