Are there two distinct types of hypocone in Eocene primates? The 'pseudohypocone' of notharctines revisited

Anemone, Robert L. and Skinner, Matthew M. and Dirks, Wendy (2012) Are there two distinct types of hypocone in Eocene primates? The 'pseudohypocone' of notharctines revisited. Palaeontologia Electronica, 15 (3;26A). pp. 1-13. ISSN 1935-3952. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Abstract

Upper molars of modern humans and most extant primates have four cusps that have evolved from the original tribosphenic tooth of therian mammals. These include the three cusps of the original trigon (e.g., paracone, metacone, and protocone), and the addition of the distolingual cusp or hypocone. Among Eocene primates of the family Adapidae, a distinction has long been made between a "true" hypocone associated with the lingual cingulum (adapine form) and a "pseudohypocone" associated with the distal margin of the protocone (notharctine form). The developmental processes underlying these two types of distolingual cusp are unknown, and the validity of the distinction is based on phylogenetic utility and homology rather than cusp position, as in other mammalian groups. To address this issue we use micro-computed tomography to reveal the morphology of the hypocone and associated cusps and crests on the enamel-dentine junction (EDJ). The EDJ preserves the initial steps of tooth crown development and can be used to clarify detailed aspects of crown morphology in variably worn or damaged fossil teeth. Our study sample includes both adapine species from Europe and notharctines from North America. We confirm that the pseudohypocone found among notharctines is a true cusp since it forms as a dentine horn during crown development. Our results also confirm that these two forms of hypocone are developmentally distinct and have evolved convergently in these two primate clades. A review of the paleontological literature suggests that, in spite of the fact that homoplasy is rampant among mammalian clades with respect to the development of the hypocone, only among the notharctines do we find an alternative name for this cusp.

Item Type: Article
Uncontrolled keywords: odontogenesis; primates; adapids; crown morphology; dentition; hypocone
Subjects: Q Science
Divisions: Faculties > Social Sciences > School of Anthropology and Conservation > Biological Anthropology
Depositing User: Matthew Skinner
Date Deposited: 15 May 2015 12:23 UTC
Last Modified: 18 May 2015 09:10 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/48471 (The current URI for this page, for reference purposes)
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