nose, and very long whiskers. Their fur is dark slate grey, with a blackish tail. The belly is lighter, with a small, whitish area in the center. Their eyes are beady and black. They are about long with a tail and weigh about . Jenkins et al. (2004) described the jaw as hystricognathous, but Dawson et al. argued it is sciurognathous. The infraorbital foramen is enlarged, consistent with a hystricomorphous zygomasseteric system. The pterygoid fossae do not connect to the orbit, setting them apart from the hystricognathous rodents. Distribution The Laotian Rock rat is found in limestone karsts of Khammouan Province and southern Bolikhamxai Province, Laos, and also in a small area of Minh Hóa District, western Quảng Bình Province, Vietnam. In Vietnam, it is found in the 5 communes (xã) of Thượng Hoá, Hóa Sơn, Trung Hoá, Hóa Hợp, and Dân Hoá, and in Phong Nha – Kẻ Bàng National Park, near the villages of the Vietic-speaking Ruc, Sach, and Chut ethnic groups. It is also found directly across the border in Hin Namno National Biodiversity Conservation Area, Laos. In Laos, it is most common in the Phou Hin Poun National Biodiversity Conservation Area. Nguyen et al. suggested that the Quảng Bình and Phou Hin Poun populations may be distinct and genetically isolated from each other. Nicolas et al. found 8 major geographical clades and 8 to 16 evolutionary significant units among Laotian rock rat populations in Laos, and suggested that Laonastes may in fact consist of various undescribed cryptic species. Natural history Laotian rock rats are found in regions of karst limestone. They appear to be found only among limestone boulders on hillsides. Villagers in the area are familiar with the animal, calling it kha-nyou, and trapping it for food. The animals are presumed to be nocturnal. These rock rats appear to be predominantly herbivores, eating leaves, grass, and seeds. They may eat insects, as well, but probably not in high abundance. Females may give birth to a single young. Laotian rock rats appear to be quite docile and slow-moving over open ground. They walk with feet splayed outward in a gait described as duck-like. Although not ideal for mobility on open surfaces, this appears to be efficient when scrambling up and across large rocks. The sideways angle allows for greater surface area for their feet to find purchase on tilted or parallel surfaces. See also Living fossil