Rhagamys

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Rhagamys
Temporal range: Pleistocene–Holocene
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Rhagamys orthodon lower hemimandibles, Pleistocene of Corsica.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
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

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, which is the only species in the genus. It was endemic to the Mediterranean islands of Corsica and Sardinia, descending from Rhagapodemus , which had colonised the islands around 3.6 million years ago. Its closest living relatives are of the genus Apodemus, which includes the field and wood mice.

Contents

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. [1] 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. [2] Over time, The Rhagapodemus-Rhagamys lineage increased in size, [3] with Rhagamys orthodon having an estimated mass of approximately 90 grams (3.2 oz), [4] two and a half times larger than its mainland ancestor, an example of island gigantism. [5]

Paleoenvironment and extinction

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 ), the shrew Asoriculus similis , 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 ). [6] 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. [7]

The only endemic mammal still found on the islands is the Sardinian long-eared bat (Plecotus sardus). [8] [9]

Related Research Articles

<span class="mw-page-title-main">Sardinian pika</span> Extinct species of mammal

The Sardinian pika is an extinct species of lagomorph that was endemic to the islands of Sardinia, Corsica and neighbouring Mediterranean islands until its extinction likely in Roman times. It was the last surviving member of Prolagus, a genus of lagomorph once widespread throughout Europe during the Miocene and Pliocene epochs, whose closest living relatives are pikas of the genus Ochotona.

<span class="mw-page-title-main">Dwarf elephant</span> Prehistoric elephant species

Dwarf elephants are prehistoric members of the order Proboscidea which, through the process of allopatric speciation on islands, evolved much smaller body sizes in comparison with their immediate ancestors. Dwarf elephants are an example of insular dwarfism, the phenomenon whereby large terrestrial vertebrates that colonize islands evolve dwarf forms, a phenomenon attributed to adaptation to resource-poor environments and lack of predation and competition.

<i>Apodemus</i> Genus of rodents

Apodemus is a genus of Muridae. The name is unrelated to that of the Mus genus, instead being derived from the Greek ἀπό-δημος.

<span class="mw-page-title-main">Sardinian dhole</span> Extinct species of carnivore

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<i>Candiacervus</i> Extinct genus of deer

Candiacervus is an extinct genus of deer native to Pleistocene Crete. Due to a lack of other herbivores, the genus underwent an adaptive radiation, filling niches occupied by other taxa on the mainland. Due to the small size of Crete, some species underwent insular dwarfism, the smallest species, C. ropalophorus, stood about 40 centimetres (16 in) at the shoulders when fully grown, while other species were relatively large and comparable in size to mainland deer species. Some species are noted for their peculiar, elongate club-shaped antlers, though other species have more normal antlers.

<i>Mammuthus lamarmorai</i> Extinct species of mammal

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<i>Palaeoloxodon cypriotes</i> Extinct species of elephant

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<i>Prolagus</i> Extinct genus of mammals

Prolagus is an extinct genus of lagomorph. Over 20 species have been named, and the genus was abundant and widespread in Europe during the Neogene. However, by the end of the Middle Pleistocene, it was confined to a single species, the Sardinian pika, on the Corsica, Sardinia, and surrounding islands, where it survived into historical times. In North Africa and Western Asia, the genus is known from the Miocene and Pliocene. The scientific name may mean "before hares" or "primitive hares". Its taxonomy is disputed, with it either being considered a member of the family Ochotonidae, which includes living pikas, or the only member of the family Prolagidae.

<i>Xenocyon</i> Extinct subgenus of carnivores

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<i>Megalenhydris</i> Extinct genus of giant otter

Megalenhydris barbaricina is an extinct species of giant otter from the Late Pleistocene of Sardinia. It is known from a single partial skeleton, discovered in the Grotta di Ispinigoli near Dorgali, and was described in 1987. It was larger than any living otter, exceeding the size of South American giant otters (Petrolutra), which can reach two meters in length. The species is one of four extinct otter species from Sardinia and Corsica. The others are Algarolutra majori, Lutra castiglionis and Sardolutra ichnusae. It is suggested to have ultimately originated from the much smaller European mainland species "Lutra" simplicidens, which may be more closely related to Lutrogale than to modern Lutra species. The structure of the teeth points to a diet of bottom dwelling fish and crustaceans. A special characteristic of the species is the flattening of the first few caudal vertebrae. This might point to a slightly flattened tail.

