秀山湾兰多维列末期胞石成种与特型  

END LLANDOVERY CHITINOZOAN SPECIATION AND SPECIALIST OF THE XIUSHAN BAY

作　　者：耿良玉[1] 

机构地区：[1]中国科学院南京地质古生物研究所

出　　处：《微体古生物学报》1997年第4期357-377,共21页Acta Micropalaeontologica Sinica

基　　金：国家自然科学基金委员会基金;中国科学院南京地质古生物研究所现代古生物学和地层学开放实验室基金;中国科学院南京地质古生物研究所与中国科学院古脊椎与古人类研究所专项基金

摘　　要：特型包括形态特型和大小特型。特型是特殊环境的产物。随着温度上升、海水粘度下降，迁入并被隔离于温（盐）跃层内的Ａｎｇｏｃｈｉｔｉｎａｌｏｎｇｉｃｏｌｉｓ产生成种作用。Ｌａｍｂｄａｃｈｉｔｉｎａｂｉｐｅｄａｔａ和Ｌ．ｓｙｎａｐｈａｃａｎｔｈａ减少体积、增加表面积而上浮；Ａｎｇｏｃｈｉｔｉｎａｓｐ．增加体积而下沉：各自开发空生态灶。前者采取了ｒ策略，后者采取Ｋ策略。本文支持胞石是后生动物卵的卵囊的观点，认为：侏儒是按发育程序，但提前孵化的卵的卵囊，巨型是直接孵化（超期孵化）的卵的卵囊。Ａ．ｓｐ．的形态改变通过细胞分裂超期和加速而实现。成种作用产生的新生分子的形态和大小为空生态灶的容量和位置所渠导，具有明显的方向性。Since punctuated equilibria was proposed by Eldrege and Gould (1972) as an alternative to phyletic gradualism,much of the conflict concerning its validity has been promoted by friends or foes.The crux of the matter is the evidence.Gingerich's (1984) compendious words are worth recalling,“Punctuated equilibria——where is the evidence?”.It is hardly conceivable to endorse punctuated equilibria as an alternative mode to gradualism without supportable evidence about the nature of evolution in geographically isolated peripheral populations.In this paper fulfilled as part of the project of Silurian chitinozoans from the Yangtze Region,we will provide evidence of chitinozoan populations of this kind and of allopatric speciation taking place within an interval of ca.0.009m.y.(burst of rapid change).Following branching speciation,the novelties remained in morphological stability for about 1.7—5.1m.y.(long term stasis). Our conclusion is as follows: 1.The Xiushan Bay,which gets its name from the Xiushan Fauna that lived in the region near the Equator in the latest Llandovery,with a palaeomagnetic latitude of 6.8°N (Opdyke et al.,1986,see Lin,1987,1989).It was a semi closed inland bay which would have had,on the analogy of the South China Sea,especially the Malacca Strait,a diluted salinity of less than 31‰.Its maximum depth of water in which BA3 brachiopods inhabited was approximately 66m(Boucot,1975;Rong et al.,1984;Johnson,1987) and its permanently stratified water column was supposed to be composed of an upper 30m thick uniform layer and a lower 26m thick thermocline.Laterally,there existed a salinity gradient in the bay from the Yongshun Estuary (Wang,1996) to the Jiangling Strait.An exotic water mass form the Yangtze Sea,a marginal sea,entered through the strait and flowed along the coasts of the bay as a drift current above the thermocline. 2.The chitinozoan species Angochitina longicollis ,which originated from the Osel Island of W.Estonia at the turriculatus/crispus graptolite zone time (B

关 键 词：胞石 卵 特型 异域成种 微体古生物 

分 类 号：Q913.2[天文地球—古生物学与地层学]