New information on Brindabellaspis stensioi Young, 1980, highlights morphological disparity in Early Devonian placoderms

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Date
2018-04-26
Authors
King, Benedict
Young, Gavin C
Long, John A
Journal Title
Journal ISSN
Volume Title
Publisher
The Royal Society Publishing
Rights
© 2018 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.
Rights Holder
© 2018 The Authors.
Abstract
Acid-prepared specimens of the placoderm Brindabellaspis stensioi (Early Devonian of New South Wales, Australia) revealed placoderm endocranial anatomy in unprecedented detail. Brindabellaspis has become a key taxon in discussions of early gnathostome phylogeny, and the question of placoderm monophyly versus paraphyly. The anterior orientation of the facial nerve and related hyoid arch structures in this taxon resemble fossil osteostracans (jawless vertebrates) rather than other early gnathostomes. New specimens of Brindabellaspis now reveal the previously unknown anterior region of the skull, including an exceptionally elongate premedian bone forming a long rostrum, supported by a thin extension of the postethmo-occipital unit of the braincase. Lateral overlap surfaces indicate an unusual anterior position for the jaws. Digital rendering of a synchrotron radiation scan reveals a uniquely specialized ethmoid commissure sensory canal, doubled back and fused into a midline canal. The visceral surface of the premedian bone has a plexus of perichondral bone canals. An updated skull roof reconstruction of Brindabellaspis adds to the highly variable dermal skull patterns of the probably non-monophyletic ‘acanthothoracids’. The unusual morphology revealed by the new specimens suggests that the earliest known reef fish fauna contained a diverse range of fishes with specialized ecological roles.
Description
Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.
Keywords
placoderms, Devonian, lateral line
Citation
King, B., Young, G.C., Long, J.A., (2018). New information on Brindabellaspis stensioi Young, 1980, highlights morphological disparity in Early Devonian placoderms. R. Soc. open sci. 5: 180094.