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Re: The birds vs. the pterosaurs

-----Original Message-----
From: Steve Doolittle <eustreptospondylus@usa.net>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Monday, February 05, 2001 12:58 PM
Subject: The birds vs. the pterosaurs


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

I`ve been taught in Ecology class, that the top of the food chain is most
sensitive to ecologic change, and they are usually large carnivores. The K-T
extinction, I believe, was unusual in that it effected the very base of the
foodchain, and in an extreme manner. I think that the blocking of
photosynthesis was the KEY factor. (everything else, from high winds to
climate change was insignificant in comparison). All green vegetation was
wiped out for a period of (probably) a couple of months....(later, seeds
could germinate and sprout new life). This left as a food source, dead plant
matter, (and buried roots).  Most likely, all vegetarians dependant on
greens died off, (both large and small). Insects survived in large number,
cause they could feed off the dead vegetation. Small  warm-blooded
insectivores survived in limited numbers. Cold blooded carnivores of
somewhat larger size could have survived on less frequent feedings.

Most likely, all post Cretaceous mammals and birds evolved from surviving
insectivores. As for pterosaurs, by the end of the cretaceous, the only
existing ones were large, fish eating species, near the top of the food
chain, and thus hit very hard. Many birds were probably insectivorous during
the cretaceous, utilizing bills for the extraction of insects from bark, and
not needing teeth for their insect eating habit. Insect eating pterosaurs
were probably outcompeted by these birds long before the end of the
cretaceous.Believing in BCF, therefore, no new theropods with teeth were
able to evolve from this basic bird stock, hence, no new big carnivorous
dinosaurs (with teeth), and the vegetarian dinosaur stock was also wiped out
(both large and small), so, ...no new large vegetarian dinosaurs.

Disclaimer,...I wasn`t there to see all this, but it seems (to me) the most
likely scenario that covers what survived the K-T impact, and what did not.