Respiration in pteros

[David Peters <davidpeters@att.net>]

I'm probably late with this, but Dr. Unwin's message was truncated on  
my copy. His header drew me to this website:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone. 
0004497

And this research article:

>>Respiratory Evolution Facilitated the Origin of Pterosaur Flight  
and Aerial Gigantism

Leon P. A. M. Claessens1*, Patrick M. O'Connor2, David M. Unwin3


Pterosaurs, enigmatic extinct Mesozoic reptiles, were the first  
vertebrates to achieve true flapping flight. Various lines of  
evidence provide strong support for highly efficient wing design,  
control, and flight capabilities. However, little is known of the  
pulmonary system that powered flight in pterosaurs. We investigated  
the structure and function of the pterosaurian breathing apparatus  
through a broad scale comparative study of respiratory structure and  
function in living and extinct archosaurs, using computer-assisted  
tomographic (CT) scanning of pterosaur and bird skeletal remains,  
cineradiographic (X-ray film) studies of the skeletal breathing pump  
in extant birds and alligators, and study of skeletal structure in  
historic fossil specimens. In this report we present various lines of  
skeletal evidence that indicate that pterosaurs had a highly  
effective flow-through respiratory system, capable of sustaining  
powered flight, predating the appearance of an analogous breathing  
system in birds by approximately seventy million years. Convergent  
evolution of gigantism in several Cretaceous pterosaur lineages was  
made possible through body density reduction by expansion of the  
pulmonary air sac system throughout the trunk and the distal limb  
girdle skeleton, highlighting the importance of respiratory  
adaptations in pterosaur evolution, and the dramatic effect of the  
release of physical constraints on morphological diversification and  
evolutionary radiation.<<




Good information to have, although much of this was touched on in  
1991 in Bennett's dissertation and subsequent paper on Pteranodon.  
Notably absent is any reference to the naris, which can be quite  
large in basal taxa, reaching an acme in Dimorphodon, followed by a  
reduction or confluence in later taxa. No reference to tracheal  
impressions, but then that would be a plesiomorphic character. Also  
absent: any reference to the extreme variation present in the  
prepubes, both in size and shape.

Be careful not to consider the pteroid position or the pedal bones of  
the Anhanguera reconstruction as gospel. I've never seen a reference  
to the prepubis in Anhanguera, so the one illustrated may be  
imaginary. In sister taxa the prepubis is extremely small, much  
smaller than the one illustrated.

Not sure about the mobility of the prepubis because the articulation  
with the pubis does not seem to support much movement in all taxa and  
indeed movement may be unnecessary according to the respiration  
offset illustrations supplied with the online article. The prepubis  
in the Rhamphorhynchus illustration is extremely small compared to  
the real deal. Might have been valuable to use a new illustration  
based on a fossil specimen, rather than a Wellnhofer drawing.

Congrats to all authors!

David Peters
davidpeters@att.net