Tooth-Like Scales in Early Devonian Eugnathostomes and the ‘Outside-In’ Hypothesis for the Origins of Teeth in Vertebrates
Although teeth are considered one of the most important steps in vertebrate evolution, details of their origins are obscure. Two prominent and opposing theories for the evolution of the vertebrate dentition are current: the ‘Outside-in’ hypothesis and the ‘inside-out’ hypothesis. One of the main arg...
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ftbioone:10.1080/039.031.0611 2024-06-02T08:10:14+00:00 Tooth-Like Scales in Early Devonian Eugnathostomes and the ‘Outside-In’ Hypothesis for the Origins of Teeth in Vertebrates Stephanie A. Blais Lindsay A. MacKenzie Mark V. H. Wilson Stephanie A. Blais Lindsay A. MacKenzie Mark V. H. Wilson world 2011-11-01 text/HTML https://doi.org/10.1080/039.031.0611 en eng The Society of Vertebrate Paleontology doi:10.1080/039.031.0611 All rights reserved. https://doi.org/10.1080/039.031.0611 Text 2011 ftbioone https://doi.org/10.1080/039.031.0611 2024-05-07T00:51:19Z Although teeth are considered one of the most important steps in vertebrate evolution, details of their origins are obscure. Two prominent and opposing theories for the evolution of the vertebrate dentition are current: the ‘Outside-in’ hypothesis and the ‘inside-out’ hypothesis. One of the main arguments against the ‘outside-in’ hypothesis is that, although similarities between teeth and scales have been observed, there is little fossil evidence of transitional forms between the two structures. Specimens of ischnacanthid acanthodians from the Man On The Hill (MOTH) locality in the Mackenzie Mountains of Canada provide the first unequivocal example of such transitional forms in an Early Devonian (Lochkovian) vertebrate assemblage. The head scales of these specimens are modified with proximity to the mouth to be extremely tooth-like. Three distinct morphotypes of modified cheek and lip scales are described. Their detailed similarity to teeth suggests that they are a result of the same developmental processes, and also suggests the existence of a field of gene expression near the mouth margin in which scales could be transformed into teeth. These transitional forms remove one of the chief objections to the ‘outside-in’ hypothesis for the origins of teeth in vertebrates. Text Mackenzie mountains BioOne Online Journals Canada |
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ftbioone |
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English |
description |
Although teeth are considered one of the most important steps in vertebrate evolution, details of their origins are obscure. Two prominent and opposing theories for the evolution of the vertebrate dentition are current: the ‘Outside-in’ hypothesis and the ‘inside-out’ hypothesis. One of the main arguments against the ‘outside-in’ hypothesis is that, although similarities between teeth and scales have been observed, there is little fossil evidence of transitional forms between the two structures. Specimens of ischnacanthid acanthodians from the Man On The Hill (MOTH) locality in the Mackenzie Mountains of Canada provide the first unequivocal example of such transitional forms in an Early Devonian (Lochkovian) vertebrate assemblage. The head scales of these specimens are modified with proximity to the mouth to be extremely tooth-like. Three distinct morphotypes of modified cheek and lip scales are described. Their detailed similarity to teeth suggests that they are a result of the same developmental processes, and also suggests the existence of a field of gene expression near the mouth margin in which scales could be transformed into teeth. These transitional forms remove one of the chief objections to the ‘outside-in’ hypothesis for the origins of teeth in vertebrates. |
author2 |
Stephanie A. Blais Lindsay A. MacKenzie Mark V. H. Wilson |
format |
Text |
author |
Stephanie A. Blais Lindsay A. MacKenzie Mark V. H. Wilson |
spellingShingle |
Stephanie A. Blais Lindsay A. MacKenzie Mark V. H. Wilson Tooth-Like Scales in Early Devonian Eugnathostomes and the ‘Outside-In’ Hypothesis for the Origins of Teeth in Vertebrates |
author_facet |
Stephanie A. Blais Lindsay A. MacKenzie Mark V. H. Wilson |
author_sort |
Stephanie A. Blais |
title |
Tooth-Like Scales in Early Devonian Eugnathostomes and the ‘Outside-In’ Hypothesis for the Origins of Teeth in Vertebrates |
title_short |
Tooth-Like Scales in Early Devonian Eugnathostomes and the ‘Outside-In’ Hypothesis for the Origins of Teeth in Vertebrates |
title_full |
Tooth-Like Scales in Early Devonian Eugnathostomes and the ‘Outside-In’ Hypothesis for the Origins of Teeth in Vertebrates |
title_fullStr |
Tooth-Like Scales in Early Devonian Eugnathostomes and the ‘Outside-In’ Hypothesis for the Origins of Teeth in Vertebrates |
title_full_unstemmed |
Tooth-Like Scales in Early Devonian Eugnathostomes and the ‘Outside-In’ Hypothesis for the Origins of Teeth in Vertebrates |
title_sort |
tooth-like scales in early devonian eugnathostomes and the ‘outside-in’ hypothesis for the origins of teeth in vertebrates |
publisher |
The Society of Vertebrate Paleontology |
publishDate |
2011 |
url |
https://doi.org/10.1080/039.031.0611 |
op_coverage |
world |
geographic |
Canada |
geographic_facet |
Canada |
genre |
Mackenzie mountains |
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Mackenzie mountains |
op_source |
https://doi.org/10.1080/039.031.0611 |
op_relation |
doi:10.1080/039.031.0611 |
op_rights |
All rights reserved. |
op_doi |
https://doi.org/10.1080/039.031.0611 |
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