Rhagamys

Rhagamys is an extinct genus of rodents in the subfamily Murinae, the Old World mice and rats. The genus was established by the Swiss zoologist Charles Immanuel Forsyth Major to accommodate Rhagamys orthodon, commonly known as Hensel's field mouse or the Tyrrhenian field rat, which is the only species in the genus. It was endemic to the Mediterranean islands of Corsica and Sardinia, where it first appeared in the fossil record in the Late Pleistocene, and was relatively large in size, weighing up to 50 g.[1] Its closest living relatives are of the genus Apodemus.

Rhagamys
Temporal range:
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Muridae
Tribe: Apodemini
Genus: †Rhagamys
Major, 1905
Species:
†R. orthodon
Binomial name
†Rhagamys orthodon
Hensel, 1856

Taxonomy and evolution

The ancestors of Rhagamys, belonging the widespread genus Rhagapodemus, first arrived in Corsica-Sardinia during the Early-Late Pliocene transition, around 3.6 million years ago. Three chronospecies of the lineage have been named, including "Rhagapodemus" azzarolii from the earliest Late Pliocene, followed by "Rhagapodemus" minor from the Early Pleistocene, succeeded by Rhagamys orthodon, which ranged from the Middle Pleistocene to Holocene.[2] The molars of Rhagamys are similar to those of the wood mouse (Apodemus sylvaticus) and the striped field mouse (Apodemus agrarius) but are larger and more derived, being hypsodont teeth suitable for feeding on a coarse, abrasive diet.[1] Over time, Rhagamys orthodon increased in size and became larger than the broad-toothed field mouse (Apodemus mystacinus).[3]

History

Before the arrival of humans on the islands in about 8000 BC, Corsica and Sardinia had their own highly endemic depauperate terrestrial mammal fauna which besides Rhagamys orthodon included a species of dwarf mammoth (Mammuthus lamarmorai), the Tyrrhenian vole (Microtus henseli), the Sardinian pika (Prolagus sardus), one or two species of shrew belonging to the genus Asoriculus, a mole (Talpa tyrrhenica), the Sardinian dhole (Cynotherium sardous), a galictine mustelid (Enhydrictis galictoides), three species of otter (Algarolutra majori, Sardolutra ichnusae, Megalenhydris barbaricina) and a deer (Praemegaceros cazioti). The small mammals, including Rhagamys, persisted for many thousands of years after the first human arrival on the islands, with the youngest radiocarbon dates for Rhagamys dating to around 800 BC. It was almost certainly extinct by the 6th century AD. The cause of the extinction is unknown, but may be due to invasive species introduced by new arrivals to the islands such as Carthaginians and the Romans.[4]

The only endemic mammal still found on the islands is the Sardinian long-eared bat (Plecotus sardus).[5][6]

References
  1. Musser, G.G.; Carleton, M.D. (2005). "Superfamily Muroidea". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 1496–1497. ISBN 978-0-8018-8221-0. OCLC 62265494.
  2. Piras, Paolo; Sansalone, Gabriele; Marcolini, Federica; Tuveri, Caterinella; Arca, Marisa; Kotsakis, Tassos (2012-11-30). "Evolutionary Trends and Stasis in Molar Morphology of Rhagapodemus-Rhagamys Lineage in the Pleistocene of Sardinia". Rivista italiana di Paleontologia e Stratigrafia. 118 (3). doi:10.13130/2039-4942/6018.
  3. Alexandra van der Geer; George Lyras; John de Vos; Michael Dermitzakis (2011). Evolution of Island Mammals: Adaptation and Extinction of Placental Mammals on Islands. John Wiley & Sons. p. 124. ISBN 978-1-4443-9128-2.
  4. Valenzuela, Alejandro; Torres-Roig, Enric; Zoboli, Daniel; Pillola, Gian Luigi; Alcover, Josep Antoni (2021-11-29). "Asynchronous ecological upheavals on the Western Mediterranean islands: New insights on the extinction of their autochthonous small mammals". The Holocene. 32 (3): 137–146. doi:10.1177/09596836211060491. ISSN 0959-6836.
  5. Mucceda, M.; Kiefer, A.; Pidincedda, E.; Veith, M. (2002). "A new species of long-eared bat (Chiroptera, Vespertilionidae) from Sardinia (Italy)" (PDF). Acta Chiropterologica. 4 (2): 121–135. doi:10.3161/001.004.0202.
  6. Amori,Giovanni; Gippoliti, Spartaco; Luiselli, Luca (2013). "A short review of the roles of climate and man in mammal extinctions during the Anthropocene". Anthropocene—Natural and Man-made Alterations of the Earth's Fragile Equilibrium. 25: 95–99. doi:10.1007/s12210-013-0240-6. S2CID 84651348.
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