Re: "Dinosaurs Died Within Hours After Asteroid Hit Earth..."

[Dora Smith <villandra@austin.rr.com>]

What about them cow-sized herbivorous mammals?

Yours,
Dora Smith
Austin, Texas
villandra@austin.rr.com
----- Original Message -----
From: "David Marjanovic" <david.marjanovic@gmx.at>
To: "DML" <dinosaur@usc.edu>
Sent: Saturday, May 29, 2004 12:27 PM
Subject: Re: "Dinosaurs Died Within Hours After Asteroid Hit Earth..."


> > > *cough* deinonychosaurs *cough* oviraptorosaurs
> > > *cough* segnosaurs ...
> > >
> > > Mickey Mortimer
> >
> > *Cough* Land-dwelling critters much LARGER than most
> > birds.  VERY UNLIKELY to have been living in burrows.
> > And, given the birds super-light construction, much
> > heavier (thus requiring much more food by an even
> > larger factor than did birds.)  Ever heard of "Occam's
> > Razor"? *Cough*
>
> So you agree that the feathers alone can't have been a reason? :-)
>
> I think you overestimate the "super-light construction" of birds. They
> aren't so much more pneumatic than an oviraptorosaur or dromaeosaur, and
> have the added weight of flight muscles. *Bambiraptor* was quite small,
> easily comparable to Presbyornithidae -- an anseriform group that
survived.
>
> I do think you're right that food has to do with the question. Segnosaurs
> (as herbivores) and dromaeosaurs (as rather ordinary carnivores), at
least,
> were pretty directly dependent on green plant parts; the surviving bird
> groups, as far as known, were not (galliforms can eat seeds, earthworms
and
> burrowing insects, anseriforms eat aquatic debris, the others I mentioned
> eat fish which in turn eat aquatic debris...).
>
> I recommend
>
> Gregory J. Retallack: End-Cretaceous Acid Rain as a Selective Extinction
> Mechanism between Birds and Dinosaurs, 35 -- 64 in Philip J. Currie, Eva
B.
> Koppelhus, Martin A. Shugar & Joanna L. Wright (eds): Feathered Dragons.
> Studies on the Transition from Dinosaurs to Birds, Indiana University 2004
>
> Abstract:
>
> "Acid would have been a consequence of catastrophic events postulated for
> the Cretaceous-Tertiary boundary: nitric acid from atmospheric shock by
> bolides and from burning of trees; sulfuric acid from volcanic aerosols
> [boo!] and from impact vaporization of evaporites; hydrochloric acid from
> volcanic aerosols [boo!]; and carbonic acid from carbon dioxide of
> volcanoes, fires, and methane-hydrate release. Pedoassays [erm... Greek:
> pedon = soil] for buffering of soil acid above pH 4 are indicated by the
> clayey, little-leached nature of latest Cretaceous and earliest Tertiary
> paleosols in Montana. Chemoassay of 2.7 x 10^11 to 4.6 x 10^17 moles of
acid
> has been estimated from base-cation leaching of Cretaceous-Tertiary
boundary
> beds and paleosols in eastern Montana, and these estimates are compatible
> with other independent chemoassays. Marine bioassay of pH suppression to
no
> less than 7.6, allowing survival of coccolithophores, foraminifera, and
> dinoflagellates, requires a total acid load of less than 5 x 10^16 moles.
> Similar limits come from a non-marine bioassay of pH suppression to less
> than 5.5 but no less than pH 4, allowing survival of amphibians and fish,
> but strong extinctions of non-marine mollusks in Montana. Acidification
also
> may have been responsible for heavy extinctions among evergreen
angiosperms.
> Vegetation browning would have been difficult for herbivorous dinosaurs
and
> their predators, but less problematic for small insectivorous and
> detritivorous mammals and birds. Acid rain may have been an important
agent
> of selective mortality and extinction across the Cretaceous-Tertiary
> boundary."
>