Little Bitty Ancient Mammal Unearthed in Japan

Tia Ghose, LiveScience Staff Writer

Date: 26 March 2013 Time: 08:01 PM ET

Paleontologists in Japan have unearthed the jaw of a primitive mammal from the early Cretaceous period.

The pint-size creature, named Sasayamamylos kawaii for the geologic formation in Japan where it was found, is about 112 million years old and belongs to an ancient clade known as Eutherian mammals, which gave rise to all placental mammals. (A clade is a group of animals that share uniquely evolved features and therefore a common ancestry.)

The jaw sports pointy, sharp teeth and molars in a proportion similar to that found in modern mammals, said paleontologist Brian Davis of Missouri Southern State University, who was not involved in the study.

"This little critter, Sasayamamylos, is the oldest Eutherian mammal to demonstrate what paleontologists consider the modern dental formula in placental mammals," Davis told LiveScience.

The new mammal fossil, described today (March 26) in the journal Proceedings of the Royal Society B, suggests that these primitive creatures were already evolving quickly, with diverse traits emerging, at this point in the Cretaceous Era, he added.

Continued:  http://www.livescience.com/28206-cretaceous-mammal-jaw-unearthed-japan.html