A Mammal-Like Reptile Shared Time And Space With Ancient Mammals

There is one mammal-like reptile that might have lived through longer years than thought. Scientists found that tritylodontids, which was the last-known family of reptiles that looked almost like mammals, might have lived with some of the species before creatures who had features such as advanced hearing evolved.

These creatures provide the missing links in the development of mammals from reptiles.

"Tritylodontids were herbivores with unique sets of teeth which intersect when they bite," said Hiroshige Matsuoka of Kyoto University, one of the researchers involved in the latest study. "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."

The creatures of the Jurassic era existed all over the world, but soon got overtaken by herbivorous mammals and died out, not competing for the same space or resources.

However, they may have been alive 30 million years longer than scientists had first assumed.

Discovering 250 tritylodontid teeth found first in Japan, scientists were clear that the species might have existed at the same time as the first mammals.

"Usually, fossils are identified as a new species only when a relatively complete set of structures like a jaw bone are found," Matsuoka said. "In these cases, characteristics of teeth tend to be described only briefly. Tritylodontid teeth have three rows of 2 to 3 cusps. This time, we paid attention to fine details like the size and shape of each cusp. By using this method, it should be possible to characterize other species on the evolutionary tree as well. Because fossils of so many diverse families of animals are to be found in Kuwajima, we'd like to keep investigating the site to uncover things not just about individual species, but also about entire ecological dynamics."

The findings were published in the April edition of the Journal of Vertebrate Paleontology.