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Re: Dinosaur egg-laying contributed to extinction?



> But dinosaurs, in particular huge dinosaurs, _didn't_ fare
> poorly except at the K-Pg boundary!
Well, I meant fared poorly *in that extinction*
Just do some handwaving that the other extinctions didn't reach a threshold 
severity, or make some other excuse, like dino's weren't as big in the 
triassic, and mammals weren't capable of competing with the dinos that survived 
the end of the Jurassic.

> Pretty much all those species died out that would be
> predicted to die out in an asteroid impact.
So then why would one predict Enantiornithines to die out? Is this a case of 
making predictions when you already know the outcome?

What prediction model would have Neoornithes and rodent-ike creatures survive, 
but something like Compsognathus (yes I know it wasn't around at the K-Pg 
boundary) die?

> *Confuciusornis* and the Enantiornithes, at a minimum, were
> apparently able to fly at a _very_ young age and did most of
> their growing later.

Well... this could then support the argument - those which had young which were 
on their own before becoming close to adult size, were more likely to go 
extinct. I'm not so sure about the premise that a difference between the size 
of an adult and the size of an independent-adolescent implies different 
ecological niches. It makes sense for large carnivorous, but I'm not so sure 
about grazing animals and insectivores.


> It was settled around 15 years ago. *Iberomesornis* is a
> juvenile, if that's what you're thinking about.

No, it was based on a quick wikipedia search, which lead to a citation from 
2002:
http://digitallibrary.amnh.org/dspace/bitstream/handle/2246/2876/N3387.pdf?sequence=1

Which seems to imply it was still an open question 10 years ago.


--- On Thu, 4/19/12, David Marjanovic <david.marjanovic@gmx.at> wrote:

> From: David Marjanovic <david.marjanovic@gmx.at>
> Subject: Re: Dinosaur egg-laying contributed to extinction?
> To: "DML" <dinosaur@usc.edu>
> Date: Thursday, April 19, 2012, 3:21 AM
> > > Also, many of the birds
> didn't survive either. We hear no more
 
> Or from any other birds other than Neornithes. That's why
> the youngest known bird tooth comes from the Maastrichtian
> of Maastricht.
> 
> >  And many mammal/cynodont lineages went extinct
> too, didn't they?
> 
> Not quite that many, but several did -- deltatheroidan and
> stagodontid metatherians for instance.
> 
> >  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.
> 
> That's all great, except...
> 
> >  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.
> 
> But dinosaurs, in particular huge dinosaurs, _didn't_ fare
> poorly except at the K-Pg boundary!
> 
> >  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.
> 
> And yet it did for 160 million years.
> 
> >  Still, it seems odd to me that more of the
> smaller dinos didn't live
> >  on, even if there were relatively few small
> species.
> 
> Pretty much all those species died out that would be
> predicted to die out in an asteroid impact.
> 
> >  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.
> 
> *Co
e Enantiornithes, at a minimum, were
> apparently able to fly at a _very_ young age and did most of
> their growing later.
> 
> >  By the way, is enantiornithine monophly settled,
> or is there still
> >  some doubt?
> 
> It was settled around 15 years ago. *Iberomesornis* is a
> juvenile, if that's what you're thinking about.
>