Re: Cretaceous taeniodont

[John Bois <jbois@umd5.umd.edu>]

Thomas R. Holtz, Jr. wrote:
>>One thing that seems to be driving this assumption was that mammals were
in
>competition against dinosaurs BUT nothing else.

I am not making this assumption.  I am arguing, actually, that predation was
much more of a determinant of species success than competition--unless, that
is, you accept relative resistance against predation as an aspect of
competiton.

>>This doesn't accurately
>reflect the Mesozoic, particularly at the scale of mammals involved.  Other
>taxa need to be recognized here: sphenodontians (in the early Mesozoic),
>lizards (in the later Mesozoic), and various crocodyliforms throughout.
>Many of these may have been direct mammal competitors; others were
>potential
>predators.

Clearly, this is the crucible in which many subsequent winning traits were
forged: parental investment, sociality, perceptual acuity, homeothermy,etc.,
etc.

HP Williams said:
>...I think the reason this discussion has centered on
dinos-versus-mammals is because I have a suspicion that John Bois is using
the apparent size increase of Cretaceous mammals as an indicator for a
decline in dinosaur dominance.  (Am I right, John?  :-)  ).

Oh, I think dinosaurs would still be dominant (one could argue they are!) if
not for mammals.  I believe mammals and birds, today restrict the size and
niche breadth of all large egg-laying species.  Did they have an effect at
the K/T?  We'll see.  Was their size increase (if shown) an indicator of
dinosaur decline?  I don't know.  But, yes.  This is what I am arguing.

>In other words,
John is implying that mammals started getting bigger because the predatory
pressure from non-avian theropods was slackening off for some reason in the
Cretaceous.

Couldn't have said it better.