江西乐平、瑞金早二叠世栖霞组的Cystomichelinia和Protomichelinia

CYSTOMICHELINIA AND PROTOMICHELINIA FROM CHIHSIA FORMATION OF LEPING AND RUIJIN, JIANGXI

本文简述了江西乐平、瑞金早二叠世栖霞组Cystomichelinia和Protomichelinia的性质,与国内外有关的种进行了比较;通过分析这两属的内部构造说明它们之间的关系;根据珊瑚体的壁刺发育与否、床板生长密度、体径大小及体壁厚度等特征,拟立了该两属的种的鉴别表;描述了7种,其中4新种和1新亚种。

The Tabulata dealt with in this paper were obtained from the Early Permian Chihsia Formation of Leping and Ruijin Counties, Jiangxi Province, including 4 species (with 3 new species) of Cystomichelinia and 3 species (with 1 new species) and 1 subspecies of Protomichelinia. The Cystomichelinia-bearing Chihsia Formation in Mt. Liyu of Leping can be divided in ascending order into 2 limestone beds, with their fossils indentified as follows: Bed. 7. Tabulata (Loc. No. F06): Cystomichelinia vesiculasa King, C. michelinioidea sp. nov., C. sublaibinensis sp. nov. and C. sp. 10.Sin Bed 4. (Loc. No. F01) Cystomichelinia jiangxiensis sp. nov. 25.94m According to the vertical distribution of the Tabulata, only one assemblage may be recognized, i.e., the Cystomichelinia jiangxiensis-C. michelinioidea Assemblage. Cystomichelinia is widely distributed in the lower part of the Chihsia Formation in South and Southwest China, forming the lower Chihsia Formation assemblage of Chaoxian county, Anhui province (Qi and Chen, 1982). The species C. biknia Fl(?)gel, 1964 can be found in the Lower Permian Ruteh Limestone of North Iran. The Chihsia Formation of Mt. Baiyun, Ruijin is about 117m in thickness, consisting of dark thick-bedded limestone with cherty nodules, yielding Protomichelinia abnormis markamensis Deng, P. ruijinensis sp. nov. and P. lepingensis poriferum subsp, nov. Among them, P. abnormis markamensis Deng is known to occur in the lower Lower Permian Mangcuo Formation of Markam, eastern Xizang (Deny and Zhang, 1984); P. ruijinensis sp. nov. closely resembles P. xinchengensis Lin, 1963 of the Chihsia Formation from Guangxi; P. lepingensis poriferum subsp, nov. bears a close resemblance to P. lepingensis Zhu, 1984 of the Chihsia Formation from Leping, Jiangxi, indicating an early EarIy Permian age of these members. Besides, Protomichelinia has also been known from the Lower Permian of Japan (Minato, 1955), USSR (Rushencev, Sarycheva, 1965), Turkey and Iran (Fl(?)gel, 1955, 1964). In the outline of corallum, Cystomichelinia is very similar to Protomichelinia, but differs in having peripheral vesicles. However, some members of the former have very rare peripheral vesicles and are almost similar to the latter, such as C. equitabulata Ting, C. muhispinosa King, C. vesicata Chen et Qi, C. simplex Deng et Zhang and C. michelinioidea sp. nov. In the structures of peripheral vesicles and tabulae, Cystomichelinia is mote complex than Protomichelinia. In the growth time, the former is shorter than the latter. Both Cystomichelinia and Protomichelinia are composed of numerous cerioid corallites which form a fan-shaped structure. Their larvas grow among the walls of adjacent corallites; this is why the larger and smaller corallites are mixed together on the same transveral section. So far, there have been found 27 species and subspecies of Cystomichelinia and 44 species and subspecies of Protomichelinia in the Lower Permian. The key to the identification of the species and subspecies of Cystomichelinia and Protomichelinia lies in the development of septal spines, density of tabulae, size of corallites and thickness of walls (Tables Ⅰ, Ⅱ). Description of new species and subspecies Cystomichelinia jiangxiensis sp. nov. (Pl. Ⅰ, figs. 2a—e) Cofallum massive, fan-shaped, measuring 27mm in width and 25mm in height, composed of polygonal corallites which are 2.6mm in size. Internal walls averagely 0.35mm in thickness. Wall pores rare. Septal spines very closely developed. Peripheral vesicles continuous, arranged in 1—2 rows. Tabulae arched or anastomosed, with 8—10 of them occupying a space of 5mm. Remarks In the thickness of internal walls and the density of tabulae, this species is similar to Cystomichelinia multicystosa spinosa Yang, 1978, but the latter has smaller corallites. Horizon and Locality Lower Permian Chihsia Formation; Mr. Liyu, Leping, Jiangxi. Cystomichelinia sublaibinensis sp. nov. (Pl. Ⅱ, fig. 2a, b) Corallum massive, fan-shaped, 20mm in width and 15mm in height, composed of polygonal corallites averagely 0.3mm in thickness. Wall pores undeveloped while septal spines very developed. Peripheral vesicles discontinuous and usually thickened, arranged in 1 row. Tabulae complete and arched or incomplete and anastomosed, with 8—10 of them occupying a space of 5mm. Remarks This species is similar to Cystomichelinia laibinensis Lin, 1963, but the latter has thinner internal walls and fine septal spines. Horizon and Locality Same as the preceding species. Cystomichelinia michelinioidea sp. nov. (Pl. Ⅱ, figs. 1a—c) Corallum massive, fan-shaped, 65mm in width and 55mm in height, composed of polygonal corallites averagely 4.1mm in size. Internal walls averagely 0.1mm in thickness. Wall pores developed. Septal spines and peripheral vesicles rare. Tabulae usually anastomosed and rarely arched, with 8—9 of them occupying a space of 5mm. Remarks This species is similar to Cystomichelinia massifascicula Xu (Jia et al., 1977), but the latter has discontinuous peripheral vesicles, smaller corallites and thinner internal walls. Horizon and Loeality Same as the preceding species. Protomichelinia ruijinensis sp. nov. (Pl. Ⅳ, figs. 2a, b) Corallum massive, fan-shaped, measuring 5mm in width and 4mm in height, composed of po- lygonal corallites averagely 5.5mm in size. Internal walls averagely 0.3mm in thickness. Wall pores developed, 0.2—0.3mm in diameter. Septal spines undeveloped. Tabulae horizontal or arched, with 4—6 of them occupying a space of 5mm. In larva stage, tabulae forming vesicles in shape. Remarks This species is similar to Protomichelinia xinchengensis Lin, 1963, but the latter has thinner internal walls and horizontal tabulae of larvas. Horizon and Locality Lower Permian Chihsia Formation; Mt. Baiyun, Ruijin, Jiangxi. Protomichelinia lopingensis poriferum subsp, nov. (Pl. Ⅳ, figs. 3a—c) Corallum massive, irregularly fan-shaped, 30mm in width and 25ram in height, composed of polygonal corallites averagely 2.4mm in size. Internal wails averagely 0.2mm in thickness. Wall pores developed. Septal spines developed and thickened. Tabulae horizontal or arched, with 8—9 of them occupying a space of 5mm. Remarks This species is similar to Protomichelinia lopingensis Zhu, 1982 in the development of septal spines and the density of tabulae, but differs in the numerous wall pores. Horizon and Locality Same as the preceding species.