中国空谷期—罗德期菊石壳的形态发育史及其在国际对比中的意义  

EVOLUTIONARY HISTORY OF AMMONOIDS ACROSS THE EARLY- MIDDLE PERMIAN BOUNDARY IN CHINA AND ITS IMPLICATIONS FOR GLOBAL CORRELATION

作　　者：牟林[1] 

机构地区：[1]中国科学院南京地质古生物研究所,江苏南京210008

出　　处：《古生物学报》2013年第4期459-466,共8页Acta Palaeontologica Sinica

基　　金：国家自然科学基金项目(41002005;41290260);中国科学院战略性先导科技专项(B类)(XDB03010102)资助

摘　　要：基于一些业已报道的中国Kungurian期至Roadian期界线附近的菊石材料(26个属,48个种),对其进行壳的形态空间分析,发现空谷期菊石在形态空间上主要分为三个类型:1)旋环重叠程度D=0—0.1,旋环膨胀速率W=1.5—2.5,代表Saunders等(2004)的A类型;2)D=0—0.1,W=3,代表F类型;3)D=0.05—0.15,W=4—5,与F类型相比较,具有较大膨胀速率。相对应的罗德期菊石主要可以分为两个类型:1)D=0.1—0.25,W=1—2,代表A类型;2)D=0.4—0.6,W=1—2,代表C类型。从壳的形态发育史来看,空谷期到罗德期总体趋势是连续的,并没有受到外界大的干扰,同时也发生了明显的变化(罗德期形态空间明显占据了更广阔的位置,代表了菊石演化的新方向),壳不仅变得更加外卷,壳的膨胀速率也有所减小,比如,空谷期存在的膨胀速率较大的第三种类型在罗德期中并未发现。这一趋势在全球早—中二叠世菊石壳D-W等密度图中同样反映出来,说明尽管空谷期—罗德期这一时间段我国存在较多地方性属种(以其特殊的壳饰与缝合线为特征),在国际对比中难以应用,但是从壳的形态发育特征来说,与其它地区对比具有潜在的意义。This study is based on ammonoid records repor morphological analysis bas the Kungurian-Roadian ted from China. A ed on Raup＇s （1966）method was used to analyze the evolutionary history of shell morphology of ammonoids. Three parameters are referenced： whorl expansion rate （W=（d/e）^2）, whorl overlap degree （D=c/d）, and the shape of the whorl cross-section （S=b/a）. These parameters have adaptive significance because they determine a number of hydrostatic and hydrodynamic parameters of the shell. Ammonoid shell morphospace analysis indi- cates that the Kungurian ammonoids morphospace is divided into three main types. Type 1 has D value between 0-0. 1 and W rate between 1. 5- 2.5 which is consistent with Type A of Saunders. Type 2 with D = 0-0. 1 and W = 3 is generally consistent with F type of Saunders. Type 3 with D =0. 5-1. 5 and W=4-5, is comparable with F type, but has a larger W value. Roadian ammonoids morphospace could be divided into two types： One has, D between 0. 1-0. 25 and W between 1-2 representing A type; another has D between 0.4-0.6, W between 1-2, representing C type. In terms of morphospace, the general trend from Kungurian through Roadian is transitional, suggesting no major external interruptions. How- ever, the morphospace had also undergone a signi- ficant change. There is an obvious a space of mor- phological broader position occupied in Roadian, representing a new direction in evolution, in which the shell is not only more evolute, but the shell ex- pansion rate is also decreased. The same trend is also reflected globally in the Early Permian-Middle Permian ammonoid shell D-W density contours. This indicates that in spite of more endemic species from Kungurian to Roadian in China, which are difficult to be applied for international correlation, it can be compared with those in other regions of the world from the morphospace point of view.

关 键 词：菊石 形态空间 空谷期 罗德期 

分 类 号：Q915[天文地球—古生物学与地层学]