Redescription and phylogenetic relationships of Spermophilus citelloides (Rodentia: Sciuridae: Xerinae), a ground squirrel from the Middle Pleistocene - Holocene of Central Europe

Spermophilus citelloides is a poorly known Old World ground squirrel from the Middle Pleistocene - early Holocene of Central Europe that has only been briefly described previously. Here, we expand our understanding of its craniodental morphology by providing the first detailed description of numerous S. citelloides materials from five Late Pleistocene and early Holocene localities of Hungary and Slovakia. Spermophilus citelloides is recognised as a valid species that is characterised by a shallow, gently domed skull with massive and short rostrum, broad interorbital region, strong zygomatic process of the frontal, posteromedially expanding lacrimal, posteriorly narrowed hard palate, wedge-shaped horizontal process of the palatine, small to absent suboptic foramen, thin condyloid neck of the mandible, M3 possessing a metaloph, and anteroposteriorly elongated m3 with strong hypoconulid and entoconulid. A cladistic analysis of 103 craniodental characters scored across 32 ingroup taxa recovers S. citelloides as the sister taxon of living spotted ground squirrel, S. suslicus, thus confirming the hypothesis of close phylogenetic relationships between the taxa. These relationships are further confirmed by the geometric morphometric analysis of the occlusal outlines of the premolars and molars. The alternative hypothesis allying S. citelloides with S. citellus is not supported by our analyses.