AN INDEX FOR CONCAVITY OF THE OCCLUSAL SURFACE OF THE CHEEK TEETH AND AN ASSESSMENT OF CONCAVITY IN GLIRIDAE (MAMMALIA, RODENTIA)
Many studies of fossil Gliridae have found that the concavity of the occlusal surface is an important diagnostic character. However, no objective measure of occlusal concavity exists. In this paper a quantitative concavity index is proposed and tested on the glirid dentition. It may be applicable to other taxa, too.
The index is based on the depth of concavity and the radius of a best-fit circle. We drew anterior and posterior profiles of upper and lower M1 and M2 of over 60 species of Gliridae. These diagrams were digitized, after which six parameters were measured on each profile. We then calculated the radius of the circle that best fits each profile. The depth of the concavity divided by the radius of the best fitting circle was found to be a good measure of concavity. This parameter permits us to quantify descriptive terms like "weakly concave," "moderately concave," or "strongly concave."
The oldest Gliridae, from the late Eocene, have moderately to strongly concave molars. During the late Oligocene various groups of Gliridae developed weakly concave or almost flat molars
Matthijs Freudenthal Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Campus Fuentenueva, Granada, Spain; Nationaal Natuurhistorisch Museum, Postbus 9517, 2300 RA Leiden, The Netherlands.
Elvira Martín-Suárez. Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Campus Fuentenueva, Granada, Spain.
KEY WORDS: Gliridae; dental concavity
PE Article Number: 10.2.9A
Copyright: Society of Vertebrate Paleontology August 2007
Submission: 8 January 2007. Acceptance: 9 July 2007