Ground Opossums of the genus Monodelphis are common on the grasslands of South America, with at least twenty known species, most of which are widespread in distribution. In June 1990 a joint expedition by the American Museum of Natural History and the Museum of Southwestern Biology at the University of New Mexico, was temporarily stranded at Santa Rosa de la Roca in eastern Bolivia, by a vehicle breakdown. This was not the area they intended to sample, but some traps were put down opportunistically on the border between a wet savanna and a forrest. These yielded three common Rodents and a single specimen of an unknown Opossum. No similar Opossum has been found in the intervening twenty years, making this specimen somewhat of a mystery.
In a paper published in the American Museum Novitates on 18 April 2012, Robert Voss of the Division of Vertebrate Zoology (Mammalogy) at the American Museum of Natural History, Ronald Pine of the Natural History Museum and Department of Ecology and Evolutionary Biology at the University of Kansas, and Sergio Solari of the Instituto de Biología at the Universidad de Antioquia in Medellín, Colombia, formally describe the Santa Rosa de la Roca Opossum for the first time; the specimen had been mentioned in a number of previous studies, but never previously given a full taxonomic description.
The Santa Rosa de la Roca Opossum. Voss et al. (2012).
The specimen is named as Monodelphis sanctaerosae, the Santa Rosa de la Roca Opossum. It is a 108 mm long grey Opossum with reddish-brown fur on the sides of its head and around its ears. It is considerably smaller than its closest relatives, Monodelphis domestica and Monodelphis glirina.
The conservation status of Monodelphis sanctaerosae is unclear; only a single specimen has ever been captured, from a location which has not been well sampled by biologists. It is unclear how abundant the species is at the type location, or if the species is found anywhere else.
Map of Bolivia showing the known distributions of Monodelphis domestica, Monodelphis glirina and Monodelphis sanctaerosea. The numbers provide a key to museum specimens. Voss et al. (2012).
See also New Caviomorph Rodents from the Early Oligocene Tinguiririca Fauna of the Andean Main Range of central Chile, A new Ground Sloth from the Late Miocene of Argentina, The origin of domestic dogs, Three new species of Tapir from the Early Eocene of Pakistan and Mammals on Sciency Thoughts YouTube.
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