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

Respiration in pteros

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