Meeting Abstract
To understand the origin and evolution of the morphologically and functionally divergent avian and crocodylian respiratory systems, it is necessary to map out the bronchial architecture across the phylogenetic trees of these clades. The aim of this study is to describe the anatomy of the respiratory system of Cuvier’s dwarf caiman (Paleosuchus palpebrosus) based upon micro-computed tomography (uCT) data of the respiratory system in situ (n=4), and compare these data to other closely related archosaurian taxa. The lungs of four P. palpebrosus specimens were inflated artificially via a syringe, and imaged at total lung capacity. The following measures of the bronchial tree were acquired in the DICOM viewer OsiriX MD for intra- and interspecific comparisons: (1) the distance from the carina to the first three large secondary bronchi; (2) the area of the primary bronchus at the first three large secondary bronchi; and, (3) the area of the ostium of each of the first three large secondary bronchi where each one branches from the intrapulmonary primary bronchus. These data were then compared to the same quantitative measures acquired from the same homologous structures in Alligator mississippiensis (n=10), Crocodylus niloticus (n=3), Melanosuchus niger (n=1), and Caiman crocodylus (n=2), allowing for interspecific comparisons across Crocodylia. The basic anatomy of P. palpebrosus most closely resembles that of A. mississippiensis, with fewer large secondary airways and fewer small secondary saccular bronchi in the caudoventral regions of the lung than other crocodylians. These data also permit preliminary comparisons between the bronchial trees of birds and crocodylians so that hypotheses of homology, and initial reconstructions of the ancestral archosaurian bronchial tree may be made.
