Cricetus cf. runtonensis NEWTON , 1909

Sabol, Martin & Zervanová, Júlia, 2014, Cricetus Cf. Runtonensis (Newton, 1909) (Cricetidae, Rodentia) From Za Hájovnou Cave (The Czech Republic), Acta Musei Nationalis Pragae Series B 70 (1 - 2), pp. 55-58 : 56-57

Cricetus cf. runtonensis NEWTON, 1909

Text-fig. 2

1909 Newton, E. T., Hamster remains from the Norfolk Forest Bed. Geological Magazine, 6, London, 110-117.

L o c u s T y p i c u s. West Runton , Norfolk, England

(Cromerian Complex, early Middle Pleistocene).

S t r a t i g r a p h i c a n d g e o g r a p h i c r a n g e. Early to late Middle Pleistocene (Nagyharsányhegyian to Solymárian substages), Europe.

S p e c i e s c h a r a c t e r i s t i c s. A relatively large extinct representative of the genus Cricetus , smaller than C. major , but larger than C. praeglacialis and C. cricetus , with a cusp-shaped entostyle on M1 and M2, and an ectostyle on m2 and m3 with more frequently doubled mesolophid in stratigraphically later forms ( Hír 1997b, c, 1998; modified).

M a t e r i a l. A right fragmented mandible with dentition (incisor, isolated m1, and m2 – m 3 in the rock) and a left calcaneus. The bones are a light colour (brown-white) and teeth crowns are white.

D e s c r i p t i o n. The anterior part of the mandible fragment includes a slightly damaged incisor. The mental foramen is large, situated below the diastema, between the incisor and m1. The rest of the mandible ramus is located below the molars in the rock. The m1 is damaged in the posterior part on both lateral sides. This tooth is isolated but in anatomical order with m2 and m3, belonging to the posterior part of the mandible. The double-cuspid anteroconid of m1 is more or less isolated, slightly worn on the lingual conelet tip and damaged on the buccal conelet. The anterolophulid can be considered more likely to be reduced rather than connected to the buccal conelet of the anteroconid. Other cuspids (metaconid, protoconid, entoconid, hypoconid) are moderately worn. The mesolophid is missing. Since the posterior part of the crown is damaged, the morphology of the posterolophulid cannot be classified. The remaining part, however, suggests that it was probably simple rather than ramified. Based on that, this molar would more likely represent morphotype F1a than E1a as defined by Hír (1997a, c, 1998). The two morphotypes differ in the level of anterolophulid reduction (reduced in the F1a morphotype and non-reduced, connected to the anteroconid buccal conelet in the E1a morphotype).

The lower molars (m2 and m3) are mostly covered by rock, and only the lingual cuspids (larger metaconid and lower entoconid) can be recognized. The antero-buccal part of m2 crown is absent.

The left calcaneus is completely preserved, probably belonging to the same individual as the fragmented mandible with teeth. The calcaneus is 9.0 mm long and 6.1 mm wide from the peroneal process to the medial tip of the sustentaculum. The calcaneal tubercle is long, transversely compressed with a slightly expanded proximal head. The calcaneoastragalar facet is convex and smoothly rounded. The sustentacular facet is flat and faces more or less dorsally. The narrow and relatively poorly defined sulcus calcaneus separates the sustentacular facet from the calcaneoastragalar facet. The sustentaculum talus is prominent, projecting medially. The distinct, shelf-shaped peroneal process is more expanded proximodistally, situated almost at the same level as the sustentaculum talus. The anterior plantar tubercle is faint, positioned more medially.

Figures

Text-fig. 2. Fossil remains of Cricetus cf. runtonensis NEWTON, 1909 from Za Hájovnou Cave (Moravia, Czech Republic), Middle Pleistocene. a–b) lower molar row (a – occlusal view, b – lingual view); c) m1 dext., occlusal view; d–e) left mandible fragment with incisor (d – lingual view, e – buccal view); f) calcaneus sin., anterior view.