Author:
Newham Elis,Gill Pamela G.,Brewer Philippa,Benton Michael J.,Fernandez Vincent,Gostling Neil J.,Haberthür David,Jernvall Jukka,Kankanpää Tuomas,Kallonen Aki,Navarro Charles,Pacureanu Alexandra,Zeller-Plumhoff Berit,Richards Kelly,Robson-Brown Kate,Schneider Philipp,Suhonen Heikki,Tafforeau Paul,Williams Katherine,Corfe Ian J.
Abstract
AbstractThere is uncertainty regarding the timing and fossil species in which mammalian endothermy arose, with few studies of stem-mammals on key aspects of endothermy such as basal or maximum metabolic rates, or placing them in the context of living vertebrate metabolic ranges. Synchrotron X-ray imaging of incremental tooth cementum shows two Early Jurassic stem-mammals,MorganucodonandKuehneotherium, had lifespans (a basal metabolic rate proxy) considerably longer than comparably sized living mammals, but similar to reptiles.Morganucodonalso had femoral blood flow rates (a maximum metabolic rate proxy) intermediate between living mammals and reptiles. This shows maximum metabolic rates increased evolutionarily before basal rates, and that contrary to previous suggestions of a Triassic origin, Early Jurassic stem-mammals lacked the endothermic metabolism of living mammals.One Sentence SummarySurprisingly long lifespans and low femoral blood flow suggest reptile-like physiology in key Early Jurassic stem-mammals.
Publisher
Cold Spring Harbor Laboratory