自然杂志 ›› 2014, Vol. 36 ›› Issue (1): 34-41.

• 专题综述 • 上一篇    下一篇

寒武纪冠轮动物化石研究进展与假体腔动物的实证起源*

张志飞① 张志亮②   

  1. ①教授，②硕士研究生，西北大学地质学系早期生命研究所及大陆动力学国家重点实验室，西安 710069
  • 收稿日期:2013-10-13 修回日期:2013-11-13 出版日期:2014-02-25 发布日期:2014-02-25
  • 基金资助:

    *国家自然科学基金(41072017)，国际基础研究发展规划(2013CB835002)，西北大学大陆动力学国家重点实验室科技部专项和引智计划111工程(P201102007)资助

New fossil records of Cambrian Lophotrochozoans (Spiralian: Entoprocta) and their implication for pseudocoelomate origin

ZHANG Zhi-fei①, ZHANG Zhi-liang②   

  1. ①Professor ②Master Candidate, Early Life Institute & State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China
  • Received:2013-10-13 Revised:2013-11-13 Online:2014-02-25 Published:2014-02-25

PDF

575

摘要： 冠轮动物(Lophotrochozoa，即Spiralia)几乎涵盖了所有的非蜕皮类原口动物，包括许多不同的动物门类。目前主要分为三个支系，即由软体动物、环节动物、纽形动物、腕足动物、帚虫动物和星虫动物门组成的担轮动物(Trochozoa)，由环口动物、内肛动物和苔藓动物门组成的群居虫类(Polyzoa)，以及由许多小的动物门类组成的扁形动物(Platyzoa)。最近，寒武纪大爆发期间冠轮动物的形态和系统学研究取得了很大的进展，但群居动物和扁形动物两大冠轮分支的化石记录几乎仍是空白。最近，西北大学早期生命研究所对新近收集的400多个瘤状杯形虫(Cotyledion tylodes Luo et Hu, 1999)化石进行了重新研究，表明澄江化石库中早期发现的这类疑难类化石可能代表一类具骨骼的干群内肛动物。研究表明这类生物身体呈高足杯形，由杯形萼部和圆柱形的固着柄组成，固着柄的末端具有盘状的吸盘，用以附着在其他生物的外骨骼或身体上。杯体内具有U型的消化道，两端分别洞开于口和肛门，均包围在由一圈可自由伸缩的柔韧触手组成的纤毛环内。然而与现生的假体腔内肛动物相比，瘤状杯形虫个体较大，身体高度可达8～56 mm，身体表面覆盖一层疏松或紧密排列的圆形或椭圆形的骨片。另外，化石观察表明瘤状杯形虫固着柄的中央具有杯体向后延伸的体腔，属于有体腔类动物。因此，现生内肛动物体腔的丧失可能是衍征(apomorphy)，其微型的身体以及解剖和体壁的简化可能是动物小型化作用(miniaturization)的结果，或者是现生内肛动物群居附着生活的适应性演化有关。具骨骼干群内肛动物的发现对理解早期冠轮生物的系统演化和相互关系有重要意义。

关键词: 寒武纪, 澄江化石库, 冠轮动物, 假体腔动物, 真体腔动物

Abstract: Lophotrochozoa (Spiralian), a clade of non-ecdysozoan protostomes, comprises a large number of animal phyla, recently sub-grouped as tree lineages including Trochozoa (Mollusca, Annelida, Brachiopoda, Phoronida), Polyzoa (Cycliophora, Entoprocta and Bryozoa) and many small Platyzoan phyla. Although considerable advance have recently been made in unveiling the Cambrian morphology and phylogeny of several pivotal spiralian animals, the most conspicuous phylogenetic gap in the fossil records is for Platyzoa and Polyzoa. Recently, the problematic animal Cotyledion tylodes from the Chengjiang fanua (ca. 520 Ma old) has been reinterpreted as sclerite-bearing stem group entoproct based on observations of ca. 400 specimens collected by the working group of Early Life Institute, Northwest University, Xi’an of China. The animal’s body is goblet-shaped, with an upper cup-like calyx (cavity) and lower cylindrical stalked ended by a knob-shaped holdfast providing for exoskeletal attachment. The Calyx contains a U-shaped gut with a mouth and anus surrounded by a crown of flexible, retractable tentacles. When compared to living entoproct cousins, Cotyledion is larger in size, measuring between 8 and 56 mm and with a body covered by loosely or tightly-spaced, rounded or elliptical sclerites. In addition, Cotyledion appears to be coelomate, with a coelomic extension of calyx to the centre of stalk.
It is therefore assumed that the loss of a coelom may represent an apomorphic character in living entoprocts, and their extreme body decrease and severe structural simplification of anatomy and body wall could be taken as a result of miniaturization that is a widespread phenomenon in animals, and an adaptation that may be associated with a change to colonial life in living colonial entoprocts. Thus, the description of entoprocts from the Chengjiang biota has important implications for the earliest evolution of Lophotrochozoans.

Key words: Cambrian (Stage 2), Chengjiang Lagerstatte, Lophotrochozoa, pseudocoelomate animal, coelomate animal

法律公告　|　 联系我们　|　 网站地图