On Sat, 18 Nov 2000, Ken Kinman wrote:
> I was a little surprised by Mike's numbers. The Late Jurassic numbers
> were higher than I would have guessed, and even the Late Triassic numbers
> are very good.
Just out of curiosity, what would you have expected?
> Looks like the dinosaurologists are doing a pretty good job of finding
> these older dinosaurs (and kin). It certainly seems like Ornithodira
> established their success relatively quickly, and thenceforth displayed what
> one might expect----a relatively stable succession of faunas gradually
> replacing one another throughout the Jurassic and Cretaceous.
Well, there is one big exception (even more apparent looking at the genera
per mega annum figures) -- by the end of the Jurassic, diversity is at its
highest yet. Then, as the Cretaceous starts, it drops to extremely low
levels (before building up even higher than before by the end of the
Cretaceous), indicating a mass J/K extinction (or a paucity of Neocomian
deposits?).
> Are there any figures on the breakdown of genera (or species) numbers
> for the Maastrichtian in particular. Is it pretty steady throughout this
> last period of dinosaur evolution until the sudden extinction at the end?
If I'm not mistaken, the only known fossil-bearing deposits that go right
up to the end are in North America -- I don't know if the fossil record is
good enough to say exactly what was going on world-wide.
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