Pneumaticity in basal Archosauria -- _Naturwissenschaften_

["Jaime A. Headden" <qilongia@yahoo.com>]

Gower, D.J. 2001. Possible postcranial pneumaticity in the last
common ancestor of birds and crocodilians: evidence from
*Erythrosuchus* and other Mesozoic archosaurs.
_Naturwissenschaften_ 88(3): 119-122.

  [suggests that *Erythrosuchus* bore postcranial pneumaticity
of a like with birds, that therefore, crocs are secondarily
un-pneumatized in the manner of birds themselves. Not
specifically about dinosaurs, but suggests that they are
plesiomorphically pneumatic, and that birds are expansionist on
this degree, not innovators....]

The abstract reads:

  "Birds and crocodilians (extant archosaurs) have differing,
distinctive morphologies. Birds have respiratory airsacs with
diverticula that pneumatize the postcranial skeleton, a feature
absent in crocodilians. Bony correlates of pneumatic sinuses are
known in the vertebrae of some non-avian dinosaurs and in
pterosaurs - taxa more closely related to birds than
crocodilians. This and the apparent absence of pneumatic
postcranial bones in fossil archosaurs more closely related to
crocodilians than to birds, has been interpreted as evidence
that postcranial pneumaticity is a derived character of birds
and their nearest fossil relatives. The presence of apparent
osteological correlates of postcranial pneumaticity is here
reported in some non-crown-group archosaurs, and some of the
fossil taxa more closely related to crocodilians than to birds.
This suggests that the last common ancestor of birds and
crocodilians might have had a pneumatized postcranium, and that
the absence of this feature in crocodilians might be derived."

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