Meeting Abstract

12.2  Monday, Jan. 4  The evolution of “endothermy”: terminological constraints and a phylogenetic analysis of metabolic rate evolution in non-mammalian therapsids BATAVIA, M.P.; University of California, Berkeley mbatavia@berkeley.edu

Numerous studies and reviews over the last several decades have addressed the evolution of endothermy in mammals (synapsids) and birds (diapsids). However, inconsistent usage of the term endothermy has hindered progress toward understanding the evolution of the complex suite of thermoregulatory and metabolic traits that characterizes these two clades of vertebrates. Furthermore, the term is often used to mean not only metabolically controlled thermoregulation, but also stable body temperature (homeothermy) and high metabolism (tachymetabolism). I propose that the evolution of metabolic rate (tachymetabolism versus bradymetabolism), stability of body temperature (homeothermy versus poikilothermy) and thermoregulatory mode (endothermy versus ectothermy) should be treated as potentially independent events. When broken down in this way, most work that has been done on the evolution of “endothermy” actually pertains to tachymetabolism only. A phylogenetic analysis of morphological traits associated with tachymetabolism indicates the possible acquisition of high metabolic rate early in therapsid evolution.