<span class="mw-page-title-main">Sardinian long-eared bat</span> Species of bat

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<i>Palaeoloxodon creutzburgi</i> Extinct species of elephant found on Crete

Palaeoloxodon creutzburgi is an extinct species of elephant known from the Middle-Late Pleistocene of Crete. It is a descendant of the large mainland species Palaeoloxodon antiquus. It is known from localities across the island. P. chaniensis from Stylos and in Vamos cave, Chania, west Crete is considered to be a junior synonym of P. creutzburgi. It had undergone insular dwarfism, being approximately 40% of the size of its mainland ancestor, and was around the size of the living Asian elephant. It lived alongside the radiation of Candiacervus deer endemic to the island, the mouse Mus batae-minotaurus, the Cretan otter, and the Cretan shrew.

<i>Talpa tyrrhenica</i> Extinct species of mammal

Talpa tyrrhenica, also known as the Tyrrhenian mole, is an extinct species of mole belonging to the genus Talpa. It was endemic to the Mediterranean islands of Corsica and Sardinia during the Pleistocene epoch.

Microtus (Tyrrhenicola) henseli is an extinct species of vole belonging to the genus Microtus that was endemic to Sardinia and Corsica during the Pleistocene and Holocene.

<span class="mw-page-title-main">Corbeddu Cave</span> Cave and archaeological site in Italy

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Kritimys, also known as the Cretan giant rat is an extinct genus of murid rodent that was endemic to the island of Crete during the Early and Middle Pleistocene. There are two known species, K. kiridus from the Early-Mid Pleistocene, and its descendant K. catreus from the Middle Pleistocene. It is suggested to be closely related to and probably derived from Praomys. As with most island rodents, Kritimys was larger than its mainland relatives, with its size increasing over time, with K. catreus estimated to weigh 518 grams (1.142 lb), around 6.7 times the weight of its mainland ancestor, an example of island gigantism. The temporal range of the genus is considered to define the regional Kritimys biozone, during which time there were only two other species of mammal native to the island, a species of dwarf mammoth, Mammuthus creticus and the dwarf hippopotamus Hippopotamus creutzburgi. It became extinct during the late Middle Pleistocene, following the arrival of the Mus bateae-minotaurus lineage to the island, exhibiting a decrease in size shortly before its extinction.

Rhagapodemus is a genus of extinct rodent from the Miocene to Pleistocene periods. Most species are known from European localities, although R. debruijni comes from India.

<i>Enhydrictis</i> Extinct genus of mustelid

Enhydrictis is a genus of extinct mustelid, belonging to the subfamily Galictinae. The type species, and best known, is Enhydrictis galictoides from the Pleistocene of Sardinia and Corsica. Some authors attribute species from mainland Eurasia to the genus, but this is disputed, with others considering the genus endemic to Sardinia-Corsica.

<span class="mw-page-title-main">Apodemini</span> Tribe of rodents

Apodemini is a tribe of muroid rodents in the subfamily Murinae. It contains two extant genera, one found throughout Eurasia and the other endemic to the Ryukyu Islands. Several fossil genera are also known from throughout Eurasia, including one large species (Rhagamys) that persisted on Sardinia and Corsica up until at least the first millennium BC, when it was likely wiped out by human activity.

Mus minotaurus is an extinct species of mouse native to Crete during the Late Pleistocene-Holocene. It descended from a Mus musculus -like ancestor that arrived on Crete during the late Middle Pleistocene, replacing Kritimys, a large rat-like rodent that inhabited Crete during the Early and Middle Pleistocene. Both Kritimys and the ancestor of Mus minotaurus, Mus bateae are found together in Stavrós Cave. The Mus batae-minotaurus lineage shows a tendency to increase in size with time, an example of island gigantism, with Mus minotaurus being one of the largest known members of the genus Mus, with a body mass of approximately 54 grams, over 3 times the size of its mainland ancestor. It was likely heavily predated upon by the extinct endemic Cretan owl, as evidenced by the abundance of its remains found in owl pellets. It inhabited the island alongside a species of elephant, the radiation of endemic Candiacervus deer, the Cretan otter, and the Cretan shrew. Mus minotaurus became extinct sometime during the Holocene epoch, with its remains apparently being found in Neolithic and early Bronze Age sites on the island. Its extinction may have been due to competition with the closely related house mouse introduced to the island by humans during the early Bronze Age.

References

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