Washington: Paleontologists have affirmed the idea that mammals, an extremely diverse group that includes egg-laying monotremes, originated at least 208 million years ago, much earlier than some previous works of research suggest.
This was confirmed after the discovery of three new small squirrel-like species in China.
The three new species - Shenshou lui, Xianshou linglong, and Xianshou songae - are described from six nearly complete 160-million-year-old fossils found in China.
The animals have been placed in a new group called Euharamiyida and had tails and feet that indicate that they were tree dwellers.
"They were good climbers and probably spent more time in trees than squirrels," said Jin Meng, co-author and curator in the American Museum of Natural History division of paleontology.
The discovery is significant as it places a poorly-understood Mesozoic group of animals firmly in the mammal family tree.
The study, led by scientists from the American Museum of Natural History and the Chinese Academy of Sciences, corroborates the idea that mammals originated at least 208 million years ago in the late Triassic.
"The new specimens we discovered are extremely well preserved. And based on these fossils, we now have a good idea of what these animals really looked like. Confirming that they are, indeed, mammals," concluded Meng.
The study appeared in the journal Nature.