摘要
关于二 叠纪箭 石化石的 报道 极少 ，这 是湖 南 首次 发 现的 箭石 化 石，化 石 保存 在上 二 叠统大隆组 的硅质 岩中根 据这些化 石的外部 形态，它 们可归 属于 Ｐａｌａｅｏｂｅｌｅ ｍ ｎｏｐｓｉｓ 属，是箭 鞘亚纲中的原始 类型这 些化石 的发现对 研究中生 代箭鞘 类的起源 具有重 要意义 图３ ，
The fossil belemnoids described here were discovered from the Upper Permian Dalong Formation in Hunan province.There are nearly one hundred specimens,including 1 genus and 1 species. The diagnosis of the species is as follows: Genus:Palaeobelemnopsis Chen,1982 Species:Palaeobelemnopsis sp. Guard small and slender,about 6 times the maximum transverse diameter in length,outline slightly hastate or fusiform.Maximum transverse diameter located the border between apical region and stem region,and nearly cycloid or slightly compressed in anterior of alveolus.Apical angle about 70°.Median ventral groove wide and shallow,sometimes absent.Two dorso-lateral grooves apparent and extending from alveolus to the apex.Phragmocone slender. The outer shape of the guard is very similar to that of P.sinensis and P.minor.Nevertheless,this species differs from the two latters in having many tiny transverse lines covering on the whole surface of the guard.Because all of these specimens are fossils of external mold and no inner structures have been preserved except a piece of siphuncle remains,the species is not given a new species name. Permian belemnoids are rarely found and the Palaeobelemnopsis is a primitive genus of belemnoids,therefore these specimens have important significance for research on the origion of COLEOIDEA.3figs.,4refs.
出处
《湘潭矿业学院学报》
1999年第2期25-29,共5页
Journal of Xiangtan Mining Institute
