DISCOVERY OF<em>EOPETALOCRINUS</em>(gen.nov.)IN LOWER ORDOVICIAN DAWAN FORMATION AT LIUJIACHANG, SONGZI, HUBEI AND ITS SIGNIFICANCE

Li Luozhao

doi:10.11743/ogg19930402

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DISCOVERY OFEOPETALOCRINUS(gen.nov.)IN LOWER ORDOVICIAN DAWAN FORMATION AT LIUJIACHANG, SONGZI, HUBEI AND ITS SIGNIFICANCE
Vol. 14, Issue 4, Pages: 272-277(1993)
Online First：25 December 1993，

Published：1993
DOI： 10.11743/ogg19930402
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DOI：

Li Luozhao. DISCOVERY OFEOPETALOCRINUS(gen.nov.)IN LOWER ORDOVICIAN DAWAN FORMATION AT LIUJIACHANG, SONGZI, HUBEI AND ITS SIGNIFICANCE[J]. 1993, 14(4): 272-277. DOI: 10.11743/ogg19930402. DOI：

摘要

本文描述了产自湖北松滋刘家场下奥陶统大湾组的花瓣海百科的一个新属——Eopetalocrinus(gen.nov.)

新属的发现对探索花瓣海百合类的起源和演化将具有十分重要的意义。文中对花瓣海百合类腕扇的活动方式及其演变进行了讨论

并对花瓣海百合科现有的几个属的演化关系提出了一些设想。

Abstract

The materials treated in this paper were collected from the Lower Ordovician Dawan Formation of Liujiachang

Songzi County

Hubei Province by Dr.Liu Binli in 1991.Two specimens have been identified to be a new genus—Eopetalocrinus(gen.nov.)from the arm structure

and it is placed provisinally Family Petalocrinidae.This discovery is con-siderably important in studying the genesis and the evolution of Petalocrinidae.The arms differ from those genera's

which belong to petalocrinidae in lateral conjunction.All members of the Family Petalocrinidae were discovered from the Silurian

except for the new genus which exists in the Early Ordovician.Perhaps the present new genus is an an-cestry from the arm structure.The evolutional relationship among all genera of the Petalocrinidae may be shown as follows:Eopetalocrinus(gen.nov.)→Petalocrinus→Sinopetalocrinus→Spirocrinus.Description of new genusEopetalocrinus(gen.nov.)Description There are five arm-fans

which are connected with each other like a flower with five petals fully expanded.Outline is almost rhombic due to the regeneration of about 40 mm long and 26 mm wide

but it is a subcircular in the original shape.The arm-fan has an 75°angle with 18—28 grooves on the ventral surface except a smallarm-fan

which has an angle only about 50°with 6 grooves.The grooves are proved bythe mode of branching with Ⅱ-Ⅳ times.The dorsal surface is smooth.The articualr facets are about fusiform in shape

their insides formed a pentagon about 5 mm in diameter. Type species Eopetalocrinus sinensis(gen.et sp.nov.)Distribution and Age Early Ordovician

Hubei

China.