湘西溶溪组的棘鱼化石及其层位

SOME FIN SPINES OF ACANTHODII FROM EARLY SILURIAN OF HUNAN, CHINA

本文介绍了目前我国最低含鱼化石地层,即湘西早志留世(Llandovery 期)溶溪组的地区性地质剖面和产自该组七个类型的棘鱼鳍刺化石,并根据其同层中所产的无脊椎动物化石论证鱼化石层的层位.鱼化石本身所表现出的原始特性与这一结论是谐调的.

The fin spines of Acanthodii described in this paper were collected by the author during the 1982-1984 field seasons from the uppermost part of Rongxi Formation in Wentang and Zhangjiajie, located in Dayong district of western Hunan. It is the earliest Osteichthyes discovered in China as well as in Asia. Because the specimens have neither basal-root of fin spine preserved nor the spine linking with fish-bodies, only a number of disassociated spines are found, therefore this paper is unable to refer their systematic classification and establish new genus or species. On the basis of only exterior pattern, the spines are grouped into 7 types of Acanthodii temporarily. Rongxi Formation with its associated invertebrates in the overlying and underlying beds, has been considered as middle-late stage of early Silurian by most of Chinese geologist for many years. In view of the primitive nature of Agnatha and Acanthodii, bearing fish beds are here proposed to be late early Silurian, which roughly agrees with that of invertebrates.