Re: quick ?: dinos and birds

[RaptorRKC@aol.com]

Landry:

Birds are not the closest extant relatives to dinosaurs; they -are- dinosaurs,
in fact, they are advanced maniraptoran theropods and probably the sister
group to dromaeosaurids.  

Dinosaurs were at one time suspected to be diphyletic (that is, having evolved
from two separate ancestors and grouped together without including the groups'
common ancestors), but recent research has proven that dinosaurs really are
monophyletic after all.  Dinosaurs are united by a suite of characters, which
includes specializations in the limbs, three or more sacral vertebrae, and a
perforate acetabulum (the lattermost feature having been subsequently lost in
advanced avians).  

Since birds are dinosaurs, the closest extant relatives must therefore be
crocodylians, the only living archosaurs aside from birds.  As both dinosaurs
and lepidosaurs (lizards and the like) are reptiles (in the modern sense),
they are related to some extent, but not closely.  Crocodylians are more
closely related to birds than they are to lepidosaurs! 

Well, I hope that helps clear things up.

Rachel Clark

"You will respect my authori-TAY!"