The world's oldest known mammal has been identified using dental records – predating what scientists previously thought was the first mammal to walk the Earth by millions of years – according to new research.
The Brasilodon was a tiny, "shrew-like" animal that measured almost 8 inches long.
Dental records for the mammal date back more than 225 million years – meaning the Barsilodon existed at the same time as some of the oldest dinosaurs, but 25 million years after the Permian-Triassic mass extinction, according to a Natural History Museum news release.
"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," Martha Richter, scientific associate at the museum .
"The evidence from how the dentition was built over developmental time is crucial and definitive to show that Brasilodons were mammals," Moya Meredith Smith,
professor at King’s College London stated. "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 previously known."
When analyzing three lower jaws of different growth stages in particular, the researchers concluded that the Brasilodon's first set of teeth (which started developing before birth) were later replaced with an "adult set."