关键词: 上猿;中中新世;宁夏

Abstract: The subject of the present paper, a left M2 of Pliopithecus, BPV 261 (housed in Beijing Natural History Museum) , was purchased, purely by chance, in the early spring of 1985 from a "dragon-bone" digger in situ, where he had successfully found teeth and bones of Platybclodon, Listriodon and Stephanocemas. The locality, called Maerzuizigou, lies near the village Dingjiaergou, which is 18 km northeast to Tongxin, the county center. Its geographie position is indicated in text-figure 1.
From the same locality, and chiefly frorn the surrounding area, more materials were collected by the field parties of both the Institute of Vertebrate Paleontology and Paleoanthropology and Beijing Natural History Museum during the last several years. Although the study of the materials is still under way and the geological setting of the area concerned is still being prepared, the geological age of the area in general is clear: It is a little older than the typical Tung-gur faunal age, probably comparable to MN 6 or 7 in the European mammalian biochronology.
During the first half of the present century there were some reports on the possible oceurrence of pliopithecine material in North China. Schlosser (1924) first reported an M3 under the name of Pliopithecus posthumus. However, the tooth is too heavily worn to warrant its taxonomic position as proposed by M. Sehlosser. Recently Ginsburg and Mein (1980) proposed to refer it to a gibbon genus: Krishnapithecus. Later Bohlin (1946) deseribed some very badly preserved specimens and erected for them a new genus, Kansupithecus (without designation of species) , allegedly belonging to the pliopithecine group. Because of their poor state of preservation (a practically edentulous lower jaw fragment and some tooth splits) , again, their true nature is uncertain. Szalay and Delson (1979) provisionally referred them to tPliopithecidae incerta sedis. The Tongxin material, though consisting of only one tooth, represents therefore the first authentie record of the genus in China. In addition, the preservation of the tooth is excellent, the erown features are all clearly demonstrated.
A cursory comparison is enough to reveal that our Tongxin specimen conforms very well with Hürzeler’s diagrammatie presentation of the pliopithecine lower molars based on G?riach material (Hürzeler, 1954, fig. 14) . The features our M2 has in common with Hürzeler’s diagram are the following: 1. The labial wall of the tooth is marked'y slan- ting, so that the labial eusps approximate the lingual ones strongly at the top of the erown. 2. The trigonid is large. basin-shaped. and blocked posteriorly by a well develop- ed metalophid. 3. The talonid eonsists of three cusps: hypoconid, entoconid and hypoco- nulid, without indication of the sixth cusp. 4. The distance between the hypo- and entoconid is longer than that between the proto- and metaconid. 5. The metastylid is tiny, but still discernible. 6. There is a "hinter Hauptleiste" (Remane's term) connecting the hypoeonulid and entoconid. 7. There is a "pliopithecine triangle", which is typical for all the members of the group. 8. There is a weak connection between the hypoconid and metaconid on the bottom of the talonid. 9. The labial eingulum is well developed, interrupted only at the midpoint. The enumeration of these characters in common leaves no room for doubt that the Tongxin specimen should refer to the genus Pliopithecus.
The systematies of the pliopithecine group in now rather complicated. Ginshurg and Mein (1980) proposed to split Pliopithecidae into two subfamilies: Crouzelinae and Pliopithecinae. However, Szalay and Delson (1979) already seriously doubted the validily of the genus Crouzelia, which served the base for Ginsburg and Mein's separation of the subfamily Crouzelinae, based chiefly on the assumption that Crouzelia was based on wrong identification of the deciduous teeth as permanent ones. The careful observation of the cast of the type speeimen shows that the original teeth identification was correct, therefore Ginsburg and Mein's subdivision of the family Pliopithecidae is to be considered tenable. Our speeimen from Tongxin should obviously be exeluded from the subfamily Crouzelinae, which is characterized by the lophodont tendeney of the main cusps, reduction of the entoconid and hypoconulid and less developed cingulum. According to Ginsburg and Mein, Pliopithecinae consists of only one genus and three species: Pliopithecus piveteaui, P. antiquus and P. vindobonensis. The Tongxin specimen is evidently closest to the later speeies in both morphology and size. Nevertheless, they differ still considerably: 1. The Tongxin specimen is even larger in size than that in the iater species. In fact our specimen represents the largest individual ever found for the genus Pliopithecus (see table 1) . 2. The secondary structures on the erown surface of the Tongxin specimen are rieher developed. 3. The "pliopithecine triangle"is still not completely closed in our specimen.
Our new specimen may well represent a new species of the genus, but the paueity of the material made us hesitating in doing so.

Key words: Pliopithecus; Middle Miocene; Ningxia