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.