Cranial Anatomy of the Desert Dormouse, Selevinia betpakdalaensis (Rodentia, Gliridae), revealed by Micro-Computed Tomography

Abstract

The dormice (Gliridae) represent a relatively small family of rodents, but exhibit considerable 21 variation in their cranial anatomy. The skull morphology of almost all genera of dormice was 22 described from osteological specimens by Wahlert et al. (1993). However, the rare desert 23 dormouse, Selevinia betpakdalaensis, was only assessed using previous descriptions and 24 photographic images, resulting in difficulties with assigning all cranial features within this 25 particular genus. In this study, the crania and mandibles of two adult individuals of this genus 26 were scanned using micro-computed tomography and virtually reconstructed. From these 27 reconstructions, we describe in detail the highly unusual cranial and mandibular morphology 28 of the desert dormouse and determine the states of the cranial and mandibular characters 29 described by Wahlert et al. (1993). These morphological characters were used to compare this 30 species with previously described dormouse genera, showing a clear resemblance between 31 Selevinia and the small mouse-tailed dormouse genus Myomimus. Derived morphological 32 features unique to Selevinia indicate clear adaptations to a desert-like environment, as well as 33 hinting towards an insectivorous diet and burrowing lifestyle.34 35 Selevin (Bashanov and Belosludov, 1941). Initially placed in Muridae based on its dental 39 formula, further analyses led to the first description of this species published in English 40 (Bashanov and Belosludov, 1941), in which it was placed in a new monospecific family, 41 Seleviniidae. These authors mentioned the close resemblance of the skull morphology of this 42 species with that of members of Gliridae (Myoxidae), but highlighted the atypical dental 43 structures within this species in comparison to dormice. Ognev (1947) identified the animal as 44 a highly derived dormouse and emphasised the resemblance of this species to Myomimus. He 45 therefore created the subfamily Seleviniinae within the family Gliridae. More recent analyses of the enamel structure in this animal and other dormice also incorporated Selevinia within 47 Gliridae, and no longer acknowledged Seleviniidae as a sister group of Gliridae (von Koenigswald, 1992). Storch (1994) assigned Myomimus and Chaetocauda to Seleviniinae 49 alongside Selevinia, regarding it as the most primitive of all extant dormice subfamilies. In 50 contrast, Yachontov and Potapova (1991) considered Selevinia to be more closely related to 51 Muscardinus and Glis, belonging to the subfamily Glirinae. Later, Potapova reasserted the close 52 relationship between Myomimus and Selevinia based on middle ear morphology (Potapova, 53 2001). Wahlert et al. (1993) placed Selevinia and Myomimus in the tribe Seleviniini, which, 54 joined with the tribe Leithiini, formed the subfamily Leithiinae. Due to the scarcity of accessible 55 specimens, Selevinia was not included in the phylogenetic analyses of the Gliridae based on 56 molecular data by Montgelard et al. (2003) or Nunome et al. (2007). The exact placement of ...

Comparative morphology of the dormouse skull

“…This is the result of the extremely reduced molars within this specimen, corresponding with the relatively short molar rows seen in Graphiurus . The Selevinia skull also suggests morphological similarities with Dryomys (PC2) and Myomimus (PC4), in line with previous studies of this specimen (Hennekam et al, 2020a). In both datasets, the hazel dormouse Muscardinus avellanarius is very different compared to other species.…”

“…All species within Gliridae appear to be omnivorous to some degree, although some are clearly more faunivorous or herbivorous than others (Potapova & Rossolimo, 2008; Holden-Musser et al, 2016). The reduced molar rows in Selevinia and Graphiurus ocularis are thought to be related to a highly insectivorous diet (Webb & Skinner, 1995; Holden-Musser et al, 2016; Hennekam et al, 2020a). Glis, Glirulus, Muscardinus and the thick-tailed African dormouse Graphiurus crassicaudatus are considered to be the more herbivorous dormice.…”

“…However, both genera are considered to be relatively insectivorous (Holden-Musser et al, 2016). Molars in both genera are generally concave, lacking the complex architecture of ridges seen in many other dormouse species (Wahlert et al, 1993; Hennekam et al, 2020a).…”

“…Clear morphological variation is present both between (Wahlert et al, 1993; Hennekam et al, 2020a), and within dormouse genera (Storch, 1978 and Figure 1). In order to understand the morphological traits within this family, the extent of this inter- and intrageneric morphological variation will be analysed.…”

“…Dispersed widely throughout Africa and Eurasia, the family occupies various ecological habitats, including tropical forests in Africa and deserts in central Asia. Dormouse species vary significantly in both cranial and mandibular morphology, with some of these morphological variations thought to be related to adaptations to specific habitats and diet (Wahlert et al, 1993; Hennekam et al, 2020a). The fossil record shows the radiation of Gliridae to start during the Early Eocene (Vianey-Liaud, 1994), with the opening of the North Atlantic, and to peak around the late Early Miocene (Daams & de Bruijn, 1995).…”