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

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. .

KEYWORDS:

• Insular evolution
• menorca’s third stage of fauna
• pleistocene
• chronospecies
• independent phylogenetic lineage

Acknowledgments

This project has been funded by the Agencia Estatal de Investigación (Spanish Government)(project PID2020-117118GB-100) and the Government of Catalonia (2017-SGR-960 and 2017-SGR-859, CERCA Program). The insightful comments of the two reviewers (Dr. Jelle Reumer, Universiteit Utrecht, Koninkrijk der Nederlanden and Dr. Pedro Piñero, Universidad Nacional de la Plata, Buenos Aires, Argentina) have greatly improved the original manuscript. This work is dedicated to the memory of Joan Quintana Bagur (Ciutadella de Menorca, 1940-2021).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Agencia Estatal de Investigación (Spanish Government) [PID2020-117118GB-100].