Belomys pearsonii (Gray, 1842)

Pang, Li-bo, Chen, Shao-kun, Hu, Xin, Wu, Yan & Wei, Guang-biao, 2024, Fossil flying squirrels (Petauristinae, Sciuridae, Rodentia) from the Yumidong Cave in Wushan County, Chongqing, China, Fossil Record 27 (1), pp. 209-219 : 209-219

Belomys pearsonii (Gray, 1842)

Fig. 3 D, E ; Suppl. material 1: table S 4

Materials.

As in Suppl. material 1: table S 1, there are one maxillary bone and 11 mandibular bones from the layer ②-2, one mandibular bone from the layer ③, two mandibular bones from the layer ④, two mandibular bones from the layer ⑤, one mandibular bone from the layer ⑥ and one mandibular bone from the layer ⑩.

Description and comparison.

The mandible and teeth of Belomys pearsonii are very similar to Trogopterus xanthipes , but there are still some differences. The most obvious is their size: T. xanthipes is much larger than B. pearsonii and there is almost no overlap of the measurements of their cheek teeth (Suppl. material 1: tables S 3, S 4). Additionally, there are discernible differences of cheek tooth characteristics between these two species: 1) B. pearsonii is more lower-crowned than T. xanthipes ; 2) P 3 of B. pearsonii is closer to the protocone of P 4 than that of T. xanthipes ; 3) compared with B. pearsonii , P 4 / p 4 of T. xanthipes is much larger than upper / lower molars; 4) the protocone of P 4 - M 2 of B. pearsonii is more developed than that of T. xanthipes , but the hypocone is somewhat weaker; 5) the hypocone of M 3 of T. xanthipes is permanent and connects with the metaconule by a straight metaloph, but the hypocone and the metaloph of M 3 of B. pearsonii are absent.

There are three species in the genus Belomys , B. pearsonii , B. parapearsoni and B. thamkaewi . B. parapearsoni is only known from the Early Pleistocene. It is smaller than B. pearsonii , with lower tooth crown, less developed mesostyle, less developed mesostylid and more developed hypoconid. B. thamkaewi was unearthed from cave deposits of the Late Pleistocene in Thailand and its validity is yet to be discussed. Chaimanee and Jaeger (2000) thought it was very similar to B. pearsonii , except the somewhat larger size. However, their measurements seem doubtful, but even so, the data do not exceed the data range of fossil B. pearsonii from China.

Figures

Figure 3. Trogopterus xanthipes (A – D) and Belomys pearsonii (E, F) from the Yumidong Cave. A. 12 YMDT 4 ② 30.2, left mandible with lower incisor and p 4 - m 3, occlusal (1), labial (2) and lingual (3) view; B. 12 YMDT 4 ② 35.1, right dp 4 - m 3, occlusal view; C. 12 YMDT 4 ② 35.7, left P 4 - M 2, occlusal view; D. 12 YMDT 4 ② 60.3, right M 1 – M 3, occlusal view; E. 12 YMDT 4 ② 35.9, left P 3 - M 3, occlusal view; F. 12 YMDT 4 ② 35.8, right mandible with lower incisor and p 4 - m 3, occlusal (1), labial (2) and lingual (3) view. Scale bar: 5 mm (A 1, B – E, F 1); 10 mm (A 2, A 3, F 2, F 3).