[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Dinosaur egg-laying contributed to extinction?



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

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.

*Confuciusornis* and the 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.