[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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.