Teeth can be great storytellers. For example, they can tell of near-mammalian reptiles that may have lived way longer than previously believed.
The Mesozoic Era was called the Age of Reptiles for a reason: it was the time when dinosaurs and other forms of reptiles emerged. However, it also marked the birth of mammals. Thus, it wasn't so surprising to come across tritylodontids.
Tritylodontids are a family of near-mammalian reptiles. "They had pretty much the same features as mammals – for instance they were most likely warm-blooded – but taxonomically speaking they were reptiles, because in their jaws they still had a bone that in mammals is used for hearing," said Hiroshige Matsuoka, study author from Kyoto University.
The herbivorous family flourished during the Jurassic Period and is believed to have reached almost all corners of the world including Antarctica. But before the period was over, they had gone extinct, believed to have been taken over by mammals that also fed on plants.
Such belief, however, is now challenged with the discovery of 250 fossilized teeth belonging to a new species of tritylodontids.
The set of teeth came along with other fossils of mammals, other types of reptiles, and plants that date back to the Cretaceous Period, which came right after the Jurassic Period.
This then suggests that tritylodontids may have actually lived about 30 million years longer than what was commonly thought. Not only that, but they may have co-existed with mammals, which were partly blamed for their complete disappearance.
As to how the paleontologists identified the new species belonging to the genus now called Montirictus kuwajimaensis, they took a more novel approach: they based it on the teeth themselves.
This family of reptiles possessed a unique set of teeth. By counting the number of cusps and paying more attention to their size and shape, they were able to describe M. kuwajimaensis.
"[It] is a medium-sized tritylodontid genus characterized by upper cheek teeth having the cusp formula 2-2-2 with subequal cusps, buccal and lingual cusps retaining a crescentic shape with both buccal and lingual ridges anteriorly, and 'V'-shaped buccolingual cross-sections of two anteroposterior grooves between the three cusp rows," said the study now in Journal of Vertebrate Paleontology.
While this discovery provides new learning to the world of paleontology, the researchers want to widen their scope, such as knowing the "ecological dynamics" of the time these species lived.