112-million-year old mammal jaw found in Japan

Japanese scientists have discovered the jaw of a 112-million-year old tiny primitive mammal from the early Cretaceous period.
The small creature, named Sasayamamylos kawaii belongs to an ancient group known as Eutherian mammals, which gave rise to all placental mammals.
Paleontologist Brian Davis of Missouri Southern State University said the jaw sports pointy, sharp teeth and molars in a proportion similar to that found in modern mammals, 'LiveScience' reported.
"This little critter, Sasayamamylos, is the oldest Eutherian mammal to demonstrate what paleontologists consider the modern dental formula in placental mammals," Davis said.
The latest mammal fossil suggests that these primitive creatures were already evolving quickly, with diverse traits emerging, at this point in the Cretaceous Era, he added.

Paleontologists recently proposed that the mother to all placental mammals lived about 65 million years ago, when dinosaurs went extinct.

The first true mammal likely emerged at least 100 million years before that, the report said.
Fossil-hunters were searching through sediments in Hyogo, Japan in 2007 when they unearthed the skeletal fragments of an ancient mammalian jaw.
The creatures jaw contained four sharp, pointy teeth known as pre-molars and three molars with complex ridges. That same pattern in the number of each type of tooth is found in placental mammals to this day, whereas earlier mammals have more of the sharp, pointy teeth.

The study was published in the journal Proceedings of the Royal Society B.