Are there two distinct types of hypocone in Eocene primates? The “pseudohypocone” of notharctines revisited
- UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
- Robert Anemone, Professor and Department Head (Creator)
- Institution
- The University of North Carolina at Greensboro (UNCG )
- Web Site: http://library.uncg.edu/
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.
Are there two distinct types of hypocone in Eocene primates? The “pseudohypocone” of notharctines revisited
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Created on 11/13/2013
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Additional Information
- Publication
- Palaeontologia Electronica, 15.3.26A
- Language: English
- Date: 2012
- Keywords
- upper molars, history, modern humans, extant primates, therian mamals, eocene primates, hypocone, anthropology