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Oxygen isotopes suggest elevated thermometabolism within multiple Permo-Triassic therapsid clades. | LitMetric

AI Article Synopsis

  • Birds and mammals are the only true endothermic vertebrates, capable of regulating their internal temperatures regardless of their environment.
  • The study examines the origins of mammalian thermoregulation by analyzing stable oxygen isotope compositions in therapsid fossils from the Permian and Triassic periods.
  • Findings suggest that certain therapsid groups independently developed elevated thermometabolism, with mammalian endothermy likely emerging in the Epicynodontia during the middle to late Permian, driven by significant climatic changes.

Article Abstract

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 (δO) of some of their Permo-Triassic therapsid relatives. Comparing of the δO 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.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5515572PMC
http://dx.doi.org/10.7554/eLife.28589DOI Listing

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