Re: Cretaceous taeniodont

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

On Thu, 8 Apr 2004, Tim Williams wrote:

> John Bois wrote:
>
> >I am arguing for the following scenario: predators of small mammals may
> >have been excluded from some habitats by predation on themselves.  _If_
> >bird species and pterosaurs were reduced by predatory birds--and I
> >believe the predation hypothesesis explains at least pterosaur dcline
> >better than competition--it is feasible that they could also threaten or
> >make life miserable for terrestrial (or arboreal?) dinosaurs.
>
> Not sure how/why predatory birds would have been even more of a threat to
> the survival of dinosaurs than the non-avian theropods already were.

Birds wack dino chicks on the fly, without needing to protect themselves.
Birds have better vantage for locating nests.  And, as you say, arboreal
nesting small dinosaurs would be at a real disadvantage.

> Still, all these factors must weighed
> against the fact that birds cannot get too big without losing the ability to
> fly.  Are you suggesting that this is why mammals got bigger in the
> Cretaceous, to better protect themselves against predatory birds?

Due to small size of dino babies, the limit to birds' size is not really a
factor in my view.  Re mammals vs. birds.  I'm sure there has/was always
been a risk to mammals from the air.  The question might be asked: how do
mammals today avoid excessive aerial predation; and what might it be in
small dinosaurs that did not allow similar protection?  I suspect this
gets down to the fundamental differences in reproductive mode.

> >If size gave immunity from predation, why didn't this fuel an arms race as
> >it seems to have done in dinosaurs.
>
> How do you know it didn't promote a mammal vs dino arms race?

Not sure what you mean, here?