化石闭壳龟的新发现

闭壳龟(Cuora)是龟科(Emydidae)中的一个现生属,有6个现生种,分布于东亚和东南亚,我国产4种。为该地区龟类动物中的一个小类群,以前未有化石发现。本文记述的是闭壳龟属的一个化石新种(Cuora pitheca,sp.nov.),时代为上新世早期。这是该属龟类的首次化石记录。它的发现,不仅把闭壳龟属的历史从现代推至上新世早期,并为探讨该龟类的进化和分布提供重要资料。

NEW FOSSIL CUORA (EMYDIDAE) FROM EARLY PLIOCENE OF YUNNAN

The fossil turtles here described were collected from the Early Pliocene of Lufeng, Yunnan, by a field party of the Laboratory of Paleoanthropology of IVPP in 1977. It is said that the turtles were unearthed together with fossils of Ramapithecus and other mammals. The specimens of turtle consist of at least seven individuals, but only one plastron and carapace are complete or partly complete, others are anterior or posterior lobes of plastron and single bony plates. All the specimens, though somewhat different in size, belong doubt less to the same species. Judging from the hexagonal neurals short-sided behind, the absence of bridge, and the structure of both lobes which were movable when the animal was living, it seems reasonable to consider the present fossils as a member of Cuora.Cuora is a living genus of Emydidae. It has only six species now existing in East and South-east Asia among which four are known in China. It is an Asiatic box tortoise and differs from Cyclemmys by the absence of bridge, and from Terrapene, by its hexagonal neurals short-sided behind. According to the available literatures, no fossil form of Cuora so far has been known in record, the fossils here described therefore become the first occurrence of it, thus tracing the generic history from recent back to Early Pliocene. It is doubtless helpful in studying the origin and the evolution of this group of turtle.By such characters as oval outline of shell, fairly wide vertebral scutes, anterior border of the fourth vertebral scute convex, and less arched carapace, we can distinguish our specimens from all living species of Cuora. It is hence a new species of the genus——Cuora pitheca, the specific name showing that the new form was obtained together with fossil ape. The diagnosis of the species may be grouped as follows:Shell oval in form, carapace not markedly convex, vertebral scutes broad, wider than long, anterior border of fourth vertebral scute convex, plastron notched posteriorly.As for the details of strnctures and the measurements of scutes and plates, references can be made to the figure, plate and tables in the chinese text.In view of the fact that several fossil turtles from Anhui Province may also be members of Cuora, it seems probable that Cuora had a wider distribution in geological time in China, and we will get more fossils of it in future in our country.