Kurtén Club 7.2.

Dear all,

tomorrow, Julia Schultz will give a talk about

Occlusal surface analysis of dryolestoid molars (Mammalia, Cladotheria).

Abstract:

The “primary trigon” and trigonid of the pretribosphenic dryolestoid molars are arranged in a reversed triangular pattern of trigon and “primary trigonid”, which is shared with the more plesiomorphic symmetrodontans (Spalacotheriida). During the embrasure shearing process the lower molars fit into the embrasures between the upper molars. A buccally oriented guiding groove of the unicuspid talonid of dryolestids is homologous to the hypoflexid structure of the tribosphenic molar. In dryolestids the shearing surface of this hypoflexid structure has mainly shearing function with a crushing component. However, in tribosphenic molars the hypoflexid is more steeply inclined and less involved in occlusal contacts. Striation analysis and virtual simulation of the relative movements of the molars using the newly developed “Occlusal Fingerprint Analysis”-software demonstrate a functional difference of the dryolestid and the tribosphenic hypoflexid. In the dryolestid hypoflexid, shearing is the important function during the chewing cycle, when the paracone slides buccally along the guiding groove. The average angle of the striations related to the occlusal plane is steeper than the inclination of the guiding groove in the hypoflexid. This indicates that the lower molar moves in two phases into occlusion during the chewing cycle: an initial puncture-crushing phase and a subsequent shearing phase before full centric occlusion. A typical tribosphenic grinding phase after centric occlusion does not occur in dryolestids. During the evolution of the talonid basin, the shearing area of the hypoflexid was displaced buccally and rotated in mesial direction. In combination with the formation of the talonid basin a functional shift in the chewing cycle from shearing to grinding occurred and the hypoflexid lost its function as a main shearing area.

Recent publications:

Schultz, J.A. & Martin, T. (2011): Wear pattern and functional morphology of dryolestoid molars (Mammalia, Cladotheria). Paläontologische Zeitschrift 85 (3): 269-285.

Lazzari, V., Schultz, J.A., Tafforeau, P., Martin, T. (2010): Occlusal pattern in paulchoffatiid multituberculates and the evolution of cusp morphology in mammaliamorphs with rodent-like dentitions. Journal of Mammalian Evolution 17: 177-192.

Time & Loc.:
16.00, 7.2.2012, C108 Physicum

Welcome,
Allu