Dental variation in Hypnomys mahonensis Bate, 1918 (Gliridae, Rodentia, Mammalia) from the newly rediscovered type-locality of Punta Esquitxador 17 (Menorca, Balearic Islands, Western Mediterranean)

Abstract

ABSTRACT Punta Esquitxador 17 is a small coastal site of karstic origin, formed by very hard red silt, rich in remains of small vertebrates. This is the same site from which Dorothea M. A. Bate recovered and described, in 1918, Hypnomys mahonensis. The limited number of specimens of the type series (a left maxilla, a right mandible and an M1) has, historically, limited the adequate knowledge of this species. The recovery of new remains has allowed us to describe the different dental morphotypes and their comparison with other species of the genus. Overall, H. mahonensis has simpler tooth patterns than Hypnomys morpheus, with isolated ridges in upper M1. Moreover, H. mahonensis displays a small transverse ridge connecting the anteroloph and protoloph. This is a derived feature absent in H. morpheus. Two different hypotheses have been put forward to explain the origin of H. mahonensis: 1) is considered the final representative of a phyletic lineage originating in Menorca; 2) H. mahonensis evolved from the arrival to Menorca of a late representative of the existing phylogenetic line in Mallorca (H. morpheus). ThIsstudyalso made possible to confirm the taxonomic validity of this species and its geographical and temporal distribution. .