A shrew-like creature that lived 225 million years ago is the oldest mammal identified so far

See what the oldest mammal ever identified looked like 0:40 London (CNN) — The world’s oldest mammal — predating the previously confirmed oldest mammal by some 20 million years — has been identified using fossil dental records, in a new discovery hailed as “highly significant” by the researchers. Brasilodon quadrangularis was a small shrew-like creature, about 20 centimeters long, that walked the earth 225 million years ago at the same time as some of the oldest dinosaurs, and its identification sheds light on the evolution of modern mammals. , according to a team of Brazilian and British scientists. 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. The scientists relied on clues provided by fossils of hard tissues like bones and teeth. This is because mammalian glands, which produce milk, have not been preserved in any fossil found to date. Until now, Morganucodon had been considered the first mammal, with isolated teeth showing that it dates back around 205 million years. Morganucodon had a small gerbil-like body and an elongated face similar to those of shrews or civets. Dental records from the study published Tuesday in the Journal of Anatomy date Brasilodon quadrangularis to 225 million years ago—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 became extinct. Mistaken identity Martha Richter, an associate scientist at the museum and the article’s lead author, told CNN that Brasilodon quadrangularis was previously believed to be an “advanced reptile,” but examination of its teeth shows “definitely” that it was a mammal. “If you think about reptiles, they have many, many different replacement teeth throughout their lives, but we mammals only have two. First, the milk teeth, and then the second dentition that replaces the original set. Here’s what defines mammals,” Richter said. Brasilodon is the oldest extinct vertebrate with two sets of successive teeth, milk teeth, and a permanent set, also known as diphydontia, according to the news release. The first set begins to develop during the embryonic stage and the second set develops after birth. Richter and her colleagues examined three lower jaws of the species, which lived in the region that today covers the southernmost section of Brazil. Under the microscope they discovered “the kind of replacement teeth that are only present in mammals,” she said. Richter added: “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 of from that period.” She said the team had been working on the project for more than five years and described their discovery as “very significant”. In the news release, Richter said the findings added “to our understanding of the ecological landscape of this period and the evolution of modern mammals.” Moya Meredith Smith, a contributing author and professor of evolutionary dentoskeletal biology at King’s College London, said in the statement: “Our paper raises the level of debate about what defines a mammal and shows that it was a much earlier time of origin. in the fossil record than was previously known.