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Article: Unique damage-related, gap-filling tooth replacement in pycnodont fishes

Palaeontology - Vol. 64 Part 2 - Cover Image
Publication: Palaeontology
Volume: 64
Part: 4
Publication Date: July 2021
Page(s): 489 504
Author(s): Sally E. Collins, and Charlie J. Underwood
Addition Information

How to Cite

COLLINS, S.E., UNDERWOOD, C.J. 2021. . Palaeontology, 64, 4, 489-504. DOI: /doi/10.1111/pala.12539

Author Information

  • Sally E. Collins - Department of Earth & Planetary Sciences Birkbeck, University of London Malet Street, London, WC1E 7HX UK
  • Sally E. Collins - Department of Earth Sciences Natural History Museum Cromwell Road, SW7 5BD London UK
  • Charlie J. Underwood - Department of Earth & Planetary Sciences Birkbeck, University of London Malet Street, London, WC1E 7HX UK
  • Charlie J. Underwood - Department of Earth Sciences Natural History Museum Cromwell Road, SW7 5BD London UK

Publication History

  • Issue published online: 09 June 2021
  • Manuscript Accepted: 08 February 2021
  • Manuscript Received: 26 June 2020

Online Version Hosted By

Wiley Online Library
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Abstract

Most jawed vertebrates (gnathostomes) replace their teeth throughout life (polyphyodonty) and there is currently great interest in its molecular and cellular basis, particularly in fish. While much has still to be elucidated, it appears that whichever tooth replacement mechanism is used, only one tooth replaces one predecessor, at any one time. Here we present fossil crushing dentitions of two extinct pycnodont fishes, Pycnodus zeaformis and Pycnodus maliensis. Their surface features and x-ray micro-CT virtual sections show no evidence of one-for-one replacement. Instead, individual large teeth were replaced by multiple small teeth, for which, as far as we could ascertain, there is no known mechanism. This occurred where underlying dentigerous bone was damaged. Small teeth also developed where parts of large teeth had broken off, and in gaps between large teeth created by the geometry of their close alignment in rows. We compared the virtual sections to those of functionally analogous crushing dentitions of three modern fishes. Contrasting greatly to the pycnodonts, each showed an orderly, one-for-one replacement, typical of osteichthyans. We propose that the pycnodont specimens exhibit a gap-filling tooth addition hitherto unseen in gnathostomes, and that the oral epithelium retained an initiatory competence throughout life, with a programming of ‘if a gap exists, fill it’. This would also have facilitated the addition of large teeth in rows, in space provided by ontogenetic growth. We hypothesize that gaps were registered as an absence of pressure at the crushing surface, initiating tooth development, as in the modern cichlid Astatoreochromis alluaudi.

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