Man’s earliest known mammal ancestor has been uncovered thanks to its teeth.
The species, Brasilodon quadrangularis, predates the previously oldest known mammal by 20 million years, according to scientists.
Its dental records — so to speak — date back to 225 million years ago in the late Triassic period, meaning the creature coexisted with some of the oldest known dinosaur species.
The findings were published in a paper in the Journal of Anatomy on Monday.
“Dated at 225.42 million years old, this is the oldest known mammal in the fossil record contributing to our understanding of the ecological landscape of this period and the evolution of modern mammals,” the paper’s lead author, Martha Richter, said in a statement from Britain’s Museum of Natural History.
Brasilodon was a shrew-like creature, almost eight inches long and possessing two sets of teeth — an original and a spare.
That trait is common to most current mammal species. Scientists cannot look for mammary glands in fossils, since soft tissue is rarely preserved, leaving them to examine mineralized teeth instead.
The process of tooth replacement “involves profound, time-controlled changes to the skull anatomy, for instance the closure of the secondary palate (the roof of the mouth) that allows the young to suckle, while breathing at the same time,” according to Britain’s Museum of Natural History.
Tooth replacement has also been linked to being warm-blooded, as mammals are, and the development of fur.
Like modern rodents, Brasilodon is thought to have been a burrowing animal.
“This was a very, very small mammal that was probably a burrowing animal living in the shadows of the oldest dinosaurs that we know from that period,” Ms. Richter told CNN.
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