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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.