The type material and the enamel structure of Villanyia exilis KRETZOI, 1956 (Arvicolidae, Rodentia)

Abstract. Re-examination of the two teeth constituting the original type and genotype material of Villanyia exilis KRETZOI, 1956 from Villany-5, Hungary, indicates that subsequently published descriptions need revision. The tooth selected as the lectotype of Villanyia exilis by RABEDER (1981) is considered here to belong to Clethrionomys kretzoii (KOWALSKI, 1958). The second specimen, with morphology in accordance with the original description of Kretzoi, is considered to represent the characters of Villanyia exilis. In order to stabilise the nomenclature in accordance with current usage an application has been made to the International Commission on Zoological Nomenclature. The fine structure of the enamel of Villanyia exilis as defined above is described for the first time, based on a tooth from the Late Villanyian of Osztramos-3, Hungary. It demonstrates a simple grade of arvicolid evolution. This enamel type differs substantially from the enamel structure of material from Rebielice Krolewskie, Poland, which was originally identified asMimomys (Villanyia) exilis by KOWALSKI (1960), but considered here to be referable to the genus Borsodia. The generic name Villanyia has been applied widely in the literature to various other taxa, mainly species of extinct rooted lagurine voles which are currently referred to the genus Borsodia (JANOSSY & VAN DERMEULEN, 1975). It is proposed to limit the use of the genus name Villanyia to the latest part of a lineage of uncertain origin which became extinct close to the Villanyian/Biharian boundary.