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Vaškaninová V, Chen D, Tafforeau P, Johanson Z, Ekrt B, Blom H, Ahlberg PE. Marginal dentition and multiple dermal jawbones as the ancestral condition of jawed vertebrates. Science 2020; 369:211-216. [PMID: 32647004 DOI: 10.1126/science.aaz9431] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 05/18/2020] [Indexed: 11/02/2022]
Abstract
The dentitions of extant fishes and land vertebrates vary in both pattern and type of tooth replacement. It has been argued that the common ancestral condition likely resembles the nonmarginal, radially arranged tooth files of arthrodires, an early group of armoured fishes. We used synchrotron microtomography to describe the fossil dentitions of so-called acanthothoracids, the most phylogenetically basal jawed vertebrates with teeth, belonging to the genera Radotina, Kosoraspis, and Tlamaspis (from the Early Devonian of the Czech Republic). Their dentitions differ fundamentally from those of arthrodires; they are marginal, carried by a cheekbone or a series of short dermal bones along the jaw edges, and teeth are added lingually as is the case in many chondrichthyans (cartilaginous fishes) and osteichthyans (bony fishes and tetrapods). We propose these characteristics as ancestral for all jawed vertebrates.
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Affiliation(s)
- Valéria Vaškaninová
- Department of Organismal Biology, Uppsala University, Norbyvägen 18A, SE-752 36, Uppsala, Sweden. .,Institute of Geology and Palaeontology, Faculty of Science, Charles University, Albertov 6, Prague, 12843, Czech Republic
| | - Donglei Chen
- Department of Organismal Biology, Uppsala University, Norbyvägen 18A, SE-752 36, Uppsala, Sweden
| | - Paul Tafforeau
- European Synchrotron Radiation Facility, 71 avenue des Martyrs, 38043 Grenoble, France
| | - Zerina Johanson
- Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - Boris Ekrt
- Department of Palaeontology, National Museum, Václavské náměstí 68, Prague, 11579, Czech Republic
| | - Henning Blom
- Department of Organismal Biology, Uppsala University, Norbyvägen 18A, SE-752 36, Uppsala, Sweden
| | - Per Erik Ahlberg
- Department of Organismal Biology, Uppsala University, Norbyvägen 18A, SE-752 36, Uppsala, Sweden.
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King B, Young GC, Long JA. New information on Brindabellaspis stensioi Young, 1980, highlights morphological disparity in Early Devonian placoderms. ROYAL SOCIETY OPEN SCIENCE 2018; 5:180094. [PMID: 30110452 PMCID: PMC6030278 DOI: 10.1098/rsos.180094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 04/26/2018] [Indexed: 06/08/2023]
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.
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Affiliation(s)
- Benedict King
- College of Science and Engineering, Flinders University, PO Box 2100, Adelaide, South Australia 5001, Australia
- Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, The Netherlands
| | - Gavin C. Young
- Research School of Physics and Engineering (RSPE), Australian National University, Canberra 0200, Australian Capital Territory, Australia
- Australian Museum Research Institute, 1 Williams Street, Sydney New South Wales 2010, Australia
| | - John A. Long
- College of Science and Engineering, Flinders University, PO Box 2100, Adelaide, South Australia 5001, Australia
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