Laonastes aenigmamus

The Laotian rock rat (Laonastes aenigmamus) is a rodent found in the Khammouane region (Laos) and in the national park Phong Nha-Ke Bang, Quảng Bình Province, Vietnam. The species was brought to light in an April 18, 2005 article by Paulina Jenkins and colleagues, who considered it distinct enough from other rodents to place it into a new family, Laonastidae. The animals resemble large, dark rats with a thick, furry tail. Their skulls are very different and have features that set them apart from other rodents.

In 2006, paleontologists from the United States, France, and China published a study of Laonastes detailing a series of anatomical characters that relate it to the family Diatomyidae, in which it could soon be included (leaving Laonastidae, therefore, as a synonym of Diatomyidae).

Diatomyids are a family of rodents thought to have been extinct for 11 million years, known from Oligocene and Miocene fossils found in Pakistan, India, Thailand, China, and Japan. If it is confirmed that Laonastes aenigmamus is a living diatomoid, it is treated, like the monito del monte and the almiqui, as one of many examples of the lazarus effect (survival of a group considered extinct for millions of years because of a gap in the fossil record) that is detected in modern mammals.

A 2012 genetic study indicates that there are several lineages, some highly differentiated; it could be more than one species or subspecies.