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Ordovician opabiniid-like animals and the role of the proboscis in euarthropod head evolution

Published version
Peer-reviewed

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Authors

Wolfe, Joanna M 

Abstract

jats:titleAbstract</jats:title>jats:pA crucial step in the evolution of Euarthropoda (chelicerates, myriapods, pancrustaceans) was the transition between fossil groups that possessed frontal appendages innervated by the first segment of the brain (protocerebrum), and living groups with a protocerebral labrum and paired appendages innervated by the second brain segment (deutocerebrum). Appendage homologies between the groups are controversial. Here we describe two specimens of opabiniid-like euarthropods, each bearing an anterior proboscis (a fused protocerebral appendage), from the Middle Ordovician Castle Bank Biota, Wales, UK. Phylogenetic analyses support a paraphyletic grade of stem-group euarthropods with fused protocerebral appendages and a posterior-facing mouth, as in the iconic Cambrian panarthropodjats:italicOpabinia</jats:italic>. These results suggest that the labrum may have reduced from an already-fused proboscis, rather than a pair of arthropodized appendages. If some shared features between the Castle Bank specimens and radiodonts are considered convergent rather than homologous, phylogenetic analyses retrieve them as opabiniids, substantially extending the geographic and temporal range of Opabiniidae.</jats:p>

Description

Keywords

Article, /631/181/414, /631/181/757, /631/181/2480, /631/114/739, article

Journal Title

Nature Communications

Conference Name

Journal ISSN

2041-1723

Volume Title

Publisher

Springer Science and Business Media LLC
Sponsorship
University of Cambridge (Herchel Smith Postdoctoral Fellowship)
Chinese Academy of Sciences (CAS) (2020VCB0014, 2018VCB0014)
NSF | BIO | Division of Environmental Biology (DEB) (1856679)