The dentition of a new adult Neanderthal individual from Grotte Mandrin, France

Grotte Mandrin is located in the middle Rhône River Valley, in Mediterranean France, and has yielded 11 Pleistocene archeological and paleoanthropological layers (ranging from the oldest layer J to the youngest layer B) dating from Marine Isotope Stage (MIS) 5 to MIS 3. We report here the nearly complete dentition of an adult Neanderthal individual, nicknamed 'Thorin,' associated to the last phase of the Post-Neronian II, in layer B2 (∼44.50-42.25 ka). A previous paleogenetic analysis revealed that Thorin is a male individual and that he shows a deep genetic divergence with other penecontemporaneous Neanderthals from western Europe that possibly occurred ∼105 ka. The 31 teeth of Thorin (including two distomolars) are described and analyzed using microcomputed tomography imaging and are compared with other Neanderthals and modern humans. Based on direct observation and measurements on the fossil remains, and using microtomographic imaging, tooth wear, nonmetric characters, crown dimensions, and dental tissue proportions were investigated, and the shape of the enamel-dentine junction of the M², M₂, and M₃ was analyzed by geometric morphometrics. Our results indicate that Thorin's teeth show dental characteristics typical of MIS 5-3 Neanderthals. It is also the first time that the presence of two distomolars is reported in a Neanderthal individual, a trait that is rare among modern human populations. Combined with the genetic peculiarities of this individual, the results of the present study imply either a process of morphological convergence among the latest Neanderthal groups or an underestimation of the genetic variability of recent Neanderthal groups.