南丹相泥盆系中的翼口蛤类

ON DEVONIAN PTEROCHAENIINS (BIVALVIA)

系统描述了湖南泥盆系的翼口蛤类标本,共5种(或亚种),其中1新种.并对国内外已发表的材料作了系统整理和厘订,指出耳部特征在此类标本研究中的重要意义.据此提出新的分类方案,建立1新亚科 Pterochaeniinae(subfam. nov.)和1新亚属 Pterochaenia (Clarkea)(subgen. nov.).为便于鉴定,还编制了检索表.

Pterochaenia and suchlike are widespread and well abundant in the Devonian rocks of plankton biofaces. Since they are not well-known, this study concentrates on their systematics, dealing with 5 species and subspecies, including l new species. A new subfamily Pterochaeniinae is erected for them within the family Lunulacardiidae, with Clarkea proposed herein as a new subgenus of Pterochaenia. Superfamily Ambonychiacea Miller, 1877 Family Lunulacardiidae Fischer, 1887 Subfamily Pterochaeniinae nov. Type genus: Pterochaenia Clarke, 1904 (p. 247), designated herein as the type genus of the new subfamily. Description: Shell small and tenuous, equivalve, inequilateral, opisthodetic, with prosogyre beaks; well-defined anterior ear separated from the body of the shell by a deep groove, flange-like or triangular in form; surface with concentric ornament, sometimes with fine internal costellae; a large byssal gape present; internal features unknown. Remarks: This subfamily differs from the Lunulacardiinae in having a prominent anterior groove which separates the anmrior ear from the body of the shell, and in lacking the flattened lunule characteristic of the latter. It is believed that the morphology of the anterior ears is highly important to the classification of pterochaeniins. The suggested taxonomic distribution of Pterochaeniinae is as follows: Genus Pterochaenia Clarke, 1904 P. (Pterochaenia) fragilis (Hall) (Clarke, 1904, p. 249, pl. 5, figs. 1-10) fragilis orbicularis Clarke (1904, p. 252, pl. 4, figs. 17, 18; pl. 5, figs. 11-16) sinuosa Clarke (1904, p. 253, pl. 5, figs. 17-22) tschernyschewi Zamjatin (1911, p. 8, p. 24; pl. 1, figs. 14, 15) nandanensis Zhang et Zhao (1986, p. 397, pl. 1, figs. 12-23) (=P. fragilis by the same authors in the same paper, p. 396, pl. 1, figs. 8-10) P. (Clarkea) subgen, nov. cashaquae Clarke (1904, p. 254, pl. 4, figs. 0-25) (=Pterochaenia uchtensis Clarke, 1904) elmensis Clarke (1904, p. 254, pl. 4, figs. 26, 27) perissa Clarke (1904, p. 253, pl. 4, fig. 19) maraellensis (Clarke) (1904, p. 266, text-fig. 12) timanica Zamjatin (1911, p. 7, pl. 1, fig. 13) insidiosa (Barrande) (1981, pl. 230, IV, figs. 1-26) (=Posidonia hians Waldschmidt, 1885) Genus Guangxiconcha Zhang, 1977 hechiensis Zhang(1977, p. 492, pl. 193, figs. 1-3)Modiomorpha convexa Zhang et Zhao, 1986, p. 399, pl. 1, figs. 27, 29-33)Modiomorpha costata Zhang et Zhao, 1986, p. 399, pl. 2, figs. 8-11, 13, 14) zhuzhouensis sp. nov. ?Genus Joachyraia Ruzicka, 1949 falcata (Barrande) (1881, pl. 245, IV, figs. 9-28) chelmiensis (Korejwo et Teller) (1964, p. 247, pl. 6, figs. 2-7; text-fig. 13) tenuis (Korejwo et Teller)(1964, p. 248, pl. 6, figs. 8-12, text-fig. 14) Distribution: Asia, Europe and North America; Upper Silurian-Devonian. Key of identification: 1. Posterior ear well-developed, with a spur at the end Joachymia 1. Posterior ear not well differentiated 2. Anterior ear rounded triangular, extending anterodorsally Guangxiconcha 2. Anterior ear flange-formed, extending along byssal margin, obtusely truncated at the end Pterochaenia 3. Byssal margin short, forming an obtuse angle or a convex with the anteroventral margin P. (Ptcrochaenia) 3. Byssal margin long, nearly straight, with anterior ear extending dorsoventrally P. (Clarkea) Genus Pteroehaenia Clarke, 1904 Subgenus Clarkea nov. Type species: Pterochaenia cashaquae Clarke, 1904 Description: Shell small, arcuate or cresc nt, truncate anteriorly; byssal margin long, nearly straight, with anterior ear extending dorsoventrally, flange-formed, obtusely truncated at the end; posterior ear not well differentiated; surface with concentric ornament, sometimes with internal costellae. Etymology: The subgenus is named after Professor J. M. Clarke in memory of his contributions to the study of Naples fauna. Comparison: Clarkea differs from Pterochaenia (s. s.) in truncate anteriorly, with long and nearly straight byssal margin and dorsoventrally extended anterior ear. Distribution: Asia, Europe and North America; Middle Devonian-Upper Devonian. Genus Guangxiconcha Zhang, 1977 Type species: Guangxiconcha hechiensis Zhang, 1977 Guangxiconcha zhuzhouensis sp. nov. (Pl. I, figs. 15-18; text-fig. 3) Description: Shell small, moderately inflated, suboval, higher than long with H/L ratio of about 1.5; anterior ear large, triangular, acute, extending upwards high beyond the hinge, separated from the body of the shell by a deep groove; posterior ear slightly differentiated, narrow and depressed; surface only with faint concentric growth lines. Compxrisou: The described species differs rom G. hechiensis in the smaller size, higher than long, and the gentle surface of anterior ear. Occurrence: Lower Shetienchiao Formation, Upper Devonian (Frasnian); Baimalong of Zhuzhou, and Pingshang of Xinshao, Hunan, China. Acknowledgements: The authors are much obliged to Dr. 3. Kriz of the Geological Survey in Praha, Czechoslovakia for providing the important paper of Dr. Ruzicka formerly not accessible in Nanjing.