Carletonomys
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Carletonomys cailoi Temporal range: (Ensenadan) ~1.2–0.8 Ma |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Rodentia |
| Family: | Cricetidae |
| Subfamily: | Sigmodontinae |
| Tribe: | Oryzomyini |
| Genus: |
†Carletonomys Pardiñas, 2008 |
| Species: | †C. cailoi |
| Binomial name | |
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Carletonomys cailoi Pardiñas, 2008 |
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Carletonomys cailoi is an extinct rodent from the (Ensenadan) of Buenos Aires Province, Argentina. Although known only from a single maxilla (upper jaw) with the first molar, its features are so distinctive that it is placed in its own genus, Carletonomys. Discovered in 1998 and formally described in 2008, it is part of a well-defined group of oryzomyine rodents that also includes Holochilus, Noronhomys, Lundomys, and Pseudoryzomys. This group is characterized by progressive semiaquatic specializations and a reduction in the complexity of molar morphology.
The single known molar is high-crowned (hypsodont) and flat-crowned (planar) and is distinctive in lacking the ridge that connects the front to the middle part of the molar, the anterior mure, and in the configuration of another ridge, the mesoloph. Carletonomys was probably herbivorous and lived in a wet habitat.
Carletonomys cailoi was discovered in 1998 in a silt deposit in San Cayetano Partido, southeastern Buenos Aires Province. The stratigraphic context suggests this locality is slightly over 1 million years old (Ensenadan South American Land Mammal Age), making Carletonomys the oldest known oryzomyine. The single known specimen is now in the collections of the Museo de La Plata. It was initially referred to the genus Noronhomys, which is currently known only from the island of Fernando de Noronha off northeastern Brazil, but in 2008 Argentinean mammalogist Ulyses Pardiñas established it as the holotype of a new genus and species of rodent in a publication in the Journal of Mammalogy. The generic name, Carletonomys, combines the name of American mammalogist Michael Carleton with the Ancient Greek μυς mys "mouse" and the specific name, cailoi, honors Argentinean biologist Carlos "Cailo" Galliari.
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