Aspiration Pump

Another characteristic shared by pterosaurs and birds:
http://www.ploscollections.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0004497;jsessionid=A1CA60013B42AE8DCA4EDCACEF3A2BF7
"The aspiration pump of pterosaurs maximised trunk expansion in the ventrocaudal region, while at the same time limiting the degrees of freedom of movement of the trunk in other directions. This provided greater control over the location, amount and timing of trunk expansion, thereby enabling precisely-timed localized generation of pressure gradients within the pulmonary system, a trait that is also present in living birds where it is of paramount importance for the generation of air flow patterns in the lungs [27], [36]." (Leon P. A. M. Claessens^1*, Patrick M. O'Connor², David M. Unwin³⁾