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The greatest mass extinction in the world has triggered a shift in hot blood

The greatest mass extinction in the world has triggered a shift in hot blood

Posture transition at the end of the Permian, 252 million years ago. Before the crisis, most reptiles had extensive posture; then they walked upwards. This may be the first sign of a new pace in Triassic life. Credit: animal drawings by Jim Robins, University of Bristol.

Mammals and birds today are warm-blooded, and this is often the cause of their great success.

University of Bristol palaeontologist Professor Mike Benton, is well known in the journal Gondwana Research that the ancestors of both mammals and birds became lukewarm at the same time, about 250 million years ago, at a time when life was recovering from the greatest mass extinction of all time.

The Permian-Triassic mass extinction has killed up to 95 percent of life, and very few survivors are facing a turbulent world, repeatedly hit by global warming and ocean acidification crises. Two major groups of tetrapods survived, the synapsids and archosaurs, including the ancestors of mammals and birds respectively.

Palaeontologists have identified indications of lukewarm blood, or technical endothermy, in Triassic survivors, including evidence for a diaphragm and possible whiskeys at synapsids.

Recently, similar evidence for the early origin of dinosaur feathers and bird ancestors has been shown. In both Triassic synapsids and archosaurs, bone structure reflects the characteristics of hot blood. Evidence that mammalian ancestors have had hair since the beginning of the Triassic has been suspected for a long time, but the suggestion that archosaurs had feathers from 250 million before the year.

But a strong indication for the sudden onset of hot blood in both synapsids and archosaurs at the exact time of the Permian-Triassic mass extinction was found in 2009. Tai Kubo, then a student studying Masters in Palaeobiology degree in Bristol and Professor Benton recognized that all medium-sized and large tetrapods moved from rotation to establish the posture itself on the Permian-Triassic border.

Their study is based on fossilized footprints. They looked at a sample of hundreds of fossil trackways, and Kubo and Benton were surprised to see the posture shift that occurred immediately, which had not been released in tens of millions of years, as suggested. This also happened to all groups, not just mother animal ancestors or bird ancestors.

Professor Benton said: “Modern amphibians and reptiles are sprawlers, holding their limbs slightly sideways.

“Birds and mammals have a good posture, with the extremities immediately beneath their bodies. They are allowed to run faster, and especially further. There are great advantages to erect posture and warmth. warm blood, but the cost is that endotherms need to eat more than animals with cold blood to boost their internal temperature control. “

Evidence from the change in posture and from the early origin of hair and fur, all happening at the same time, suggested that this was the beginning of a kind of ‘weapon race’. Ecologically, weapon races take place when predators and prey have to compete with each other, and where there may be increasing adaptations. The lion changes to run faster, but the wildebeest also evolves to run faster or twist and turn to escape.

Something similar happened in the Triassic, from 250 to 200 million years ago. Today, warm-blooded animals can live all over the Earth, even in cold places, and stay active at night. They also show intensive parental care, feed their babies and teach them complex and intelligent behaviors. These adaptations gave birds and mammals the edge of amphibians and reptiles and in the current cool world they are allowed to dominate more parts of the world.

Professor Benton added: “The Triassic is a remarkable time in the history of life on Earth. You can see birds and mammals everywhere on earth today, while amphibians and reptiles are often hidden.

“This revolution in ecosystems has been triggered by the independent source of endothermy in birds and mammals, but until recently we did not realize that these two events could be fixed.

“That happened because only a small number of species survived the Permian-Triassic extinction ̵

1; the survivors depended on intense competition in a tough world. Because some of the survivors were endothermic in a preliminary way, all others need to be endothermic to survive in the new fast-paced world. ”

More than 252 million years ago, mammal ancestors became warm-blooded to survive mass extinction.

Additional information:
Michael J. Benton. The origin of endothermy in synapsids and archosaurs and arm races in the Triassic, Gondwana Research (2020). DOI: 10.1016 / j.gr.2020.08.003

Provided by the University of Bristol

Citation: The greatest mass extinction in the world triggered a shift in blood heat (2020, October 16) obtained on October 16, 2020 from https://phys.org/news/2020-10-world-greatest- mass-extinction-triggered.html

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