浙西江山晚奥陶世三分贝族—新属——Costitrimerella

COSTITRIMERELLA, A NEW GENUS OF TRIMERELLOID BRACHIOPOD FROM HUANGNEKANG FORMATION(EARLY ASHGILL), JIANGSHAN, WESTERN ZHEJIANG, EAST CHINA

Costitrimerella gen. nov. 属于无铰纲腕足动物中的三分贝族.模式种Costitrimerella costellata gen. et sp. nov. 的模式标本采自浙江江山城西约5km的坛二村北和(土弄)里上奥陶统黄泥岗组的硅质结核中.因发育良好放射状壳线、背肌台前部强烈高隆又缺失台穹构造而与本族其它15属(壳表均光滑仅饰同心生长线纹)有重要的差别,它可能代表奥陶纪晚期三分贝族的一个奇特支系.志留纪三分贝族大都被认为是浅水产物.江山黄泥岗组紫红色泥岩中含深水的叶月贝(Foliomena)腕足动物群,但未寻获三分贝族化石,而夹于泥岩中的硅质结核未见叶月贝动物群的成员,却产三分贝族的代表,其生存环境尚待深入探查.

Trimerelloids are peculiar fossil inarticulate brachiopods, usually large forms with thick calcareous shells and a well developed and complicated muscle system. They range from the Middle Ordovician to Ludlow Series of Silurian. In the T eatise on the Invertebrate Palaeontology Part H (Brachiopoda), only five genera were recognized by Rowell (1965) for the Superfamily Trimerellacea Davidson et King, 1872. They are Trimerella Billings, 1862; Dinobolus Hall, 1871; Eodinobolus Rowell, 1963; Monomerella Billings, 1871; and Rhynobolus Hall, 1871. All of these genera are of Silurian age with the exception of Eodinobolus which is Middle-Late Ordovician. However, Li and Han (1980) and Li (1984) have since described seven new genera of trimerelloid with twelve new species from the Huangnekang Formation (early Ashgill, Late Ordovician), Jiangshan, western Zhejiang, east China. Li and Han (1980) erected Palaeotrimerella, Sinotrimerella, Machaerocolella, Funzuella, and Paradinobolus, and Li(1984)established Prosoponell and Selenella. Later Li (1985) proposed Gyroselenella to replace Selenella Li since the latter was pre-occupied by the Devonian brachiopod Selenella Hall and Clarke, 1893. Niki in and Popov (in Klenina and others, 1984) proposed Ovidiella with the type species Ovidiella plana Nikitin and Popov from the Bestamakskaia svita (Middle Ordovician) of Chingiz, Kazakhstal. Popov and Rukavishnikova (1986, p.38) established Adensu with the type species A. monstratum Popov and Rukavishnikova, 1986 from Dulankariskii, Gorizont (Upper Ordovician), Chu-Ili Mountains, Southern Kazakhstan. Zeng(in Wang and others, 1987)proposed Yidurella with the type species Yidurella yiduensis Zeng from the upper Shamao Formation (late Telychian, Late Llandov ry), Maohutang, Yidu, Western Hubei, Southwest China.