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Romundina and the evolutionary origin of teeth

Theories on the origin of vertebrate teeth have long focused on chondrichthyans as reflecting a primitive condition—but this is better informed by the extinct placoderms, which constitute a sister clade or grade to the living gnathostomes. Here, we show that ‘supragnathal’ toothplates from the acant...

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Autores principales: Rücklin, Martin, Donoghue, Philip C. J.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4528481/
https://www.ncbi.nlm.nih.gov/pubmed/26109615
http://dx.doi.org/10.1098/rsbl.2015.0326
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author Rücklin, Martin
Donoghue, Philip C. J.
author_facet Rücklin, Martin
Donoghue, Philip C. J.
author_sort Rücklin, Martin
collection PubMed
description Theories on the origin of vertebrate teeth have long focused on chondrichthyans as reflecting a primitive condition—but this is better informed by the extinct placoderms, which constitute a sister clade or grade to the living gnathostomes. Here, we show that ‘supragnathal’ toothplates from the acanthothoracid placoderm Romundina stellina comprise multi-cuspid teeth, each composed of an enameloid cap and core of dentine. These were added sequentially, approximately circumferentially, about a pioneer tooth. Teeth are bound to a bony plate that grew with the addition of marginal teeth. Homologous toothplates in arthrodire placoderms exhibit a more ordered arrangement of teeth that lack enameloid, but their organization into a gnathal, bound by layers of cellular bone associated with the addition of each successional tooth, is the same. The presence of enameloid in the teeth of Romundina suggests that it has been lost in other placoderms. Its covariation in the teeth and dermal skeleton of placoderms suggests a lack of independence early in the evolution of jawed vertebrates. It also appears that the dentition—manifest as discrete gnathal ossifications—was developmentally discrete from the jaws during this formative episode of vertebrate evolution.
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spelling pubmed-45284812015-08-11 Romundina and the evolutionary origin of teeth Rücklin, Martin Donoghue, Philip C. J. Biol Lett Palaeontology Theories on the origin of vertebrate teeth have long focused on chondrichthyans as reflecting a primitive condition—but this is better informed by the extinct placoderms, which constitute a sister clade or grade to the living gnathostomes. Here, we show that ‘supragnathal’ toothplates from the acanthothoracid placoderm Romundina stellina comprise multi-cuspid teeth, each composed of an enameloid cap and core of dentine. These were added sequentially, approximately circumferentially, about a pioneer tooth. Teeth are bound to a bony plate that grew with the addition of marginal teeth. Homologous toothplates in arthrodire placoderms exhibit a more ordered arrangement of teeth that lack enameloid, but their organization into a gnathal, bound by layers of cellular bone associated with the addition of each successional tooth, is the same. The presence of enameloid in the teeth of Romundina suggests that it has been lost in other placoderms. Its covariation in the teeth and dermal skeleton of placoderms suggests a lack of independence early in the evolution of jawed vertebrates. It also appears that the dentition—manifest as discrete gnathal ossifications—was developmentally discrete from the jaws during this formative episode of vertebrate evolution. The Royal Society 2015-06 /pmc/articles/PMC4528481/ /pubmed/26109615 http://dx.doi.org/10.1098/rsbl.2015.0326 Text en http://creativecommons.org/licenses/by/4.0/ © 2015 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.
spellingShingle Palaeontology
Rücklin, Martin
Donoghue, Philip C. J.
Romundina and the evolutionary origin of teeth
title Romundina and the evolutionary origin of teeth
title_full Romundina and the evolutionary origin of teeth
title_fullStr Romundina and the evolutionary origin of teeth
title_full_unstemmed Romundina and the evolutionary origin of teeth
title_short Romundina and the evolutionary origin of teeth
title_sort romundina and the evolutionary origin of teeth
topic Palaeontology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4528481/
https://www.ncbi.nlm.nih.gov/pubmed/26109615
http://dx.doi.org/10.1098/rsbl.2015.0326
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