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Re: New ankylosaur from Liaoning

Ken Kinman (kinman@hotmail.com) wrote:

<This is probably a really dumb question, but what would be the 
difference between the transverse ossified belly "planks" of
aetosaurs and belly ribs (gastralia)?>

  It's a sane question, Ken.

  Gastralia are dermal bones, as are portions of the skull, the
pelvis, and the shoulder girdle and ribs. These form from
non-endochondral bone, unlike the limb bones, vertebrae, braincase,
and palate. Dermal ossicles form within the skin as a concretion,
somewhat similar to dermal bone, but they also form with follicles
producing keratin, as in crocodile scutes, and are intrinsically
involved in the external structure thus far, rather than becoming
subdermal. Aetosaurs have both, for one thing; gastralia and ventral
plates; the nodular dermal ossicles in ankylosaurs are of similar
apparent origin, but form as nodes rather than plates, and no known
ankylosaur has developed "truly" plate-like elements. This also in
the light of no gastralia in ankylosaurs, the elements are not
congruous to the form of modified gastrale elements, being nodular
and supernumerary, as well as irregularly arranged in the most basal
ankylosaurs (*Liaoningosaurus* and *Minmi*).

Jaime A. Headden

  Where the Wind Comes Sweeping Down the Pampas!!!!

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