广西合山的二叠纪纹窗贝

Permophricodothyris OF HESHAN, GUANGXI

本文研究的二叠纹窗贝标本采自广西合山上二叠统合山组中下部深灰色含泥质生物碎屑灰岩,在串管海绵富集层位之上。二叠纹窗贝(Permophricodothyris Pavlova)从巴夫洛娃(1965)发表以来,除在泰国(Grant,R.E., 1976)和巴基斯坦(Waterhouse,J.B.and Sangat Piyasin,1970)有过报导外,中国境内这是首次报导。此属的特征是“腕螺的尖端指向铰合缘,螺环数多,可达28个,腕棒长达壳长的3/4,齿板及中隔板缺失;在生长层上微壳饰双筒型刺。”广西发现的为一新种广西二叠纹窗贝(新种)Permophricodothyris guangxiensis(sp.nov.)长大的腕螺指向铰合缘;主突起,中叶卵形凹坑,侧叶为微向两侧长瘤状突起,腹三角孔明显,有清淅的孔缘脊,无齿板和中隔板。对与之有关的Neophricadothyris和Squamularia等属的特征作了讨论,认为Neophricadothyris为Phricodothyris的同义名应废除,Squamularia的腕骨构造有待进一步研究,微细壳饰定属欠确切。

The specimens of Permophricodothyris guangxiensis sp. nov. collected from dark grey argillaceous bioclastic limestone of Lower Heshan Formation, Heshan,Guangxi. Since Pavlova,E. E. (1965) studied Permothricodothyris Pavlova for the first time, apart from some discoveries from Thailand (Grant,R. E., 1976) and Pakistan(Waterhouse, J. B. and Sangat Piyasan, 1970),this paper is first report in China. The diagnoses of this genus are 'the points of spiralia which directed at hinge margin; Spiralia with 28 coils; Crura with 3/4 of tenth of shell; complete absence of dental plates or median septa; the microshell double-barrelled thorns on growth lamella. But the Permophricodothyris found in Guangxi is a new species: Permophricodothyris guangxiensis. It is characterized by the grown-up spiralia which point at hinge margin; the projection on the subelliptical hollow in the middle lobe; the node-shaped projections obliquely towards two sides in lateral lobes; the obvious ventral sulcus; the obvious aperture ridge, complete absence of dental platal and median septa.The Characteristics of Neophricadothyris and Squamularia which are related to it are studied, it should be abolished that Neophricadothyris is considered to be the synonym of Phricodothyris;the structure of spiral bones of Squamularia must still be further studied, it is not always accurate to define genus by microcrust-decorations.