Pawsitively prehistoric

First described from Laos in 2005, the Laotian rock rat Laonastes aenigmamus quickly gained fame as one of the most remarkable “living fossil” discoveries in modern mammalogy.

A. Abramov (Zoological Institute RAS) with Laonastes aenigmamus in Laos in 2008

The Laotian rock rat is a small, nocturnal rodent inhabiting rugged karst landscapes (Jenkins et al. 2005; Nguyen et al. 2014). Its robust body, dense fur and long, squirrel-like tail reflect adaptation to a rocky, largely scansorial lifestyle. Despite its modest

appearance, Laonastes represents one of the most surprising zoological findings of recent

decades and has attracted broad interest from systematists and paleontologists.

Morphological and molecular data show that Laonastes is the only extant representative of the rodent family Diatomyidae, previously known exclusively from Oligocene – Miocene fossils and thought to have been extinct 11 million years (Jenkins et al. 2005; Dawson et al. 2006; Huchon et al. 2007). Laonastes is separated from the closest living rodent family by 44 million years. This unexpected survival of an ancient lineage — sometimes called the “Lazarus effect” — has made Laonastes a key taxon for understanding deep splits among rodent clades and the biogeographic history of Southeast Asia.

Today, we present a chromosome-length genome assembly of Laonastes aenigmamus (2n=36) from Vietnam, generated using a combination of long-read sequencing and Hi-C scaffolding. The assembly provides a crucial genomic resource for exploring the evolutionary history of Diatomyidae, testing hypotheses about cryptic species diversity within Laonastes, and examining patterns of genome conservation and rearrangement over tens of millions of years.

The data was generated from the fibroblast cell line LAON2m prepared from a tail sample of male Laonastes sp. collected in Thuong Hoa, Quang Binh, Vietnam, and provided by Alexey V. Abramov (Zoological Institute RAS).

References

• Dawson MR, Marivaux L, Li CK, Beard KC, Métais G. Laonastes and the "Lazarus effect" in recent mammals. Science. 2006 Mar 10;311(5766):1456-8. doi: 10.1126/science.1124187. PMID: 16527978.

• Huchon D, Chevret P, Jordan U, Kilpatrick CW, Ranwez V, Jenkins PD, Brosius J, Schmitz J. Multiple molecular evidences for a living mammalian fossil. Proc Natl Acad Sci U S A. 2007 May 1;104(18):7495-9. doi: 10.1073/pnas.0701289104. Epub 2007 Apr 23. PMID: 17452635; PMCID: PMC1863447.

• Jenkins PD, Kilpatrick CW, Robinson MF, Timmins RJ. (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. doi:10.1017/S1477200004001549 (HTML abstract). Erratum: Systematics and Biodiversity 3(3):343. doi:10.1017/S1477200005001775

• Nguyen DX, Nguyen NX, Nguyen DD, Dinh TH, Le DT, Dinh DH. Distribution and habitat of the Laotian Rock Rat Laonastes aenigmamus Jenkins, Kilpatrick, Robinson & Timmins, 2005 (Rodentia: Diatomyidae) in Vietnam. Biodivers Data J. 2014 Dec 25;(2):e4188. doi:10.3897/BDJ.2.e4188. PMID: 25589873; PMCID: PMC4290499.