江西宜春新塘早二叠世茅口组的四射珊瑚

EARLY PERMIAN MAOKOU FORMATION RUGOSE CORALS FROM XINTANG, YICHUN, JIANGXI

江西二叠纪珊瑚化石,最早由Grabau在1928年记载过1种即Tachylasma lopingense Grabau,产自江西乐平上二叠统。1931年和1937年,计荣森描述过4属4种及1亚种,它们是产自江西永新下二叠统的Allotropiophyllum grabaui Chi(应为Paracaninia grabaui),Paracaninia sinensis Chi, P. sinensis kaoi Chi, Tachylasma yungsinense Chi及Timorphyllum gerthi Chi(应为Kinkaidia gerthi)。1982年,陈华成等编著的华东地区古生物图册,记载了江西二叠纪珊瑚3属5种,它们是产自江西瑞昌茅口组的Ipciphyllum

This paper deals with the rugose corals obtained from the Lower Permian Maokou Formation of Xintang, Yichun, Jiangxi, including 4 genera, 4 species and 3 indeterminate species.The rugose coral-bearing Maokou Formation in this region can be divided in ascending order into the following 3 limestone beds.Bed 4 Dark-grey, thick-bedded massive limestone containing cherty nodules, with the coral Timorphyllum raphiseptatum sp. nov. (XF-32) 5.18 mBed 3 Dark-grey, thick-bedded massive carbonacerous limestone with the coral Timorphyllum multiseptatura sp. nov. (XF-29) 15 mBed 2 Grey and light grey thick-bedded massive limestone, with the corals Allotropiophyllum sulciforme sp. nov., Pseudohuangia sp. A, P. sp. B, P. sp. C, Ipciphyllum asperurn sp. nov. and I. subtirnoricum (Huang) (XF-16, 14, 8) 14.52mBased on the vertical distribution of rugose corals, 1 assemblage may be recognized, namely, the Ipciphyllurn asperum-Pseudohuangia-Timorphyllum multiseptatum Assemblage, which contains lpciphyllum subtirnoricurn (Huang), I. asperum sp. nov., Pseudohuangia sp. A, P. sp. B, P. sp. C, Allotropiophyllum sulciforme sp. nov., Timorphyllum multiseptatum sp. nov. and T. rephiseptatum sp. nov. Among these corals, Ipciphyllum is rather rich in individual and widespread in the Maokouan of S and SW China; Pseudohuangia usually was found in the Chihsia Formation in S China, but it also can be seen in the Maokou Formation of Jiangyou, Sichuan and in the Neoschwagerina zone of Laos; Allotropiophyllum usually occurs in the Maokouan of S China and in the Lower Permian of Alpen; while Timorphyllum is known to occur in the Maokou Formation of China, and also in the Permian of Timor and Lower Permian of USSR. This assemblage may be compared with the Ipciphyllurn subtimorcum zone of S China (Huang, 1932) and the Ipeiphyllum huangia-Allotropiophyllum proceriseptatum assemblage of Beichuan and Jiangyou of Sichuan, China (Zhao, 1981), but the latter contains more members of corals.The massive coral Ipciphyllum made its earliest appearance, with Ipciphyllum asperurn appearing earlier than Ipciphyllum subtimoricum; then the fascicular corals Pseudohuangia, with Pseudohuangia sp. C appearing earlier than Pseudohuangia spp. A and B, and lastly, the solitary corals Allotropiophyllum and Timorphyllum. The dominance of corals for the first time is known to occur in late Early Permian. Generally, the massive corals Ipciphyllum inhabited an ecological environment of slightly shallow water with a high energy; the fascicular corals, an ecological environment of slightly deeper water with a slightly higher energy; and the solitary corals, an ecological environment of deeper water with a lower energy. As compared with Ipciphyllum subtimoricum, Ipciphyllum asperum has thickened interwalls and septa. And, as compared with Pseudohuangia spp. A and B, Pseudohuangia sp. C also has thickened walls and septa. In the solitary corals Allotropiophyllurn and Timorphyllum, the bodies are very small; the septa are longer, extending to the center to form interwall, or with the counter septum extending to the center of corallite to form median columella. It follows that in the late Early Permian of this region, the seawater changed from shallower to deeper and the energy from higher to lower.Description of New species