SCIENCE SNACK SCHEMA : SURVIVAL EVOLUTION

Like A Rat And Just As Durable : Snack size for a dinosaur, yet it thrived among them and then survived them.

AROUND 145 million years ago, the beach in what is today Dorset, England, was covered in a lagoon teeming with dinosaurs, pterosaurs, crocodiles and turtles. Making its way among all these beasts was a small puff of fur with excruciatingly sharp teeth.

Scientists last month described the prehistoric mammal in The Proceedings of the Geologists' Association. They named it Novaculadon mirabilis, from novacula, the Latin word for razor.

'' The premolars form quite a sharp cutting edge,'' said Steven Sweetman, a paleontologist in England and an author of the paper. The species was probably omnivorous, with teeth designed for processing vegetation but also possibly meat.

The mouse-size Novaculadon came from an order of mammals called multituberculates, named for the round ''tubercles,'' or outgrowths on their teeth.

They were among the most successful groups of ancient mammals yet discovered, living alongside dinosaurs during the Mesozoic Era. Though unrelated to mice and rats, they probably filled a similar role as a food source for larger predators while also dispersing seeds and controlling insects.

The Novaculadon specimen was found in a rock on the Dorset beach. Its full jawbone was found with the majority of its teeth intact, including a robust incisor and premolars, though it lacked the molars.

The fossil was so complete that researchers knew almost immediately they had found something new.  The jawbone was a part of the skeleton of an animal that most likely died nearby and hadn't been damaged in transport by rivers or other bodies of water.

The Novaculadon was probably doing things similar to the activities of the modern brown rat. The finding demonstrates how these mammals forged a niche that allowed for their survival well past the dinosaur age.

'' This wasn't some meek, pathetic creature - it was an animal that was well adapted to its particular lifestyle,'' said Steve Brusatte, a vertebrate paleontologist who was not involved in the study.

The World Students Society thanks Sara Novak.