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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 ;-).

T. Yazbeck

----- Original Message -----
From: "David Marjanovic" <david.marjanovic@gmx.at>
To: dinosaur@usc.edu
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.