周口店地区仓鼠材料的重新观察

经重新鉴定,周口店地区第四纪期间共有4属7种仓鼠,包括大型种类Allocricetus ehiki、A. teilhardi sp. nov. 及Cricetinus varians和小型种类Cricetulus longicaudatus, C. barabensis griseus, C. b. obscurus, C. cf. migratorius, Phodopus sp.其中A. ehiki-A. teilhardi sp. nov.,C. varians-现生种“C.”triton及小型仓鼠可能分别和中国新第三纪晚期的Sinocricetus, Kowalskia等有较密切的亲缘关系。

REVISED DETERMINATION OF THE FOSSIL CRICETINE (RODENTIA MAMMALIA) OF CHOUKOUTIEN DISTRICT

1818 specimens of Cricetinae from Locs. 1, 3, 9, 12, 13, 15 and 18 of Choukoutien have been restudied, though in the original collections could not been located or might have been lost. Seven broken skulls, one upper jaw and 62 mandibles from Locs. 12 and 18, which were originally described as Cricetinus cf. varians or ? Cricetulus (Cricetinus) cf. varians, are here allocated to the Early Pleistocene European species Allocricetus ehiki. Eight upper jaws and 21 mandibles from Loc. 9, three broken skulls and one mandible from Loc. 13 and one mandible from the Layer 6 of Loc. 1 are distinguishable from those of "C. varians" and named as Allocricetus teilhardi sp. nov., The rest of larger hamster from Locs. 1, 3, 9, 13 and 15 can be regarded as the real C. varians. Among those materials once described as Cricetulus of. griseus and C. of. obscurus, one broken skull, two upper jaws and 182 mandibles from Loc. 1, four madibles from Loc. 3, nine mandibles from Loc. 9, four mandibles from Loc. 15 and seven mandibles from the Upper Cave should be refered to Cricetulus longicaudatus. One left upper jaw with M~(1-2) from Loc. 3 and one left upper jaw with M~(1-3) are considered as Phodopus sp. and Cricetulus of. migratorius respectively. In addition, the names of both C. b. griseus and C. b. obscurus are still retained in this paper. The skulls of A. ehiki from Choukoutien are in agreement with that from Hungary nearly. in all respects, such as the straight dorsal profile, width of the interorbital space (4.4—4.9 to 4.4mm), length of the nasals (11.1—13.5 to 12mm), upper cheek tooth rows (5.15—5.7 to 5.6mm), incisive foramina (6.2—8.1 to 7.9mm), diastema (8.3—12.1 to 11 mm) and width of the palate between the two M~1 (3.6—4.6 to 4.4 mm). The absence of mesolophids on M_(1-2) is the most important character differing from either the fossil species C. varians or the living one "C". triton of China. The skull of Cricetinus varians differs from the "C". triton by its larger size, wider and less tapering rostrum, more rapid forward expanded nasals, wider interorbital space, especially the nearly straight dorsal profile as in Allocricetus. The new species, Allocricetus teilhardi, is the largest known from of Choukoutien. It possesses a straight dorsal profile and an evenly rostrum as in both A. ehiki and C. varians, but its narrower and longer anterorbital foramen, rostrum, interorbital space and larger cheek tooth rows are not the same as in both latter species. The shape of the brain ease and the interparietal (pentagon) are almost similar to those in C. varians and "C". triton, but different from A. ehiki (triangle). In distinguishing various smaller hamsters known from Choukoutien, with the exception of the size and crown shape shown in text fig. 4, the size of an angle between the lines linking Protocone-Hypocone and Protocone-Paraeone can better express the opposite degrees of the chief outer and inner cusps on the upper molars. The angles, which in C. longicaudatus, C. b. griseus, C. b. obscurus, C. of. migratorius and Phodopus sp. are 70°, 72—74°, 78—79°, 84° and 70° respectively, are fundamentally in agreement with those of the corresponding living forms. The relative age sequence of the main Localities of Choukoutien is shown as in text fig. 5. Phylogenetically the Early Pleistocens species, A. ehiki, might occupy a transitional position between the Pliocene Sinocricetus and the Middle Pleistocene A. teilhardi sp. nov., which probably became extinct at the Upper Cave stage. Compared with the above two species, C. varians is, after all, closer to the living "C". triton and can not be on the same phylogenetic line with Allocricetus, and perhaps in close relationship with the Pliocene Kowalskia. Among the smaller species, C. longicaudatus has hold sway for retaining some primitive features of the Pliocene Nannocricetus on its cheek teeth.