Re: Re: Mesozoic-ware

[Thomas_R_HOLTZ@umail.umd.edu (th81)]

>>
>>    Dinosaurs certainly are reptiles.
>
>       That depends on what one defines to be a reptile. Under certain 
>definitions of reptile (cold blooded, sprawling legs) dinosaurs don't 
>fit.

Of course, that definition also included amphibians, so it's not very useful.

> Under others, they do. But then, if dinosaurs are reptiles, what are
>birds? Birds are dinosaurs, so does the commutative property (A=B, B=C, so
>A=C) apply here and make them reptiles?

Yep.  As Gauthier and others have shown, birds share MANY derived soft- and
hard-tissue features uniquely with turtles, lepidosaurs, and crocs among
living animals.

> I suppose we could argue they're
>sufficiently different from dinosaurs to qualify for their own class, but 
>we still consider bats mammals, too, and dinosaurs have some significant 
>differences of their own.  



Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD  20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084