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