The role of the water voles (Arvicola, Rodentia) in the Quatemary

Abstract

Arvicolids are rodents which have molars with a morphology formed by a sequence of enamel folds similar to the curve y = sin f(x). The morphology of the crown of the first lower molar (mi) of living species of Arvicola (large voles) is identified with six criteria, irrespective of tooth size. When rootless arvicolid fossil communities are analysed, it can be seen that the mi morphology of Arvicola is present in those communities represented by specimens of small size at the beginning of the Quaternary. Before this data was known, the presence of Arvicola communities could only be detected in the second half of the Quaternary, when the specimens were comparable to the large size characterising living species. The existence of communities of small-sized Arvicola at the beginning of the Quaternary implies that the mi of Arvicola undergoes a continuous and accelerated growth throughout the entire Quatemary, which allows representatives the genus to be used as a chronological tool. These data mean that it is necessary to change the concept of the genus Allophaiomys and to formulate a new classification to reflect evolutionary relationships of quatemary arvicolids.