(Laonastes aenigmamus)
The kha-nyou was discovered by scientists visiting a market in Lao PDR in 2005. It was subsequently shown to be a living fossil – the sole surviving member of an ancient group of rodents that was previously considered to have gone extinct some 11 million years ago. The kha-nyou is extremely distinct from all other mammal species, having separated from its closest living relatives, the gundis of Africa, 44 million years ago. It resembles a cross between a squirrel and a large rat, with its elongated head, small, rounded ears and bushy tail. Known only from an area of limestone karst in Khammouan Province in Lao PDR, the species is thought to be under pressure from hunting practices and possibly habitat degradation resulting from logging and the collection of firewood.
Urgent Conservation Actions
Further research into the conservation status and threats facing the kha-nyou is urgently needed.
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Evolutionary Distinctiveness
Order: Rodentia
Family: Diatomyidae
The kha-nyou was first described in 2005, after specimens purchased by scientists visiting a local food market in Lao were shown to be unique. It was subsequently shown to be the sole surviving member of the ancient and morphologically distinct rodent family Diatomyidae. Species in this family were thought to have lived from 33.9 Mya (Early Oligocene) to 11.6 Mya (Late Miocene), and, until the discovery of the kha-nyou, to have been extinct for 11 million years. The discovery of living examples of taxa that were previously thought to be extinct is a very special case of the “Lazarus effect”, one that has only rarely been documented among mammals and other vertebrates.

Molecular studies have revealed that the kha-nyou’s closest living relatives are the five surviving species of gundi (family Ctenodactylidae), all of which are currently confined to Africa. However, these two families diverged around 44 million years ago, making Laonastes the sole representative of 44 million years of unique evolutionary history.
Head and body length: 212 – 285mm
Weight: 0.3 - 0.45 kg
Kha-nyou are squirrel-like in appearance, with an elongated head, small rounded ears and a long bushy tail. The compact body is covered in long, soft, dense fur that varies in colour from dark grey to black. Individuals have padded feet to provide grip on steep rocky slopes and long whiskers that act as a sensory aid to movement in rock crevices.
L. aenigmamus is believed to be nocturnal. The structure of the teeth together with analysis of stomach contents from two specimens indicates the species has a primarily vegetarian diet, consisting of leaves, grass and seeds and possibly the occasional insect. Females are thought to give birth to a single young.
Individuals have been found in areas with large limestone boulders, on steep slopes surrounding karst formations. Slopes in these areas are covered in both evergreen and deciduous trees, but have little ground vegetation.

The kha-nyou is known only from Khammouan Province in Lao People’s Democratic Republic (PDR). It is thought to be largely confined to the Phou Hin Poun National Biodiversity Conservation Area (formerly known as Khammouane Limestone National Biodiversity Conservation Area). The majority of specimens were collected in the vicinity of Ban Mauang and Ban Doy villages in Thakhek District. 

Population Estimate
Population Trend
Classified as Endangered (EN B1ab (ii, iii, v)) on the 2010 IUCN Red List of Threatened Species.
The limestone karst in which the species is found is fairly resilient to degradation. However, more accessible areas of the karst are vulnerable to logging and firewood removal. The species is also targeted by local hunters who sell it for food at bushmeat markets. While the precise impact of these threats is unclear, it is likely that the current level of offtake is unsustainable given the species’ small range (less than 5,000km2).
Conservation Underway
It is known that the species occurs in the Phou Hin Poun National Biodiversity Conservation Area.
Conservation Proposed
Further research is needed to assess the current population status of this species, and the relative importance of the suspected threats.
Aplin, K. & Lunde, D. 2008. Laonastes aenigmamus. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. <www.iucnredlist.org>. Downloaded on 15 November 2010.

Dawson, M. R., et al. 2006. Laonastes and the “Lazarus Effect” in Recent Mammals. Science  311: 1456-1458.

Huchon, D. et al. 2007. Multiple Molecular Evidences for a Living Mammalian Fossil. Proceedings of the National Academy of Science USA 104(18): 7495-7499.

Jenkins, J. D., Kilpatrick, C. W., Robinson, M. F. and Timmins, R. J. 2005. Morphological and molecular investigations of a new family, genus and species of rodent (Mammalia: Rodentia: Hystricognatha) from Lao PDR. Systematics and Biodiversity 2(4): 419-454.

Lundmark, C. 2005. Hidden in Plain Sight. BioScience 55(8): 720.

Musser, G. G., Smith, A. L., Robinson, M. F. and Lunde, D. P. 2005. Description of a new genus and species of rodent (Murinae, Muridae, Rodentia) from the Khammouan Limestone National Biodiversity Conservation Area in Lao PDR. American Museum Novitates. 3497: 1-31.

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