Timorphyllum raphiseptatum sp. nov. (P1. Ⅰ, fig. 7; P1. Ⅱ, fig. 3)Diagnosis: Septa needle-like.Description: Solitary corallite 10.5 mm in diameter. Sepia of two orders, 36+36 in number, needle-like in shape, with formula of arrangement recognized as (?). Major septa extending to the periphery of axis; minor ones about 1/4—1/3 as long as the major ones. Cardinal septum nearly as long as the minor ones; counter Septum thickened and extending to the center, forming columella which is thickened and twiglike in shape.Remarks: This species is similar to Timorphyllum wanneri Gerth, 1921, but in the latter, the major sepia are numerous, shorter and thinner, and the minor ones are underdeveloped.Horizon and locality: Bed4, Maokou Formation, Lower Permian; Xintang, Yichun, Jiangxi.Timorphyllum multiseptatum sp. nov. (P1. Ⅰ, gigs. 5, 6; P1. Ⅱ, fig. 5; Text-fig. 2)Diagnosis: Septa numerous.Description: Solitary corallite elliptical in outline, 13×17.5 mm. Septa of two orders, 41+41 in number, with formula of arrangement recognized as (?). Major septa long, straight, with ends flexuous or slightly thickened; minor ones straight, needlelike, about 1/4—1/3 as long as the major ones. Cardinal septum slightly shorter than minor ones; counter septum longer, thickened and extending to the center to form columella which is 1.2 mm in diameter.Remarks: This species may be compared with Timorphyllum raphiseptatum sp. nov., but the latter has less numerous sepia, smaller diameter of corallite and wider columella.Horizon and locality: Except bed_3 same as preceding species.Allotropiophyllum sulciforrae sp. nov. (P1. Ⅰ, fig. 1; P1. Ⅱ, fig. 4) Diagnosis: Interwall trough-like in shape.Description: Solitary small corallite elliptical in outline, 2.8 ~ 2.3 mm in diameter; outer wall thin. Septa of two orders, 16+16 in number. Major septa extending to axis, with their ends connected with trough-shaped interwall, 2.3 mm in length and 0.4 mm in width; minor ones about 1/3 as long as the major ones. Cardinal septum nearly as long as the minor ones.Remarks: This species is similar to Allotropiophyllum proceriseptatum Zhao, 1981, but in the latter, the corallite has a greater diameter, the septa are more in number and the interwall is herringbone in appearance.Horizon and locality: Bed 2, Maokou Formation, Lower Permian; Xintang, Yichun, Jiangxi.Ipciphyllum asperum sp. nov. (P1. Ⅰ. fig. 8; P1. Ⅲ, figs. 1—4; Text-fig. 3)Diagnosis: Interwalls coarse in appearance.Description: Corallum massive, composed of numerous irregularly polygonal corallites 4.5—8 mm in diameter; distance between centers of two adjacent corallites about 4—7 mm; interwalls coarse, flexuous, about 0.1—0.2 mm in thickness. Septa (14—18)+(14—18) in number. Major septa thinner in dissepimentarium and thickened in the tabularium, with their ends extending to the axis, almost connected with syncolumella; minor ones about 1/3—1/2 as long as the major ones. Dissepiments irregularly herringbone, concentrical, cystiform or long-arcuate in arrangement. Syncolumella 1.2—1.8 mm in diameter, composed of shorter, thin median plate, a few discontinuous radial lamellae and incomplete annulated or arched tabellae.In longitudinal section, the cystosepimentarium composed of cystosepiments unequal in size. Clinotabulae developed; tabularium narrow, consisting of tabulae slightly horizontal and concave or inclined, with 18—20 of them occupying a distance of 5 mm.Remarks: In the thickness of interwalls and number of septa, this species is similar to Ipciphyllum baishagouense Fan, 1978, but in the latter, the interwalls are regular and thickened, becoming serrate in shape, the median plate is thickened and the tabulae are less numerous.Horizon and locality: Same as the prec ding species.