Nothocricetulus, Lebedev & Bannikova & Neumann & Ushakova & Ivanova & Surov, 2018

Lebedev, V. S., Bannikova, A. A., Neumann, K., Ushakova, M. V., Ivanova, N. V. & Surov, A. V., 2018, Molecular phylogenetics and taxonomy of dwarf hamsters Cricetulus Milne-Edwards, 1867 (Cricetidae, Rodentia): description of a new genus and reinstatement of another, Zootaxa 4387 (2), pp. 331-349 : 343-344

Nothocricetulus gen.nov.

Type species: Mus migratorius Pallas, 1773

Diagnosis. Small hamsters with moderately sized tail (~30% of body length), naked palms and soles. Auditory bullae moderately inflated, tube-like anterior processi absent, stapedial foramen present. Hamular process of squamosal is broad, distally spatulated. Molars relatively broad, with widely separated cusps and large anterocones(-conids). In the upper M1 and M2, the median mures formed by the posterior ridges of the para- and protocones and anterior ridges of the meta- and hypocones are characteristically X-shaped, in particular the anterior ridge of the metacone (metalophule) tends to join the posterior ridge of the protocone but not the anterior ridge of the hypocone ( Fig. 7 ). Mesolophids absent. Molar proportion as in Cricetulus . [A detailed description of dentition is provided by Pradel (1981).] Zygomatic plate is straight (as in Cricetus ) in most; however, the morphology of the anterior zygoma is polymorphic in Chinese and Mongolian populations (Lebedev & Potapova 2008) where, in many specimens, the infraorbital foramen is rounded on the outer side and lacks external plate (as in Allocricetulus ).

Differential diagnosis. Nothocricetulus can be distinguished from all other hamsters by molar morphology (position of metalophule on M1 and M2). Among small-sized hamsters, it differs from Allocricetulus by a more slender rostrum and narrower braincase, from Urocricetus and Phodopus by bullae morphology; from the latter genus it also differs by the presence of a well-developed stapedial foramen. Nothocricetulus is separated from Cricetulus proper by the above-mentioned dental traits and also by larger width of the distal part of the hamular process, which is relatively narrow and assymetric in the latter genus, as well as by the shape of the fronto-parietal suture: in Cricetulus the anterior angles of the parietals extend anteriorly from the rostral-most point of the squamoso-frontal suture but are level with the latter in Nothocricetulus .

Etymology Nothos —false, cricetulus —small hamster

Content. a single polymorphic species with several semispecies or subspecies groups (see Lebedev 2000). Interspecific taxonomy requires revision.

The relationships of Nothocricetulus with fossil genera also need clarification. As follows from the cladistic analysis by Bescós (2003) several taxa, which are now attributed to Allocricetus in its wider treatment, can in fact be closer to Nothocricetulus . Nevertheless, it is unlikely that the genus Allocricetus Schaub 1930 as based on A. bursae Schaub 1930 should include Nothocricetulus . The former demonstrates closer affinities to Cricetus and Allocricetulus , which share with it a potential synapomorphy—the presence of enamel on the rear surface of lower incisors (Topachevsky & Skorik 1992), which is absent in Nothocricetulus .

Figures

FIGURE 7. Occlusal view of M1 and M2; (a) Cricetulus barabensis (ZMMU S-187357), (b) Cricetulus longicaudatus (ZMMU S-187364), (c) Nothocricetulus migratorius (ZMMU S-15931), (d) Urocricetus aff.alticola (ZMMU S-155362), (e) Allocricetulus eversmanni (ZMMU S-171981).Arrow рoints to the median mure.