The ancestors of both mammals and birds became warm-blooded at the same time, some 250 million years ago, at the time of the end of the Perm-mass extinction, according to new research from the University of Bristol.
The end-Permian extinction, also known as the Permian-Triassic extinction event and the Great Dying, was the worst mass extinction on Earth that ascended nearly 252.3 million years ago.
The catastrophe has killed nearly 96% of all marine species and 70% of terrestrial vertebrate species on the planet for thousands of years.
Sea water temperature calculations indicate that at the top of the extinction, the Earth is subjected to global warming, where the equatorial ocean temperature exceeds 40 degrees Celsius (104 degrees Fahrenheit).
Among the possible causes of this event, and one of the longest-assumed, is the massive burning charcoal that led to the catastrophic global warming, which is devastating to life.
Two major groups of tetrapods survived, the synapsids and archosaurs, including the ancestors of mammals and birds respectively.
Paleontologists have identified indications of warm-bloodedness (endothermy) in survivors of this Triassic, including evidence for a diaphragm and possible whiskeys in 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 long been suspected, but the suggestion that archosaurs had feathers from 250 million years ago is new.
But a strong indication for the sudden origin of hot blood in both synapsids and archosaurs at the exact time of the Permian-Triassic mass extinction was found in 2009.
In their research, University of Bristol Professor Mike Benton and Masters student Tai Kubo examined fossilized footprints and found that all medium-sized and large tetrapods moved from in the expansion to establish the posture itself on the Permian-Triassic border.
Paleontologists looked at a sample of hundreds of fossil trackways, and they were surprised to see the posture shift that took place immediately, unreleased for tens of millions of years, as suggested. This also happened to all groups, not just mother animal ancestors or bird ancestors.
“Modern amphibians and reptiles are sprawlers, holding their limbs slightly sideways,” Professor Benton said.
“Birds and mammals have good postures, with limbs just below their bodies. They are allowed to run faster, and especially.”
“There are great advantages to erect posture and warm blood, but the cost is that endotherms have to eat more than blood-bearing animals just to establish their internal temperature control. “
Evidence from the change in posture and from the early origin of hair and fur, all occurring at the same time, suggested that this was the beginning of a kind of ‘weapon race.’
“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,” Professor Benton said.
“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 have been coordinated.”
“That happened because only a small number of species survived the Permian-Triassic extinction – survivors depended on intense competition in a tough world.”
“Because some of the survivors are already endothermic in an initial way, everyone else needs to be endothermic to survive in the new fast-paced world.”
The study was published in the journal Gondwana Research.
Michael J. Benton et al. The origin of endothermy in synapsids and archosaurs and arm races in the Triassic. Gondwana Research, published online September 3, 2020; doi: 10.1016 / j.gr.2020.08.003