腊玛古猿和西瓦古猿的形态特征及其系统关系——下颌骨的形态与比较

本文通过禄丰腊玛古猿和西瓦古猿的下颌骨与现代大猿类和其它同时代的古猿及南方古猿类的下颌骨的比较得出:禄丰的两类古猿有不少特征与猩猩相似,因此它们可能与猩猩有较密切的关系,两类古猿可能是同一类型的雌雄个体。但另一方面,禄丰腊玛古猿又显示出一些与南方古猿相似的性状,因而另一种可能是腊玛古猿是与西瓦古猿不同的类型,它比西瓦古猿更接近于人猿的共同主干。

MORPHOLOGICAL FEATURES OF RAMAPITHECUS AND SIVAPITHECUS AND THEIR PHYLOGENETIC RELATIONSHIPS -MORPHOLOGY AND COMPARISON OF THE MANDIBLES

The fossils of hominoids bearing locality at Shihuiba, Lufeng County, Yunnan province had been digged for eight seasons during 1975-1981. Mandibles of Ramapithecus and Sivapithecus of the following were unearthed. The three comparatively complete specimens of mandibles of Ramapithecus and four of Sivapithecus and more than 20 pieces of their fragments were studied and compared with those of extant large apes and those of related fossil specimens. The main characters of mandibles of Ramapithecus and Sivapithecus from Lufeng are as follows: 1. The frontal part of the symphyseal region and the frontal teeth are almost vertically oriented. 2. The depths of the symphyseal region are large compared with those of the posterior of corpora. 3. The alveolar planes are moderately oblique. 4. The superior transverse tori are not pronounced. 5. The genioglossal fossae are of medium breadth. 6. The inferior transverse tori are strongly developed and the bottom of them slants postero-superiorly. 7. The depths of corpora at P4 and M3 are comparatively great. 8. The ascending rami are deep and broad and perpendicular to the corpora with their frontal margin relatively more in front. Comparison of mandibles from Lufeng with those of the extant great apes suggests that they differ greatly from those of gorilla and chimpanzee, but close to that of orang-utan in five points as follows: 1. The frontal part of the symphyseal region and the frontal teeth are almost vertically oriented. 2. The alveolar planes are moderately oblique. 3. The superior transverse tori are not pronounced and the breadths of genioglossal fossae are medium. 4. They are well-matched in the depth and broadness of posterior parts of corpora and the relation of proportion in depth at the symphyseal region and the lateral part of corpora are comparatively similar between the Sivapitkecus from Lufeng (PA 820) and the male orang-utan (No. 925). 5. The depth of ascending ramus of Sivapithecus from Lufeng corresponds to that of male orang-utan and the relation of proportion is comparatively similar between the depth of ascending ramus and that of corpora. These resemblance between both further indicates that the two types of hominoids from Lufeng are most similar to orang-utan among the living great apes. The mandibles of hominoids from Lufeng especially Ramapithecus when compared with those of Australopithecus present the following main similar characteristics. 1. The frontal part of corpora and the frontal teeth are almost vertically oriented. 2. The sizes of frontal teeth particularly canines, are small and vertically oriented. 3. The cheek teeth are megadontic (relative to body size) with very thick enamel. 4. The bottoms of inferior transverse tori are oblique postero-superiorly and strongly projected backward. 5. The ascending rami are deep and broad. In short, their common features are: their dentition possesses strong function of cutting and grinding; there are massive mandibular buttresses-the inferior transverse tori in inner side of the symphysis, and the ascending rami are deep and broad. These features may be the result of eating rough diet. As many characteristics of two kinds of hominoids from Lufeng are similar to those of orang-utan, it seems to indicate that they have dose relationships. These two kinds probably belong the same species with great sexual dimorphism. On the other hand, Ramapithecus from Lufeng also shows some features similar to Australopithecus. Thus, there is also possibility that Ramapithecus is a different taxon from Sivapithecus, and it is nearer to the common stock of man and African large apes.