滇东北早寒武世梅树村阶单板类及其新属种研究

EARLIEST CAMBRIAN MONOPLACOPHORA IN NORTHEASTERN YUNNAN WITH SOME NEW GENERA AND SPECIES

本文描述了云南东部早寒武世早期梅树村阶软体动物单板类化石 ,计有 5新属 7新种和 1个未定种 ,它们是 Striatoconusyuluensisgen.etsp.nov.,Striatoconussp.,Aegitellusconcentri-cus gen.et sp.nov.,Tubatoconus yuluensis gen.et sp.nov.,Papilloconus explanatus gen.etsp.nov.,Masculuconuscurvativusgen.etsp.nov.,H elcionella bellussp.nov.,Igorella minutasp.nov.。证明了早期软体动物单板纲已有较高的属种分异度 ,认为软体动物的最早祖先应该出现在前寒武纪。本文还提出了壳体形状、肌痕和显微结构可以作为鉴定单板纲的依据。

Described in the present paper are monoplacophorans from the Earliest Cambrian Meishucunian Stage in northeastern Yunnan, including 5 new genera, 7 new species and 1 undetermined species, namely Striatoconus yuluensis gen. et sp. nov., Aegitellus concentricus gen. et sp. nov., Papilloconus explanatus gen. et sp. nov., Masculuconus curvativus gen. et sp. nov., Helcionella bellus sp. nov., Igorella minuta sp. nov., Tubatoconus yuluensis gen. et sp. nov. and Striatoconus sp. This paper shows that the early monoplacophoran molluscs had reached at a relatively high diversity of genera and species and, therefore, indicates that the ancestor of the Mollusca might have appeared in Precambrian. It is stressed that shell morphology, muscular scar, morphological function and microstructure should be used for identification of the Monoplacophora.