Specialized appendages in fuxianhuiids and the head organization of early euarthropods

Yang, Jie and Ortega-Hernández, Javier and Butterfield, Nicholas J. and Zhang, Xi-guang (2013) Specialized appendages in fuxianhuiids and the head organization of early euarthropods. Nature, 494 (7438). pp. 468-471. ISSN 0028-0836 DOI https://doi.org/10.1038/nature11874

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Official URL: http://www.nature.com/nature/journal/v494/n7438/fu...


The organization of the head provides critical data for resolving the phylogenetic relationships and evolutionary history of extinct and extant euarthropods. The early Cambrian-period fuxianhuiids are regarded as basal representatives of stem-group Euarthropoda, and their anterior morphology therefore offers key insights for reconstructing the ancestral condition of the euarthropod head. However, the paired post-antennal structures in Fuxianhuia protensa remain controversial; they have been interpreted as both /`great appendages/' and as gut diverticulae. Here we describe Chengjiangocaris kunmingensis sp. nov. and Fuxianhuia xiaoshibaensis sp. nov. from a new early Cambrian (Stage 3) fossil Lagerstatte in Yunnan, China. Numerous specimens of both species show a unique /`taphonomic dissection/' of the anterodorsal head shield, revealing the cephalic organization in detail. We demonstrate the presence of a pair of specialized post-antennal appendages (SPAs) in the fuxianhuiid head, which attach at either side of the posteriorly directed mouth, behind the hypostome. Preserved functional articulations indicate a well-defined but restricted range of limb movement, suggestive of a simple type of sweep feeding. The organization of the SPAs in fuxianhuiids is incompatible with the (deutocerebral) anterior raptorial appendages of megacheirans, and argue against the presence of protocerebral limbs in the fuxianhuiids. The positions of the fuxianhuiid antennae and SPAs indicate that they are segmentally homologous to the deutocerebral and tritocerebral appendages of crown-group Euarthropoda respectively. These findings indicate that antenniform deutocerebral appendages with many podomeres are a plesiomorphic feature of the ancestral euarthropod head.

Item Type: Article
Uncontrolled Keywords: 2013AREP; IA65;
Subjects: 04 - Palaeobiology
Divisions: 04 - Palaeobiology
Journal or Publication Title: Nature
Volume: 494
Page Range: pp. 468-471
Identification Number: https://doi.org/10.1038/nature11874
Depositing User: Sarah Humbert
Date Deposited: 09 Mar 2013 12:50
Last Modified: 23 Jul 2013 10:05
URI: http://eprints.esc.cam.ac.uk/id/eprint/2688

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