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Testing the patterning cascade model of cusp development in Macaca fascicularis mandibular molars

Chapple, Simon A., Smith, Tanya M., Skinner, Matthew M. (2024) Testing the patterning cascade model of cusp development in Macaca fascicularis mandibular molars. Archives of Oral Biology, 167 . Article Number 106067. ISSN 0003-9969. (doi:10.1016/j.archoralbio.2024.106067) (KAR id:106845)

Abstract

Objective

Molar crown configuration plays an important role in systematics, and functional and comparative morphology. In particular, the number of cusps on primate molars is often used to identify fossil species and infer their phylogenetic relationships. However, this variability deserves renewed consideration as a number of studies now highlight important developmental mechanisms that may be responsible for the presence of molar cusps in some mammalian taxa. Experimental studies of rodent molars suggest that cusps form under a morphodynamic, patterning cascade model of development (PCM) that involve the iterative formation of enamel knots. This model posits that the size, shape and location of the first-forming cusps determines the presence and positioning of later-forming cusps.

Design

Here we test whether variation in accessory cusp presence in 13 Macaca fascicularis mandibular second molars (M2s) is consistent with predictions of the PCM. Using micro-CT, we imaged these M2s and employed geometric morphometrics to examine whether shape variation in the enamel-dentine junction (EDJ) correlates with accessory cusp presence.

Results

We find that accessory cusp patterning in macaque M2s is broadly consistent with the PCM. Molars with accessory cusps were larger in size and possessed shorter relative cusp heights compared to molars without accessory cusps. Peripheral cusp formation was also associated with more centrally positioned primary cusps, as predicted by the PCM.

Conclusions

While these results demonstrate that a patterning cascade model is broadly appropriate for interpreting cusp variation in Macaca fascicularis molars, it does not explain all manifestations of accessory cusp expression in this sample.

Item Type: Article
DOI/Identification number: 10.1016/j.archoralbio.2024.106067
Uncontrolled keywords: tooth; accessory cusp; cusp nomenclature; iterative development; odontogenesis; Macaca
Subjects: G Geography. Anthropology. Recreation > GN Anthropology
Q Science > QH Natural history > QH75 Conservation (Biology)
Divisions: Divisions > Division of Human and Social Sciences > School of Anthropology and Conservation
Funders: European Research Council (https://ror.org/0472cxd90)
National Science Foundation (https://ror.org/021nxhr62)
SWORD Depositor: JISC Publications Router
Depositing User: JISC Publications Router
Date Deposited: 13 Aug 2024 13:54 UTC
Last Modified: 19 Aug 2024 11:53 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/106845 (The current URI for this page, for reference purposes)

University of Kent Author Information

Chapple, Simon A..

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