华南中-上泥盆统界线附近的秃嘴贝类腕足动物  

LEIORHYNCHID BRACHIOPODS ACROSS THE MIDDLE-UPPER DEVONIAN BOUNDARY IN SOUTH CHINA

作　　者：张美琼[1] 马学平[1] 张宇波[1] 

机构地区：[1]北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871

出　　处：《古生物学报》2015年第4期481-500,共20页Acta Palaeontologica Sinica

基　　金：国家自然科学基金重大项目(41290260)资助

摘　　要：小嘴贝类是中-上泥盆统界线附近的一类重要腕足动物,其中的秃嘴贝类是我国华南该界线附近双腔贝类-秃嘴贝类组合带的主要分子。Ypsilorhynchus Sartenaer,1970,Leiorhynchus Hall,1860以及Yocrarhynchus Sartenaer,1995是该组合带内具有代表性的三属。然而华南众多冠以Leiorhynchus的分子基本缺乏准确形态描述及地层分布资料,这使其地层分布及属性归属出现各种问题。本文系统描述采自华南三个剖面(湖南大坝口,四川龙门山,云南盘溪)包含中泥盆统上部—上泥盆统下部地层的秃嘴贝类,总计4属5种:Leiorhynchus kwangsiensis Grabau,Ypsilorhynchus globosus(Wang et al.),"Yp."subellipticus(Fang),Yocrarhynchus orientalis(Chen),Calvinaria sinensis(Fang)。对比讨论其中秃嘴贝亚科3属的主要外部形态及内部构造区别特征:Ypsilorhynchus壳线发育程度较好,分布始于壳体近喙部并覆盖整个壳体,数量也较多,腹壳内部齿板相互联合并与腹壳中隔板联合形成倒Y型结构,侧腔发育;Leiorhynchus壳线分布始于壳体中部,发育较弱,于侧区尤其微弱,壳内齿板分离、近平行或向腹方收敛直接融合于壳底,侧腔发育;Yocrarhynchus个体较小,壳线相对较宽,分布始于壳体后部,数量相对稀少,齿板向腹方强烈收敛,融合于壳底,侧腔狭窄。对上述材料的研究表明,华南弗拉阶下部确实存在Leiorhynchus,而产自云南盘溪剖面及附近的几个所谓的Leiorhynchus种则应归于其他不同属内,包括Ypsilorhynchus,Calvinaria等。华南的Leiorhynchus还可能包括L.obesus Grabau,确切的时代为弗拉阶下部,而众多其他所谓的Leiorhynchus分子应从该属中移除。Rhynchonellide brachiopods are an important group across the Middle-Upper Devonian boundary, of which leiorhynchids are predominant in the ambocoeliid-leiorhynchid Assemblage Zone at the boundary in South China. In this biozone, Ypsilorhynchus Sartenaer, 1970, Leiorhynchus Hall, 1860 and gocrarhynchus Sartenaer, 1995 are three characteristic genera. However, lack of detailed morphological description and stratigraphic data in the very numerous so-called Leiorhynchus of South China has posed various difficulties to clarify their classification and stratigraphic distribution. Four genera and five species of the Leiorhynchidae are described from three Givetian-Frasnian sections （Dabakou Section in Hunan, Longmenshan Section in Sichuan and Panxi Section in Yunnan）. They are Leiorhynchus kwangsiensis Grabau, Ypsilorhynchus globosus （Wang et al.）, ＂Yp.＂ subellipticus （Fang）, gocrarhynchus orientalis （ Chen ）, Calvinaria sinensis （Fang）, of which the former three genera of the Leiorhynchinae have been further investigated regarding their differences in external morphology and internal structure. Ypsilorhynchus can be distinguished by numerous well- developed costae, which start from near the beak and cover the whole shell; dental plates converge and join ventrally, supported by the ventral septum to form an inverted Y-shaped spondylium; umbonal cavities are distinct. Costae of Leiorhynchus appear at mid-length of the shell, which are weak, especially on the flanks; dental plates are sub-parallel or convergent ventrally to merge into the valve floor directly l umbonal cavities are distinct; Yocrarhynchus is comparatively small; costae are few and coarse, which originate from the posterior; dental plates are strongly convergent ventrally and can meet the valve floor; umbonal cavities are narrow. It is clear through our study that Leiorhynchus is present in the lower Frasnian in South China; several so-called ＂Leiorhynchus＂ species previously described from the Panxi section and adjacent areas s

关 键 词：小嘴贝类 秃嘴贝 一打得组 土桥子组 泥盆纪 湖南 四川 云南 

分 类 号：Q915[天文地球—古生物学与地层学]