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RE: birds/dino-birds with teeth



Larry Febo wrote:

> I`m sure this has been argued before (check the archives), but the
> "standard" answer to this question, back in my undergrad days (way
> back), was that it was part of the evolving avian form in an attempt to
lose
> weight and be therefor better adapted for flight. 

Makes perfect sense.  Except for one thing: most Mesozoic birds had teeth.

Loss of teeth appears to have occurred several times in avialan evolution
(confuciusornithids, gobipterygids, neornithines); but most volant
non-neornithine birds had teeth (e.g. _Liaoxiornis_, _Jibeinia_, _Yanornis_,
chaoyangiforms, ichthyornithiforms, the majority of enantiornithines).  In
the majority of avialan lineages, the postcranium was drastically
re-organized toward a more powerful and efficient flight apparatus.  For
most groups of avialan taxa, the teeth stayed resolutely in the jaws.
Neornithines (which appear not to have been so common in the Cretaceous -
though this may be a preservational artifact) were unusual in being
completely toothless.

Also, many primitively flightless theropods were toothless
(ornithomimosaurs, oviraptorosaurs, ?avimimids, _Yandangornis_ - if it's
loss of flight ability isn't secondary).



Tim

------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163