湘中泥盆系弗拉阶顶部腕足动物种群统计及其古生态学意义  

POPULATION STATISTICS OF TWO LATE FRASNIAN(LATE DEVONIAN) BRACHIOPOD FAUNAS FROM CENTRAL HUNAN OF CHINA AND ITS PALAEOECOLOGICAL SIGNIFICANCE

作　　者：吕丹[1] 马学平[1] LU Dan MA Xue-ping(Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences,Peking University ,Beijing 100871 ,China)

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》2017年第2期189-200,共12页Acta Palaeontologica Sinica

基　　金：国家自然科学基金项目(41290260及40872007)资助

摘　　要：基于大量不同生长阶段的标本,本文绘制华南湘中蒋家桥剖面C1-0和佘田桥剖面S-Y-4两个样品共10种小型腕足动物的种群结构和生存曲线,结果显示,C1-0动物群内没有一种腕足类的大小-频率分布呈典型的正常钟型分布模式,仅Thomasaria?baii,Thomasaria?liangi,Xiangia liaoi,Cyrtinaella?houi及Gypidula xui的直方图有些类似钟型分布,而Qidongia tani,Athyris supervittata及Levipugnax?liui的直方图则呈明显的右斜型***分布。各种群生存曲线表现为不同程度的下凹型,这可能与它们生活在泥质软基底的环境有关。Thomasaria?baii为浅凹型,Levipugnax?liui,Xiangia liaoi,Gypidula xui,Qidongia tani及Cyrtinaella?houi为中凹型,Athyris supervittata及Thomasaria?liangi呈深凹型;依次反映的是更高的幼年期死亡率,之后死亡率持续降低的特点,而上述大小-频率分布和生存曲线型式的差异则可能反映了不同种类对环境条件适应程度的差异,例如不同的壳形可能导致的应对软基底及取食效率的区别。对蒋家桥剖面Iowatrypapseudobodini和佘田桥剖面Hunanotoechia tieni块体采样及手捡采样两种不同方法的结果对比表明,采样方法可以不同程度地影响腕足动物种群的大小-频率分布及生存曲线。为了获得最接近真实情况的生存曲线,工作中应尽量采用两种方法相结合。Survivorship curves and distributions of 10 fossil species been depicted based on abun brachiopod specimens of various two samples （C1-0 of Jiangjiaqi Shetianqiao sections） from Hu souther butions n China. None of the C1-0 f of aun size-frequency populations have dant small-sized growth stages of ao and S-Y-4 of nan Province of the size-frequency distria are of a normal bell-shaped distribution pattern; only those of Thomasaria ？ baii, Thomasaria？ liangi, Xiangia liaoi , Cyrtinaella？ houi and resemble a bell-shaped Gypidula xui somewhat distribution, whereas Qidongia tani, Athyris supervittata and Levipugnax？ liui display a distinct right-skewed pattern. The survivorship curves of various populations are of the concave type of various probably related with their substrate. Survivorship curv is slightly concave, whereas degrees, which was living on the muddy e of Thomasaria？ baii those of other species are of either moderately concave type, e. g., Levipugnax？ liui, Xiangia liaoi, Gypidula xui, Qidongia tani and Cyrtinaella？ houi, or strongly concave type, e. g., Athyris supervittata and Thomasaria？ liangi, suggesting a high mortality rate during the juvenile stage and decreasing mortality rate towards the gerontic stage. The above differences in size-frequency distributions and survivorship curves of various species are probably a result of their adaptational differences to the muddy environments. For example, diffe- rences in shell shape might be related with their adaptational differences to both muddy substrate and feeding efficiency. Study of Iowatrypa pseudobodini and Hunanotoechia tieni shows that size-frequency distributions and survivorship curves of brachiopod populations can be affected by sampling methods to various degrees in case of fewer specimens by hand-picking. Bulk sampling is recommended for population analysis, in combination with hand-picking in some cases for more actual survivorship curves.

关 键 词：小型腕足动物 种群结构 生存曲线 块体采样 泥盆纪 

分 类 号：Q915[天文地球—古生物学与地层学]