Re: Dinosaur egg-laying contributed to extinction?

[Erik Boehm <erikboehm07@yahoo.com>]

> Also, many of the birds didn't survive either.  We hear
> no more from
> the Enantiornithes after the Cretaceous.

And many mammal/cynodont lineages went extinct too, didn't they?
Anytime you have such a large disruption of the ecosystem, species will suffer.
I think the argument is basically that:
Large dinosaurs were more susceptible to ecological disruption - because, due 
to their large size, they had to pass through multiple ecological niches before 
reaching maturity. Sub-adults of large dino species filled niches for smaller 
animals, rather than a new smaller species.

One ecological niche becomes untenable, a species goes extinct. Other niches 
that the species filled go vacant, probably causing other extinctions in 
species that interacted with those now vacant niches.

I don't see this as an attempt to explain all the extinctions with a single 
criteria - instead they propose a reason why dinosaurs may have fared so poorly.

A general trend I see, is that those near the top of the food chain go extinct 
much more often. If dinos were species poor at smaller sizes, that wouldn't 
bode well for them.

Still, it seems odd to me that more of the smaller dinos didn't live on, even 
if there were relatively few small species.

I would be inclined to think it has something to do with parental care - and 
that birds out of necessity had to care for their young better than other 
dinos, as their young couldn't survive until they were able to fly.
By the way, is enantiornithine monophly settled, or is there still some doubt?

--- On Wed, 4/18/12, Tim Williams <tijawi@gmail.com> wrote:

> From: Tim Williams <tijawi@gmail.com>
> Subject: Re: Dinosaur egg-laying contributed to extinction?
> To: dinosaur@usc.edu
> Date: Wednesday, April 18, 2012, 11:28 PM
> Robert Schenck <schenck.rob@gmail.com>
> wrote:
> 
> 
> > Also, the authors, per the popular article anyway, say
> that the small
> > dinosaurs became birds. But this is only true for one
> small set of
> > dinosaurs, and many of the small dinosaurs in that set
> that did
Also, many of the birds didn't survive either.  We hear
> no more from
> the Enantiornithes after the Cretaceous.
> 
> 
> 
> 
> 
> 
> 
> Cheers
> 
> Tim
>