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Re: Mesozoic birds made insects shrink
You're right about the metabolic rate idea, and on the anurognathids as well. I
meant to say that they were not as efficient as birds, not that they were
flying lizards. I don't know anything about the pterosaurian respiratory
system, so I trust you're right about that. What about the intelligence of the
pterosaurs? I wonder if birds were smarter or (more alert visually), possibly
being able to catch insects better than their pterosaurian rivals. And weren't
pterosaurs bad at taking off/landing? Imagine a grounded pterosaur attacked by
a flock of birds in a rainstorm. Ever see a hawk harassed by finches? With
their thicker integument, I would venture to say that birds were able to
survive in colder regions than pterosuars could. And as far as I know,
Pterosauria can only belong to one class: Reptilia. I am aware of the idea that
dinosaurs were just as endothermic as mammals and birds, so don't bring
classification into the fray ;-).
----- Original Message -----
From: "David Marjanovic" <email@example.com>
Sent: Tuesday, June 5, 2012 2:51:13 PM
Subject: Re: Mesozoic birds made insects shrink
> Yet the smaller rhamphorhynchoids of the Triassic and Jurassic had
> mostly died off by the Cretaceous,
*Rhamphorhynchus* and *Scaphognathus* were _not_ small.
The anurognathids were small, and they were diverse in the Early Cretaceous
(or, at least, we have a fossil record of them!). But they were specialized.
> because of the more active lifestyle (endothermy) of the birds, or their
> efficient respiratory (air sac?) system; both factors would give Aves an
> advantage over the more reptilian physiology of pterosaurs.
And what makes you think that pterosaurs had a "reptilian physiology"? :-)
Perhaps the fact that they used to be classified as reptiles? That only means
they're amniotes but weren't classified as birds or mammals; it doesn't tell
you anything else.
There's lots of evidence from pneumatic bones that pterosaurs had a bird-style
respiratory system; their "fur" (pycnofibers) must have impeded the free
exchange of heat; and it's quite doubtful whether a bradymetabolic flying
vertebrate is even possible.