Ailuravus is one of the earliest known rodents. Rodents are a group of placental mammals which first appeared within 10 million years after the extinction of the dinosaurs 65 million years ago. True mammals have existed for about 210 million years, but did not flourish until they could fill the vacant ecological niches left by the dinosaurs. The defining feature of a rodent is the large paired incisors that grow continuously throughout its life. These regenerating incisors have allowed various types of rodents to consume nearly any edible substance. Because of rodent's adaptability they have become the most successful and abundant group of mammals. The Messel quarry in Germany is world renowned for the near-perfect preservation of the fossils that it yields. For over 100 years the Messil site had been mined for its oil shale, or "brown coal" as it is commonly called. About 49 million years ago, during the Middle Eocene Epoch, the Messel area was a swampy fresh water lake environment with a rich and diverse flora and fauna. Seasonal blooms of algae in the Messel lakes would cause the water to be foul and stagnant. If an animal died and fell into the water, its carcass could lay unscavanged and undisturbed in the oxygen-depleted lake bottom. A fine mist of dead algae would cover the organism and preserve it in fine layers of shale. The result is unparalleled preservation of things seldom preserved such as fur, feathers, and gut contents Dimensions: 24-1/8" x 13" x 1"