The world’s oldest mammal, resembling a shrew, has been identified from fossilized teeth. The animal lived about 225 million years ago, which is about 20 million years earlier than the previously confirmed oldest mammal. The new discovery is labeled “very important” by the researchers.

    Brasilodon quadrangularis was a small shrew-like animal about 20 centimeters long. The animal roamed the earth about 225 million years ago, at the same time as some of the oldest dinosaurs. 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 evidence from fossils of hard tissues such as bones and teeth. The glands of mammals, which produce milk, have not been preserved in any fossil found to date.

    Until now, the Morganucodon was considered the first mammal, with isolated teeth found to be 205 million years old. The Morganucodon had a small body and a long face, similar to that of shrews or civets.

    The dental records in the published study date Brasilodon quadrangularis to 225 million years ago. that’s 25 million years after the Permian Triassic mass extinction, the third and largest mass extinction, when more than 90 percent of species disappeared into the ocean and 70 percent of terrestrial animals became extinct.

    Classified wrong

    Martha Richter, a research associate at the museum and lead author of the article, told CNN that the Brasilodon quadrangularis was previously considered an “advanced reptile,” but examination of its teeth “conclusively” shows that it was a mammal.

    “If you think of reptiles, they have many different replacement teeth over their lifetime, but we mammals only have two. First the baby teeth and then the second set that replaces the original set. This is what characterizes mammals,” says Richter.

    Richter and her colleagues examined three mandibles of the species, which lived in the area that now occupies the southernmost part of Brazil. “This was a very small mammal that was probably a burrowing animal that lived in the shadow of the oldest known dinosaurs from that period,” Richter said.

    Her team worked on the project for more than five years and describe their discovery as “very important”. In the news release, Richter says the findings have contributed “to our understanding of the ecological landscape of this period and the evolution of modern mammals.”