Mammals and birds today are warm-blooded, and this is often considered the reason for their great success.
University of Bristol paleontologist Professor Mike Benton identifies in the journal Gondwana Research that the ancestors of both mammals and birds became warm-blooded at the same time about 250 million years ago, at a time when life was recovering from the greatest mass extinction ever.
The Permian-Triassic mass extinction killed as much as 95 percent of life, and the very few survivors faced a turbulent world, repeatedly hit by global warming and ocean acidification crises. Two main groups of tetrapods survived, the synapsids and the arkosaurs, including ancestors of mammals and birds, respectively.
Paleontologists had identified indications of warm-bloodedness or technical endothermia in these Triassic survivors, including evidence of a membrane and possible whiskers in the synapses.
Recently, similar evidence for the early origin of the feather in dinosaurs and bird fathers has come to light. In both synapsids and archosaurs of the Triassic, the bone structure shows properties of warm-bloodedness. The evidence that mammalian ancestors had hair from the beginning of the Triassic has been suspected for a long time, but the suggestion that archosaurs had feathers from 250 million years ago is new.
But a strong hint of this sudden onset of warm-bloodedness in both synapsids and archosaurs at the exact time of the Permian-Triassic mass extinction was found in 2009. Tai Kubo, then a graduate student in paleobiology in Bristol, and Professor Benton identified that all medium-sized and large tetrapods shifted from scattered to upright posture just at the Permian-Triassic border.
Their study was based on petrified footprints. They looked at a sample of hundreds of fossil orbits, and Kubo and Benton were surprised to see the posture change instantly and not tense beyond tens of thousands of years, as had been suggested. It also happened in all groups, not just ancestors of mammals or ancestors of birds.
Professor Benton said: “Modern amphibians and reptiles are sprawlers that keep their limbs partially sideways.
“Birds and mammals have an upright position with the limbs immediately below their bodies. This allows them to run faster and especially longer. There are great benefits to upright posture and warm-bloodedness, but the price is that endotherms have to eat much more than cold-blooded animals. just to give their inner temperature control. “
The evidence of body modification and of early origin of hair and feathers, all at the same time, suggested that this was the beginning of a kind of ̵
Something like this happened in the Triassic 250 to 200 million years ago. Today, warm-blooded animals can live anywhere on earth, even in cold areas, and they remain active at night. They also show intensive parenting, feeding their babies and teaching them complex and smart behaviors. These adaptations gave birds and mammals the edge over amphibians and reptiles, and in the current cool world they allowed to dominate in several parts of the world.
Professor Benton added: “The Triassic was a remarkable time in the history of life on Earth. You see birds and mammals everywhere on land today, while amphibians and reptiles are often quite hidden.
“This revolution in ecosystems was triggered by the independent origin of endothermia in birds and mammals, but until recently we did not know that these two events might have been coordinated.
“It happened because only a small number of species survived the mass extinction of the Permian Triassic – which survived was dependent on intense competition in a harsh world. Because a few of the survivors were already endothermic in a primitive way, all the others had to become endothermic. to survive in the new fast-paced world. ”
More than 252 million years ago, mammalian fathers became warm-blooded to survive mass extinction
Michael J. Benton. The origin of endothermia in synapsids and arcosaurs and arms races in the Triassic, Gondwana Research (2020). DOI: 10.1016 / j.gr.2020.08.003
Provided by the University of Bristol
Citation: World’s Largest Mass Extinction Triggered Shift to Warmblood (2020, October 16) Retrieved October 16, 2020 from https://phys.org/news/2020-10-world-greatest-mass-extinction-triggered.html
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