Abstract
Here, a detailed description of the forelimbs and hindlimbs of all living species of the genus Tympanoctomys are presented. These rodents, highly adapted to desert environments, are semi-fossorial with capacity to move on the surface as well as to build burrows. The shape, structure, and size of the limbs are described. Contrary to what was expected for scratch digging semi-fossorial species, Tympanoctomys have slender humerus, radius and ulna; with narrow epicondyles of the humerus and short olecranon of the ulna with poorly developed processes. Following our descriptions, no intrageneric morphological variation regarding to the configuration of the limbs was detected, probably due to phylogenetic proximity, and not related to specific variations in response to different use of substrates or habits. The obtained results constitute a source of previously unpublished information as well as an important base for future analysis in different studies, such as morphometric, morpho-functional, or phylogenetic researches.
Highlights
Tympanoctomys is member of a clade of the family Octodontidae, restricted to Argentina (Reig 1989; Ojeda et al 2013; Díaz et al 2015)
Tympanoctomys is a polytypic genus containing four living species: T. aureus, T. barrerae, T. kirchnerorum, and T. loschalchalerosorum, of which two species were originally described as separate genera (Pipanacoctomys aureus and Salinoctomys loschalchalerosorum) and T. kirchnerorum was recently described from the central Patagonia of Argentina
Most studies have been limited to one species of Tympanoctomys (T. barrerae) there is almost no information about morphological change within species
Summary
Tympanoctomys is member of a clade of the family Octodontidae, restricted to Argentina (Reig 1989; Ojeda et al 2013; Díaz et al 2015). It was estimated that Tympanoctomys diverged about six million years ago (Gallardo and Kirsch 2001) in coincidence with the origin of deserts at Late Miocene (Gallardo et al 2006); but other authors mentioned different times of divergence from 2.5 to 6.5 million years (see Upham and Patterson 2012; Gallardo et al 2013; Upham and Patterson 2015; Verzi et al 2016; Suárez-Villota et al 2016; Álvarez et al 2017) This genus is one of the few mammals (all rodents) most highly adapted to desert environments (Mares 1975, 1993; Bozinovic and Contreras 1990; Ojeda et al 1996; Mares et al 2000; Honeycutt et al 2003). These results are in accordance with previous morphological and molecular researches where Pipanacoctomys is placed external to Tympanoctomys-Salinoctomys (Barquez et al 2002; Upham and Patterson 2015, 2016)
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