摘要
本文记述了近年来经过多次发掘和采用筛洗方法从禄丰古猿化石产地获得的一批竹鼠化石标本,共有一属3种:Brachyrhizomys nagrii;Brachyrhizomys cf.pilgrimi和Brachyrhizomystetracharax以及2枚单个牙齿属于暂不宜订种属的类型。
Lufeng rhizomyid fossils collected by excavation and underwater sieving of fossili- ferous sediments, are studied in this paper.
The specimen referable to Brachyrhizomys nagrii is a left lower dentition with M1-M3 (V. 8126). Length of M1-M3 is 11.75mm. Both size and characters (such as short M3 and an elongated mesolophid on M2) agree well with Siwalik specimens (Fig. 4).
The specimens identifiable to Brachyrhizomys cf. B. pilgrimi are a left dentary with M1-M3 (V8127. 1), a right M3 (V8127. 2) and an I1 (V8127. 3). This is a large species with heavy deep dentary (depth below M1=15.4mm) and massive incisors. It also is the biggest one of three species of Lufeng Brachyrhizomys. An apparent trait is suppression of mure on M2-3. The narrow connection may not be present in early wear. Length of M1-M3 is 15.6 mm and more closer to B. cf. pilgrimi than to B. pilg-rimi of Siwaliks in size (Fig. 5, A, B and C).
The third species is B. tetracharax to which the most of the rhizomyine fossils from Lufeng Ramapithecus locality belong. The materials include an incomplete skull and associated lower jaw (V8128. 1), five maxilla fragments (V8128. 2-6). fourteen lower jaws (V8128. 7-20). Fifty five isolated upper and lower chack teeth (V8128. 21-75), eleven isolated upper and lower incisors (V8128.76-86). Unfortunately, the skull and associated lower jaw are crushed and flattened laterally (Fig. 6, A). The portions of it preserved are the ear region of two sides, partial right palate and left zygoma, partial maxilla, premaxilla, temporal bone and nasal. The infraorbital foramina were damaged and the shape of their ventral slit can not be observed. The dentary is deep. In general, the upper dentition is longer than the lower one. Average length of them is 12.28 mm and 14.30 mm respectively. It is undoubtedly to refer the specimens from Lufeng to B. tetracharax, although there is discrepancy between the dimensions of the cheek teeth of Lufeng and Siwalik. M1 has four roots. M3 elongates transversely. There is a strong mesolophid on M2 and an evident mure on worn M2_3. M3 extends longitudinally. These traits distinguish the specimens from the other species easily. The yariations of upper and lower cheek teeth manifested by differences of wear stage in size and pattern of occlusal surface are shown in Fig. 6.
In addition, two isolated cheek teeth are referred to Rhizomyidae indet. A right M1 with four roots (V8129) possesses an antero-lingual flexus (Fig. 7). Another right M8 with a root (V8130) has been well worn and only retained lingual reentrant and three enamel lakes on occlusal surface (Fig. 8).
The best known record of rhizomyid evolution is documented in Siwaliks of Pa-kistan. It is considered to be a standard for comparison of fossil rhizomyids through-out the world especially Asia. Three species of Brachyrhizomys mentioned above have known temporal ranges in Pakistan and coexisted for a short time at 8 Ma. So Lufeng hominoid fauna can be placed about 8 Ma or perhaps a bit later.
出处
《人类学学报》
1986年第1期54-67,共14页
Acta Anthropologica Sinica
关键词
禄丰古猿化石产地
最晚中新世动物群
啮齿目
低冠竹鼠
Ramapitheeus fossil locality of Lufeng
The latest Miocene fauna
Rodentia
Brachyrhizomys
