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Re: crocodylomorphs?/ birds



>1) what is a crocodylomorph?

Crocodylomorphs are crocodilians (crocs, alligators, gavials, etc.) and
some of their extinct relatives.

>2) so the current theories re birds are 1) they and the dromaeosaurs came
>from the same stock, and branched apart during the early jurassic

Yes.

>
> 2) dinosaurs are an offshoot from reptiles to birds

Not exactly.  Depending how you define the term reptiles (now generally
considered the common ancestor of turtles, lizards (including snakes),
tuataras, and crocodilians and all descendants of that common ancestor),
dinosaurs are a subgroup of reptiles, and birds a subgroup of dinosaurs.

>4) are archaeopteryx and protoavis properly considered birds (if only
>barely), or are they their own group?

In most taxonomies, "barley" is enough.  Depending on the scientists,
Archaeopteryx is in Aves (i.e., birds) or the larger group Avialae ("Bird
Wings").

The material called Protoavis is not very convincing, and has not been
shown to be either a) a bird or even b) a single species.

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.