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Re: Copeing with mammals



And today's last...

----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Saturday, November 27, 2004 10:35 PM

Not in the least. In the first scenario, birds can actively push pterosaurs
out of ecological niches; in the second, they can only evolve into empty
niches.

OK...birds are better at evolving into empty niches. Why?

I was just speculating. I still think the simplest explanation for the extinction of the pterosaurs is the K-Pg boundary mass extinction. I just tried to explain that _if_ the long-term decline is real, it still doesn't automatically mean that competition took place.


With that kind of fossil record next to nothing can be said about this.

Still, we manage quite well.

Nobody but you has even tried for the last ten years or more.

Then why don't you take a look at precisely what those differences are, and
use that knowledge to _base_ a hypothesis of competition upon it?

With warmth and feathers, birds can persist in colder climates.

1. What colder climates?
2. Pterosaurs seem to have been just as endothermic as birds, and were insulated with that famous fur stuff.


Feathers are light, need less bone support, enable longer flight at less
energy expenditure.

I really don't think that feathers are lighter than a pterosaur wing membrane. And considering how exceedingly pneumatic the bones of large pterosaurs are, I can't imagine they had more bone support.


Parental care enables longer period of development, therefore more brain
development, therefore better processing of environmental info relating to
predators and or prey.

Evidence for the absence -- or any extent -- of parental care in LK pterosaurs?


Agility in flight allows a tighter turning circle, reverse of direction
for predator avoidance/prey capture

Evidence for greater agility of birds? (Bats are more agile than birds because they can change their wing shape.)


Nest building allows greater range of nesting habitats/concealment.

Which may or may not have been important. Besides, nothing is known about pterosaur nests.


Communication between group members is facilitated by bigger brains and
longer chick-rearing (e.g., learning the song).

Who says those particular birds (if they existed) were social? Who says altriciality -- a strategy that is derived _within_ Neornithes -- was an advantage in those particular ecological niches? Who says LK pterosaurs were not altricial?


Better sensory equipment allows for better prey capture/predator
avoidance.

Evidence for better sensory equipment in birds?

Oh, Geez.  It should be Eldridgian after Niles Eldridge, who said _all_
speciation follows catastrophies.

Did he? Or is this an overinterpretation of punctuated equilibrium?

----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Saturday, November 27, 2004 10:38 PM

High biodiversity is "the ghost of competition past".

This shouldn't be taken out of context. It refers to competition in today's ecosystem--_micro_evolution, if you will. It doesn't take into account massive influxes of new species, or massive new evolutionary developments. In these cases, the energy cost of taking over might entirely favor the usurper.

It's true that immigration is not taken into account. But an immigration is one event. I don't quite see how the resulting competition could last 40 million years ( ~ the time between the end of the K and the last diverse = Albian pterosaur assemblages).


The same goes for massive new evolutionary developments. Whatever the definition of "massive" is, either the birds made about one such development, say, every million years, or I have real trouble imagining 40 Ma of competition.