A mammal-like reptile may have survived a lot longer than previously thought. Scientists found that tritylodontids, the last-known family of near-mammalian reptiles, may have coexisted with some of the earliest mammal species (before those with features such as advanced hearing evolved). More specifically, these creatures actually link the evolution 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."
Tritylodontids lived in the Jurassic era and proliferated worldwide, but were thought to have died out as herbivorous mammals took over. This, in particular, made sense to scientists. Otherwise, the species would have competed for the same particular niche and the same resources.
With that said, researchers have now found that these animals may have survived about 30 million years longer than scientists first thought.
The researchers discovered 250 tritylodontid teeth, which were the first to be found in Japan. More specifically, these teeth showed that the species may have been around at the same time as the very 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 reveal a bit more about these animals and also show that they were around for a lot longer than previously thought.
The findings were published in the April edition of the Journal of Vertebrate Paleontology.