禄丰西瓦古猿和腊玛古猿的关系及其系统地位

RELATIONSHIP BETWEEN LUFENG SIVAPITHECUS AND RAMAPITHECUS AND THEIR PHYLOGENETIC POSITION

本文对十年来采集的禄丰腊玛古猿和西瓦古猿化石进行阶段性研究,对这两类古猿的关系及其系统地位提出进一步的看法:禄丰腊玛古猿和西瓦古猿在形态上表现出同种二形的性质,因此它们是同一个种的雌雄个体,它们的学名被修订为禄丰西瓦古猿(sivapithecuslufengensis);禄丰标本的有些特征不同于同时代的其他古猿,而相似于南方古猿和非洲猿类,因此它们可能是向南方古猿和非洲猿类方向进化的一个代表类型。

A great number of fossils of Ramapithecus and Sivapithecus were collected at the Shihuiba locality in Lufeng County, Yunnan Province from 1975-1983. The material consists of the following specimens. Ramapithecus: three crania, five mandibles. 23 pieces of fragments of crania and jaw bones, 22 dental rows and 329 isolated teeth, as well as two phalanges; Sivapithecus: two crania, five mandibles, 24 pieces of fragments of crania and jaw bones, seven dental rows and 321 isolated teeth, as well as one scapula and one clavicle. This paper is a detailed study of the material. 1. Crania The similarities and differences between Lufeng Sivapithecus and Ramapithecus are briefly described here. They share the following characteristics in the cranial mor-phology: The supraorbital ridges are slightly developed and uncontinuous with wide and eoncave glabella region. The supraorbital sulcus is not apparent. The interorbital region is very wide. The orbital contours are square in shape with rounded corners. The nasal aperture is narrow and pear-shaped. The faces are short. The zygomatic processes of maxilla are situated more anteriorly than in extant great apes, and it is thus lees pro-gnathous. The nasoalveolar clivus is short and slightly sloped backward, and conti-nued with the palatine process of maxilla of the base of nasal cavity. The different features of the eranial morphology between Lufeng Sivapithecus and Ramapithecus are as follows: 2. Mandibles The common characteristics of the mandibles of Sivapithecus and Ramapithecus from Lufeng are as follows: The anterior teeth are vertically orientated. The frontal surface of the symphyseal region is vertical and the inferior part oblique rearward, especially in Ramapithecus. The alveolar plane is moderately oblique. The superior transverse torus is not prono-unced. The breadth of genioglossal fossa is medium and its base extends backward gently. The inferior transverse torus is present above the plane of the basal border of body of mandible, it is thiek and projects posterosuperiorly. The digastric fossa on the basal margin of the symphysis is developed. A digastrie spine is present on the middle of the frontal margin of the digastric fossa. The middle sagittal ridge is leng-thened backward from this spine, and turns in at the bottom of the genioglossal fossa. The mental foramen is single and opens anterosuperiorly. The cheekteeth are orientat-ed posteriorly in relation to the ascending ramus. The buccinator grooves are broad. The different features between the two kinds of mandibles from Lufeng are as follows : The middle eminence on the frontal surface of the symphyseal region of Ramapi-thecus shows Y-shaped ridge and that of Sivapithecus is perfectly round. The thick-ness of inferior transverse torus of Ramapithecus is great. Its base extends slightly posterosuperiorly, and its posterior margin is nearer to the plane of the basal border of body of mandible. In Sivapithecus, the thickness of inferior transverse torus is very great, its base extends more posterosuperiorly. The posterior margin of inferior torus is far from the plane of the basal border of body of mandible. The frontal den- tal arch of Ramapithecus is slightly round, and that of Sivapithecus a little jut forward. The dental arch of Ramapithecus is sub V-shaped, and its cheekteeth rows gradually diverge as it extending posteriorly. In Sivapithecus, the dental arch is U-shape, and cheekteeth rows extend parallely backward, and diverge only slightly at posterior part. The position of mental foramen of Ramapithecus is higher, at half of the depth at P4, and that of Sivapithecus is lower, at the inferior third of the depth between P3-P4. 3. Teeth In general, the teeth of Lufeng Sivapithecus and Ramapithecus are very similar to each other in morphology except canines and lower third premolars. However the teeth of Sivapithecus are larger than those of Ramapithecus. The similarities of the teeth between Lufeng Sivapithecus and Ramapithecus are as follows. The labiolingual dimensions of the