Univ Lyon, Université Lyon 1, Ens de Lyon, CNRS, UMR 5276 LGL-TPE, Villeurbanne, France, France; Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
Romain Amiot
Univ Lyon, Université Lyon 1, Ens de Lyon, CNRS, UMR 5276 LGL-TPE, Villeurbanne, France, France
François Fourel
Univ Lyon, Université Lyon 1, Ens de Lyon, CNRS, UMR 5276 LGL-TPE, Villeurbanne, France, France; Univ Lyon, Université Lyon 1, CNRS, UMR 5023 LEHNA, Villeurbanne, France, France
Fernando Abdala
Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
Frédéric Fluteau
Institut de Physique du Globe de Paris, Paris, France
Nour-Eddine Jalil
Centre de Recherches en Paléobiodiversité et Paléoenvironnements, UMR 7207 CNRS-MNHN-UPMC, Museum National d’Histoire Naturelle, Paris, France
Jun Liu
Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
Bruce S Rubidge
Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
Roger MH Smith
Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa; Iziko South African Museum, Cape Town, South Africa
J Sébastien Steyer
Centre de Recherches en Paléobiodiversité et Paléoenvironnements, UMR 7207 CNRS-MNHN-UPMC, Museum National d’Histoire Naturelle, Paris, France
Pia A Viglietti
Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
Xu Wang
Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
Christophe Lécuyer
Univ Lyon, Université Lyon 1, Ens de Lyon, CNRS, UMR 5276 LGL-TPE, Villeurbanne, France, France; Institut Universitaire de France, Paris, France
The only true living endothermic vertebrates are birds and mammals, which produce and regulate their internal temperature quite independently from their surroundings. For mammal ancestors, anatomical clues suggest that endothermy originated during the Permian or Triassic. Here we investigate the origin of mammalian thermoregulation by analysing apatite stable oxygen isotope compositions (δ18Op) of some of their Permo-Triassic therapsid relatives. Comparing of the δ18Op values of therapsid bone and tooth apatites to those of co-existing non-therapsid tetrapods, demonstrates different body temperatures and thermoregulatory strategies. It is proposed that cynodonts and dicynodonts independently acquired constant elevated thermometabolism, respectively within the Eucynodontia and Lystrosauridae + Kannemeyeriiformes clades. We conclude that mammalian endothermy originated in the Epicynodontia during the middle-late Permian. Major global climatic and environmental fluctuations were the most likely selective pressures on the success of such elevated thermometabolism.
