title: Dinosaur physiology. Evidence for mesothermy in dinosaurs.
abstract: Were dinosaurs ectotherms or fast-metabolizing endotherms whose activities were unconstrained by temperature? To date, some of the strongest evidence for endothermy comes from the rapid growth rates derived from the analysis of fossil bones. However, these studies are constrained by a lack of comparative data and an appropriate energetic framework. Here we compile data on ontogenetic growth for extant and fossil vertebrates, including all major dinosaur clades. Using a metabolic scaling approach, we find that growth and metabolic rates follow theoretical predictions across clades, although some groups deviate. Moreover, when the effects of size and temperature are considered, dinosaur metabolic rates were intermediate to those of endotherms and ectotherms and closest to those of extant mesotherms. Our results suggest that the modern dichotomy of endothermic versus ectothermic is overly simplistic.
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA. jgrady@unm.edu.
authors.forename: John M
authors.initials: JM
authors.lastname: Grady
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA. The Santa Fe Institute, USA, 1399 Hyde Park Road, Santa Fe, NM 87501, USA.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Enquist
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Eva
authors.initials: E
authors.lastname: Dettweiler-Robinson
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Natalie A
authors.initials: NA
authors.lastname: Wright
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Felisa A
authors.initials: FA
authors.lastname: Smith
mesh_terms: D000818:Animals; D001831:Body Temperature; D025061:Dinosaurs / Q000145:classification / Q000254:growth & development* / Q000378:metabolism*; D004734:Energy Metabolism; D005580:Fossils; D010802:Phylogeny