贵州的短尾鼩(Anourosorex)化石

贵州发现的属于食虫类 Anourosorex 属的182件标本按齿式可分为两种类型,齿式为的是 A kui; 齿式为的是两新种, A. edwardsi sp. nov. 和 A. qianensis sp. nov.. 含有 A. kui 的岩灰洞、天门洞及穿洞动物群的地质时代可与四川盐井沟及歌乐山中更新世中晚期动物群相对比. A. kui 与较原始的 A. edwardsi 共生的岩灰洞和穿洞动物群的时代可能较之天门洞稍早.较进步的绝灭种 A. qianensis 单独存在于挖竹湾洞、天桥裂隙、白脚岩洞并和云南呈贡三家村晚更新世地点的材料可以对比. 根据齿式及形态特征 A. kui 应是现生种 A. squamipes 的直接祖先.

REMAINS OF THE GENUS ANOUROSOREX (INSECTIVORA, MAMMALIA) FROM PLEISTOCENE OF GUIZHOU DISTRICT

Among the Pleistocene mammMs collected from the deposits of six limestone caves (namely Yanhui, Wazhuwan and Tianmen of Tongzi County, Chuan and Baijiaoyan of Puding County and Tianqiao of Weining County of Guizhou Province) during 1982-83, the materials of the genus Anourosorex (Insectivora, Mammalia) are numerous and rather interesting in dating the fossil bearing beds. On the basis of the presence or absence of the third upper antemolar, the materials can be grouped into two types: A. kui and A. edwardsi n. sp. — A. qianensis n. sp.. The dental formula of the two, therefore, might be expressed as ?and? respectively. The species A. kui is somewhat bigger in size and its zygomatic process is stronger than that of living species A. squamipes. P~4 and M~1 are slightly wider than long. M~2 has straight inner border and developed hypocone and overlaps M~3. The ascending ramus of lower jaw hardly covers M_3 in external view. The lower articular condyle of lower jaw is some distance to the mandibular foramen. Entoeonids of M_(1-2) slightly cone-shaped. On an imcomplete skull (holotype) from Loc. 53 of Koloshan near Chongqin Young C. C. and Liu P. T. (1951, p. 48) stated that this species differs from the living A. squamipes in: (1) somewhat larger size, (2) with about 1 mm diastema between I and the first antemolar, (3) less reduced M~3, and specially (4) with quadrangular M~2. Observation on the original specimen shows that the above mentioned (2) is result of being compressed and deformed. The appearance of the quadrangle or triangle of M~2 depends to a large extent on the development of its hypocone: in almost all specimens of A. kui, the cusp is so strong that the interior and posterior borders of the tooth look straight or slightly concave, but in A. squamipes rather weak and the lingual border of the tooth always directs the posteroexternal. This cusp seems to be absent in A. japonicus Because inclination of the lingual border of M~2 makes its posterior border shortened and straightened, the position of M~3 is different in various species: in A. kui it projects partly behind M~2, but entirely in both A. squamipes and A. japonicus. In addition. P~4 and M~1 are alwys longer than wide in A. kui and shorter in A. squamipes. The new species, A. edwardsi, is much larger in size and the zygomatic process stouter than that of A. kui, P~4 and M~1 are obviously wider than long. M~2 is quadrangular and the hypocone stronger. The ascending ramus of lower jaw is not covering M_3 in external view. The lower articular condyle extends to the posterior border of mandibular foramen. Entoconids of M_(1-2) crested. The skull of the new species, A. edwardsi, is the largest among the known species of Anourosorex. The dental formula differs from those of all the other fossil and living species of this genus of Asia, but has something to do with the European Early Turolian A. kormosi. Distinctive features of A. edwardsi are: (1) larger size, (2) anterior margin of P~4 flattened rather than pointed, and relatively narrower transversely, (3) weaker mesostyle of M~1, (4) superior articular condyle triangular rather than oval, (5) more forward position of inferior articular condyle. The pliocene species A. inexpectatus (Schlosser, 1924) from Ertemte of Inner Mongolia is known only by a posterior, toothless lower jaw fragment. The position of the anterior margin of lower articular condyle of lower jaw, which extends to the positi?n between the mandibular foramen and the inferior temporal fossa when viewed laterally, and the stouter angular process are quite different from the new species A. edwardsi. The dental formula of A. qianensis sp. nov. is same as that of A. edwardsi. but with following differences: (1) smaller size, (2)P~4 smaller than M~1, (3) M~1 narrower transversely, (4) anterior edge of lower articular condyle of lower jaw obviously more backward. These characters indicate that this species is somewhat more advanced than A. edwardsi. The fact that both A. kui and A. edwardsi exist in caves Yanhui, Tianmen and Chuan of Guizhou shows on one hand that the fossil bearing beds of these loealities can chronologically be comparable with those of Koloshan and Yanjinggou of Sichuan, and indicates on the other hand that two forms of dental formula of the genus Anourosorex existed already in middle Middle Pleistocene; A. kui is probably the direct ancestry of living A. squareipes, while A. qianensis from caves Wazhuwan, Baijaoyan and Tianqiao is more advanced than A. edwardsi and became extinct in Late Pleistocene.