Meeting Abstract

54.3  Thursday, Jan. 5  Breathing in a box: constraints on lung ventilation in giant pterosaurs GEIST, N.R.; HILLENIUS, W.J.*; FREY, E.; JONES, T.D.; ELGIN, R.A.; Sonoma State Univ.; College of Charleston; Staatl. Mus. Naturkunde Karlsruhe; Cal. State Univ. Stanislaus; Staatl. Mus. Naturkunde Karlsruhe

The evolution of large size among pterosaurs was usually accompanied by selection for a light yet strong skeleton, presumably to withstand the dynamic forces associated with flight, and most giant pterosaurs exhibit extensive fusion of the bones of the trunk. However, this process also added mechanical constraints on the mobility of the thorax that likely limited the options available for lung ventilation. Despite recent suggestions of an avian-like mechanism of costosternal pumping as the primary means of aspiration, an analysis of the lever systems associated with joints between the ribs, vertebrae, sternum, and pectoral girdle indicates limited mobility of the ribcage and sternum that is incompatible with that model. Rather, comparisons with modes of lung ventilation in extant amniotes suggests that the stiffened thorax, coupled with mobile gastralia and prepubic bones, was most consistent with an extra-costal mechanism for lung ventilation in large pterodactyloids, perhaps similar to a crocodile-like visceral displacement system