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Re: mammal mystery




On Tue, 18 Feb 1997, Jeffrey Martz wrote:

>      Your idea assumes that dinosaurs did not evolve either.

Not at all.  It just states that they were structurally limited in their
reproductive mode to laying eggs which were easier to find than those laid
by smaller things.  And this factor became more important as they got
bigger (which they did over the cretaceous).

> It also
> forgets all the conservatively sized theropods like _Oviraptor_.  If I
> remeber right, most dinosaurs were "pony sized", and there were plenty 
> of small ones around that would be happy to much an unseuspecting
> mammal.  If you were a shrew sized mammal, would going after an egg so 
> large (considering the relative sizes of dinosaur eggs and most Cretaceous
> mammals) that you would have to eat it right there be worth the risk of
> ending up as a small theropod snack?

No, this is not my idea.  I say that dinosaurs, inasmuch as they lay eggs
that were relatively easy to find (relative, that is, to avian dinosaurs,
mammals, snakes, lizards,a nd turtles) _always_ suffered intense predation
on their eggs and offspring but that new species may have added to this
load.  I make the simple unfounded claim that some mammals and some birds
may have affected dinosaurs.  I am unsatisfied with purely environmental
"explanations" cause they don't explain.  We cannot know what did them in.
I argue for continuing research on K/T mammals, K/T birds, K/T speciation,
K/T everything including K/T bolides.  But I whine that the focus on
bolides seems to exclude all other possibilities.

>       Most importantly, you idea ignores the simultaneous extinctions
> of birds, mammals, and marine species.  Keep in mind that the bulk
> of studies of most mass extinctions, including the K-T extinction, are
> based on marine, not terrestrial species.

And so what do you do with Archibald's data based on terrestrial
organisms?  Ignore it?  He says that  northeastern
Montana species survival was as follows:
Placentals: 100 percent.
NA Dinos 0.000 percent.
I say this can be viewed independently of marine extinctions.  Not only
that, marine extinctions may not have been simultaneous as claimed.  Ward
says data on ammonites are consistent with either a sudden extinction _or_
a gradual one.  They _were_ in serious decline _before the K/T.  Nano
plankton are still disputed with some saying that the species that went
were not key species, that most successful ones survived.  Dinosaurs were
in decline before the K/T.  Pteros were almost gone, and on and on.  What
we are looking at is a very complex picture of SPECIATION which must have
had an effect on _itself_.   One might turn it around and call for answers
to this question: why were dinosaurs (apart from birds, alright) becoming
less diverse?  Why is this fact so often ignored when trying to explain
their ultimate lack of diversity-extinction?  Impactors try to counter
evidence of pulsed extinctions by invoking now multiple bolides.  Now we
are looking for Ockham.  It is all very unsettling, none of the pieces
fit.