Tooth-like scales in Early Devonian eugnathostomes and the ‘outside-in’ hypothesis for the origins of teeth in vertebrates

Blais, Sylvain; MacKenzie, Lindsay Ann; Wilson, Mark V. H.

doi:10.1080/02724634.2011.607992

Cited by 36 publications

(53 citation statements)

References 37 publications

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“…Furthermore, a gradual transition from facial scales to teeth is present in some articulated ischnacanthid acanthodians [45], suggesting that a dental lamina emerged late in ontogeny in these forms. The patterning relationships indicated by the partly denticulated tooth whorls from Ohessaare may thus be representative for a wide range of acanthodians.…”

Section: Discussionmentioning

confidence: 99%

Scales and Tooth Whorls of Ancient Fishes Challenge Distinction between External and Oral ‘Teeth’

Sanchez

Blom

et al. 2013

PLoS ONE

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The debate about the origin of the vertebrate dentition has been given fresh fuel by new fossil discoveries and developmental studies of extant animals. Odontodes (teeth or tooth-like structures) can be found in two distinct regions, the ‘internal’ oropharyngeal cavity and the ‘external’ skin. A recent hypothesis argues that regularly patterned odontodes is a specific oropharyngeal feature, whereas odontodes in the external skeleton lack this organization. However, this argument relies on the skeletal system of modern chondrichthyans (sharks and their relatives), which differ from other gnathostome (jawed vertebrate) groups in not having dermal bones associated with the odontodes. Their external skeleton is also composed of monoodontode 'placoid scales', whereas the scales of most early fossil gnathostomes are polyodontode, i.e. constructed from several odontodes on a shared bony base. Propagation phase contrast X-ray Synchrotron microtomography (PPC-SRµCT) is used to study the polyodontode scales of the early bony fish Andreolepis hedei. The odontodes constructing a single scale are reconstructed in 3D, and a linear and regular growth mechanism similar to that in a gnathostome dentition is confirmed, together with a second, gap-filling growth mechanism. Acanthodian tooth whorls are described, which show that ossification of the whorl base preceded and probably patterned the development of the dental lamina, in contrast to the condition in sharks where the dental lamina develops early and patterns the dentition.The new findings reveal, for the first time, how polyodontode scales grow in 3D in an extinct bony fish. They show that dentition-like odontode patterning occurs on scales and that the primary patterning unit of a tooth whorl may be the bony base rather than the odontodes it carries. These results contradict the hypothesis that oropharyngeal and external odontode skeletons are fundamentally separate and suggest that the importance of dermal bone interactions to odontode patterning has been underestimated.

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Section: Discussionmentioning

confidence: 99%

Scales and Tooth Whorls of Ancient Fishes Challenge Distinction between External and Oral ‘Teeth’

Sanchez

Blom

et al. 2013

PLoS ONE

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“…This character could possibly be considered independent of character 39, as symphysial tooth whorls appear to have developed between and not on the jaw cartilages, and extraoral elements indistinguishable from tooth whorls occur in some ischnacanthids (Blais et al, 2011). Tetanopsyrus lacks tooth whorls (Burrow and Young, 2012;Newman et al, 2012;CJB pers.…”

Section: Brachyacanthus Culmacanthus Euthacanthusmentioning

confidence: 99%

The diplacanthid fishes (Acanthodii, Diplacanthiformes, Diplacanthidae) from the Middle Devonian of Scotlan

Burrow

Blaauwen

Newman³

et al. 2016

Palaeontologia Electronica

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“…These are modified from the typical head scale form to one that is slender, needle-like, and asymmetrical, pointing toward the occlusal margin of the jaws. The cheek scales are not well preserved in UALVP 42660, but there are four curved ridges arcing inward toward a convergence point that likely represent the bases of the tooth whorl-like cheek scales as described in Blais et al (2011).…”

Section: Journal Of Vertebrate Paleontology E948546-7mentioning

confidence: 96%

Four new Early Devonian ischnacanthid acanthodians from the Mackenzie Mountains, Northwest Territories, Canada: an early experiment in dental diversity

Blais¹,

Hermus²,

Wilson³

2015

Journal of Vertebrate Paleontology

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The Early Devonian (Lochkovian) Man On The Hill (MOTH) locality in the Northwest Territories has yielded hundreds of exquisitely preserved specimens of over 72 different species of early vertebrates, greatly increasing our understanding of the diversity of this period. In this paper, we describe three new genera comprising four new species of ischnacanthid acanthodian, based on their dentigerous jaw bones and teeth. This taxonomic diversity reflects some of the diversity of dentition found among ischnacanthiform acanthodians at the MOTH locality, in contrast to their highly conservative body forms. This high diversity of related forms suggests an early radiation in jaw and tooth morphology in Early Devonian ischnacanthiform acanthodians in this region. All ischnacanthiform specimens from MOTH were originally assigned to Ischnacanthus gracilis. However, study of the unique jaw and tooth morphology of MOTH ischnacanthiform specimens indicates that it is unlikely that Ischnacanthus was present at the MOTH locality.http://zoobank.org/urn:lsid:zoobank.

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Tooth-like scales in Early Devonian eugnathostomes and the ‘outside-in’ hypothesis for the origins of teeth in vertebrates

Cited by 36 publications

References 37 publications

Scales and Tooth Whorls of Ancient Fishes Challenge Distinction between External and Oral ‘Teeth’

Scales and Tooth Whorls of Ancient Fishes Challenge Distinction between External and Oral ‘Teeth’

The diplacanthid fishes (Acanthodii, Diplacanthiformes, Diplacanthidae) from the Middle Devonian of Scotlan

Four new Early Devonian ischnacanthid acanthodians from the Mackenzie Mountains, Northwest Territories, Canada: an early experiment in dental diversity

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