Early Cambrian arthropods - new insights into arthropod head and structural evolution

The Cambrian Maotianshan-Shale lagerstatten have yielded fossils of a great variety of taxa, particularly arthropods. We report further information on two of these arthropods, Fuxianhuia protensa and Chengjiangocaris longiformis and present a new species, Shankouia zhenghei. Their morphologies shed...

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Bibliographic Details
Published in:Arthropod Structure & Development
Main Authors: Waloszek, D, Chen, JY (ι™ˆε‡θΏœ), Maas, A, Wang, XQ
Format: Report
Language:English
Published: ELSEVIER SCI LTD 2005
Subjects:
Phylogeny
Limbs
Basipod
Endopod
Exopod
Head Shield
North Greenland
Larval Development
Stem-lineage
Tardigrades
Appendages
Crustacean
Position
Bearing
Fauna
Entomology
Greenland
Online Access:http://ir.nigpas.ac.cn/handle/332004/661
https://doi.org/10.1016/j.asd.2005.01.005
Description
Summary:The Cambrian Maotianshan-Shale lagerstatten have yielded fossils of a great variety of taxa, particularly arthropods. We report further information on two of these arthropods, Fuxianhuia protensa and Chengjiangocaris longiformis and present a new species, Shankouia zhenghei. Their morphologies shed new light on the early evolution of Arthropoda, which can be resolved into three major phases. In the first phase, new features such as segmental uniramous limbs were developed. The second phase is characterized by segmental sclerotizations of body and appendages. In this phase, the head included only the segments bearing lateral eyes and antennae. A shield-like structure is recognized as the expanded tergite of the second head segment. This tergite housed a pair of sac-like structures. Formerly interpreted as appendages in Fuxianhuia, they are regarded here as gut diverticula. Behind the head, all tergites free from the shield-like one are tripartite, made of an elevated middle region and pleurotergites. All post-antennal limbs comprise a multi-annulated rod and an exopod flap. The antenna is limb-shaped and was, most likely, the only structure suitable for food gathering. Remarkably, the two head segments are those anterior segments, which are not expressed by Hox genes. The third step is the development of euarthropod characteristics. (c) 2005 Elsevier Ltd. All rights reserved.

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