Morphological and molecular investigations of a new family,genus and species of rodent (Mammalia: Rodentia: Hystricognatha) from Lao PDR

During biodiversity surveys in Khammouan Province, Lao Peoples Democratic Republic, specimens of an unknown species of hystricognathous rodent were discovered in local markets being sold for food; local hunters explaining that these rock rats were trapped in the nearby limestone karst. These specimens are described here on the basis of their unique combination of external and craniodental features as members of a new family, genus and species, using comparative morphological and molecular data. Phylogenetic analyses of morphological data and of 12S rRNA and cytochrome b are presented on selected taxa from all suborders of Rodentia. The results of the molecular and morphological analyses are compared and provide the basis for a discussion of relationships of the new taxon within the Rodentia and Hystricognatha. The disjunct distribution of hystricognaths is recognised as problematic, with most families occurring in the main distributional area of South America, several others in Africa and only one family distributed in Africa and Asia. The presence of an additional hystricognath family in Southeast Asia poses interesting questions and consideration is given to the way in which this new taxon fits into the theories of the biogeographical and evolutionary history of other hystricognaths. Features of possible ecomorphological significance are briefly discussed, such as the apparent adaptations to a rock dwelling existence evident in various features of the external morphology and comparisons are made to the morphology of other known saxicolous rodents.