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RE: The birds vs. the pterosaurs



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Steve Doolittle
>
>  It
> seems to me
> that whatever element killed off the larger dinosaurs at the end of the
> cretaceous wouldn't have killed off some of the smaller pterosaurs that
> survived right to the end of the cretaceous.

Two things here:
Minor point A) We have, at present, no fossils of smaller pterosaurs at the
end of the K.  This is not to unequivocally say that they were gone (their
fossil record is spotty), but there is no poisitive evidence of their
presence at that time.
MAJOR HONKING POINT B) The K/T boundary is not merely the end of the
dinosaurs (exclusive of neornithines); it is a HUGE extinction affecting
many lineages of organisms, both terrestrial and marine.

> It's like Bob
> Bakker says about
> mass extinctions:  It's always the larger animals that get hit.

Sorry, but this is just plain wrong.  This pattern does not hold for most
extinctions, and it certainly isn't true of the marine realm at the K/T.
While it is true that in the K/T *terrestrial* extinctions that large-bodied
vertebrates suffered far greater extinctions than small guys, this isn't
absolute.  There are other factors in effect: for example, the death of the
enantiornithes vs. the survival of the similarly sized neornithines.

> When the mass
> extinction occurred in the late cretaceous, who died?  Certainly not the
> smaller dinousaurs.  Not the turtles or the little mammals or the little
> birds.

EXCEPT: some groups of mammals suffered greatly (for example, there were
extinctions among many of the groups of North American metatheres (marsupial
relatives)), and all lineages of birds except for neornithines died out.

Also something to keep in mind: there is not a single fossil of a pterosaur
from above the K/T boundary.  The evidence for their survival into the
Tertiary is precisely as good as the evidence for ceratopsid or
tyrannosaurid or titanosaurian or mosasaurid or ammonoid survival into the
Tertiary.

Hope this helps.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796