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re: hybodonts at K/T correction
Not only is it possible that the hybodonts went through the K/T transition
unaffected, a great many dinosaurs survived (namely birds). Actually, this
is my first post and I'm not sure how in-depth ya'll have discussed the K/T
boundary. Forgive me if I go over old territory.
First, in the paleontological world the importance of the "K/T boundary"
is in dispute. We only have a snapshot of mesozoic and tertiary life. We
should not be surprised that no species of "dinosaurs" (the big lizard)
survived more than a few million years. Only one species has been found in
more than one stratigraphic layer (species, not taxon). The K/T " die out
may just be representative of changing conditions world wide, and not be the
result of some global catastrophe.
Second, by the systematics used in paleontology now, birds are dinosaurs.
And Aves (or birds) had evolved by the late Cretaceous. So why didn't they
die out with the other dinosaurs?
Third, we only know about 500 dinosaur species (correct it, but I think
I'm in the ballpark) all thinly spread out through 100-150 million years. I
do not think that we have anywhere near a reasonable picture of the
diversity of life in the past. We have enough of the puzzle to learn a lot
about vertebrate development, but not nearly enough to construct scenarios
on mass extinction. Even the mass extinctions took millions of years to
happen. Hardly a stunning and instantaneous loss.
Finally, I only raise these points because I've seen it from both sides.
In a Bio class, I had to present a synopsis of some articles discussing how
the meteor-of-doom theory worked. And in a Geo class on dinosaurs, I have
read articles refuting the plausibility (sp?) of the mass extinction theory.
Just some random thoughts from the middle of Texas,
University of Texas, Austin