A 225 million-year-old mammal is the oldest ever

Brasilodon quadrangularis was a small, shrew-like creature about 20 cm long that walked the earth 225 million years ago. According to a team of Brazilian and British scientists, it coincides with some of the oldest dinosaurs and sheds light on the evolution of modern mammals.

The discovery was made by researchers from the Natural History Museum in London, King’s College London and the Federal University of Rio Grande do Sul in Porto Alegre.

Scientists relied on evidence provided by fossils of hard tissues such as bones and teeth. Because the glands of milk-producing mammals have not been preserved in any fossil found so far.

To date, Morganucodon is believed to be the first mammal whose isolated teeth show it is about 205 million years old. Morganucodon had a small jerboa-like body and a long face resembling a shrew or civet cat.

Dental records in the study, published Tuesday in the Journal of Anatomy Square, date Brazil to 225 million years — 25 million years after the Permian-Triassic mass extinction — The third and largest mass extinction, when more than 90% of species in the ocean disappeared and 70% of land animals died.

wrong identity

Martha Richter, a research fellow at the museum and lead author of the paper, told CNN that Brazil was previously thought to be an “advanced reptile,” but examination of its teeth “conclusively” shows it is a mammal.

“If you think of reptiles, they have many, many replacement teeth throughout their lives, but we mammals only have two. First the milk teeth, then the second teeth that replace the original set of teeth. This is what distinguishes mammals,” says Richter. .

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The press release said that prazilodon is the oldest extinct vertebrate with consecutive teeth – milk teeth and one permanent set – also known as diviodonts.

The first group begins to develop during the embryonic stage and the second group develops after birth.

Richter and her colleagues studied three mandibles from species that inhabit the now surveyed area of ​​southern Brazil. Under a microscope, she said, they discovered “the type of dentures found only in mammals.”

“This was a very, very small mammal that was probably a burrowing animal that lived in the shadow of the oldest dinosaurs that we know from that time,” Richter added.

She said the team had been working on the project for more than five years and described their discovery as “extremely significant”.

The findings “added to our understanding of the ecological landscapes of the time and the evolution of modern mammals,” Richter said in a press release.

Moya Meredith Smith, contributing author and professor of structural biology of evolutionary teeth at Kings College London, said in the statement: “Our article increases the debate about what is known as mammals and shows that it is a much older fossil record than previously known.” “

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