Re: *Mauisaurus* vs large pterosaurs

[Tim Williams <tijawi@yahoo.com>]

Don Ohmes wrote:


> It is my opinion that the speculation that the long-necked
> plesiosaurs may have been adapted to be significant
> predators of marine volants generally, and large pterosaurs
> in particular, is justified. Even the relatively stiff neck
> would be advantageous. (Read "giant pterosaur-killing
> arrows"...)


I've never seen this particular idea, but I have heard a similar idea in 
"reverse".  I don't know if this idea ever appeared in print (i.e., in a 
published paper), but it's been suggested that the success of the Pterosauria 
drove the diversification of teleost fishes in the early Jurassic.  

Teleosts have a gas bladder, rather than lungs.  In this particular lineage of 
ray-finned fishes, the primordial lungs evolved into a gas bladder.  This 
allowed teleosts to be free of any connection with the surface.  The advantage 
of lungs is that it allows fishes to gulp air, and air is a richer source of 
oxygen than water.  Some extant non-teleost ray-finned fishes retain lungs, 
such as bichirs and garpikes.  

However, to gulp aerial oxygen, the fish has to come to the surface and pop its 
head above the water.  This left them vulnerable to sharp-eyed aerial 
pterosaurs.  So the success of pterosaurs favored the teleosts at the expense 
of the "lunged" ray-finned groups.  So runs this 'just-so' story, anyway.   

The extinction of pterosaurs provided no relief to air-gulping fishes, because 
by that time birds had radiated, and they were just as unforgiving.



Cheers

Tim