title: Implications of an avian-style respiratory system for gigantism in sauropod dinosaurs.
abstract: In light of evidence for avian-like lungs in saurischian dinosaurs, the physiological implications of cross-current gas exchange and voluminous, highly heterogeneous lungs for sauropod gigantism are critically examined. At 12 ton the predicted body temperature and metabolic rate of a growing sauropod would be similar to that of a bird scaled to the same body weight, but would increase exponentially as body mass increases. Although avian-like lung structure would be consistent with either a tachymetabolic-endothermic or a bradymetabolic-gigantothermic model, increasing body temperature requires adjustments to avoid overheating. We suggest that a unique sauropod structure/function unit facilitated the evolution of gigantism. This unit consisted of (1) a reduction in metabolic rate below that predicted by the body temperature, akin to thermal adaptation as seen in extant squamates, (2) presence of air-filled diverticula in the long neck and in the visceral cavity, and (3) low activity of respiratory muscles coupled with the high efficiency of cross-current gas exchange.
authors.affiliation: Institut für Zoologie, University of Bonn, Bonn, Germany. perry@uni-bonn.de
authors.forename: Steven F
authors.initials: SF
authors.lastname: Perry
authors.forename: Andreas
authors.initials: A
authors.lastname: Christian
authors.forename: Thomas
authors.initials: T
authors.lastname: Breuer
authors.forename: Nadine
authors.initials: N
authors.lastname: Pajor
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Codd
mesh_terms: D000818:Animals; D001831:Body Temperature; D025061:Dinosaurs / Q000033:anatomy & histology*; D012137:Respiratory System / Q000033:anatomy & histology*