秦岭中泥盆世西汉水群中的几种四射珊瑚化石

SPECIES OF RUGOSE CORALS FROM XIHANSHUI GROUP OF QINLING MTS.

本文描述了产自北秦岭中泥盆统西汉水群上部的10属12种四射珊瑚化石,包括3新种。由于其中出现了Temnophyllum waltheri, Grypophyllum tenue, Tabulophyllum annulatum和Disphyllum hsianghsienense等德国、苏联和我国南方Givetian阶的常见分子,因此,甘肃宕昌产上述珊瑚化石的地层时代应属于中泥盆世晚期。本文还根据笔者对保存在加拿大和德国等地自然博物馆中某些珊瑚属模式标本的观察和重新研究,讨论了一些珊瑚属种之间的亲缘关系并厘订了某些属征。

The Qinling fold system embraces a vast mountainous country extending for about 1000 km, with a maximum width of 250 km. The Devonian of Qinling occurs in two regions, which may be designated by the names of northern and southern Qinling regions, each with a distinct geological development. There are practically no Lower Devonian deposits in the northern Qinling region; the Middle Devonian is composed of carbonate and detrital rocks of neritic marine facies; while the Upper Devonian continental red beds are most widely distributed. More complete Devonian sections represented by all of the three series are found in the southern Qinling region. The rugose corals described and illustrated in the present paper were collected by the Regional Geological Survey Team of Gansu from the Xihanshui Group in Dangchang county, Gansu province (belonging to the northern Qinling region), comprising 11 species in 9 genera, namely: Cystiphylloides fraternus (Wedekind et Vollbrecht); Cystiphylloides secundum (Goldfuss); Disphyllum of. hsianghsienense Yoh; Grypophyllum tenue Wedekind; Sinodisphyllum litvinovitshae (Soshkina); Sinodisphyllum sp.; Synaptophyllum dangchangense sp. nov.; Tabulophyllum annulatum (Wang); Truncicarinulum? sp.; Thamnophyllum xiaoyigouense sp. nov. and Zelophyllia? gansuensis sp. nov. Among them, Temnophyllum waltheri, Grypophyllum tenue, Tabulophyllum annulatum and Disphyllum hsianghsienense are characteristic of the Givetian in South China, U.S.S.R. and Germany. Since the corals have rarely been reported from the Xihanshui Group of the Qinling Mts., a brief description of these fossils seems desirable. Description of New Species Synaptophyllum dangchangense sp. nov. (Pl. Ⅰ, figs. la, b) Loose phaceloid corals with cylindrical corallites, about 8mm in diameter. Epitheca 0.2—0.6mm thick. Major septa rather long, with some of them extending to the axis, numbering 27. Septa strongly thickened in basal portions by deposit of stereolasma. Minor septa very short or rudimental. Tabulae complete, horizontal or concave axially and downward turned peripherally. Dissepiments absent. Remarks This new species differs from the type species of the genus in its larger corallites, rudimental minor septa and the shape of tabulae. Zelophyllia? gansuensis sp. nov. (Pl. Ⅰ, figs. 14—16) Corallite solitary, 8—10mm in diameter. Septa of two orders, numbering (21—24)×2. Major septa long, extending to the axis. Minor septa about 1/2 to 2/3 as long as the major ones. Stereozone 1.0—1.5mm thick. Tabulae distinct, 2mm apart. No dissepiments present. Remarks The present new species differs from Zelophyllia tabulata (Soshkina) in its smaller solitary corallite, longer septa and thicker stereozone. Thamnophyllum xiaoyigouense sp. nov. (Pl. Ⅲ, figs. 1—4) Phaceloid or dendroid corals with cylindrical corallites, averaging 4.5—5.5mm in adult diameter. Adjacent corallites 2mm apart or in lateral contact. Major septa rather short, not extending to the axis but leaving a considerably wide axial space, numbering 14—16. Minor septa very short, terminating at the inner margins of the dissepimentarium. Sclerotheca distinct. Dissepirnentarium consisting of one row of flat dissepiments and one row of horseshoe dissepiments. Tabulae complete and flat. Remarks This new form differs from Thamnophyllum stachei in its smaller diameter and less septa.