论晚二叠世的“克氏蛤”  

ON "CLARAIA" (BIVALVIA) OF LATE PERMIAN

作　　者：方宗杰[1] 

机构地区：[1]中国科学院南京地质古生物研究所,南京210008

出　　处：《古生物学报》1993年第6期653-661,793,共9页Acta Palaeontologica Sinica

摘　　要：系统评述了目前世界上已发现的晚二叠世克氏蛤类标本,并描述采自贵州、云南、藏东的有关化石1属3种,其中1新属1新种.右壳足丝凹口特征在克氏蛤类研究中具有重要意义.晚二叠世的Claraioides gen.nov.以足丝凹口内端明显向腹方或后腹方扩展膨大成足丝凹湾而不同于早三叠世的Claraia.后者似由前者演化而来,它们在二叠-三叠系界线附近发生替代,可能与古生代末的绝灭事件相关.Quite a lot of Permian bivalves from different parts of the world have been included in the genus Claraia since 1977, such as Claraia bioni Nakazawa, 1977, Kashmir; ?C. posidoniformis Termier and Termier, 1977, Tunisia; C. ovosemelica Lobanova, 1979, Novaya Zemlya; C. caucasica Kulikov and Tkachuk, 1979, Northern Caucasus; C. primitiva Yin, 1982, Guangxi, China; and C. diana Guo, 1985, Yunnan, China. No ligament structure can be discerned from them except C. prirnitiva Yin. After reviewing the relevant Permian materials, the writer has come to a conclusion that no real Claraia occurred in the Late Permian. Unlike other species C. bioni Nakazawa occurring in the Permo-Triassic transitional beds of Kashmir may well represent a member of the genus Claraia and should be regarded as a 'Triassic type' form mixed with Permian relics. Here described are some new materials from Guizhou, Yunnan, East Xizang including a new genus Claraioides, two known species and a new species C. guizhouensis. It seems that the characters of byssal notch in the right valve are very important to the classification of Claraia and the like. Claraioides gen. nov. is characterized by the existence of a byssal embayment in the right valve indicating a strongly epibyssate habit, by which it may be distinguished from the comparable Claraia and Pseudoclaraia. Contrary to Yin's opinion that Claraia and the like of Late Permian and the earliest Triassic lived a pseudoplanktonic life (Yin, 1982, p. 342; 1987, p. 237), the characters of Claraia, Pseudoclaraia and Claraioides gen. nov. suggest that they were byssate epibenthic bivalves. All of them are provided with auricle-notch stabilization mechanism (Stanley, 1970, 1972), especially in Claraioides gen. nov., the byssus of which might be modified to become a calcified plug passing through embayment in lower (right) valve as in Anomia. Claraia was more active than Claraioides gen. nov. and probably evolved from the latter arising from the Permo-Triassic extinction event. (Text-fig. 1,

关 键 词：晚二叠世 足丝凹湾 克氏蛤类 化石 

分 类 号：Q915.817.4[天文地球—古生物学与地层学]