Earliest hog-nosed skunk, Conepatus (Mephitidae, Carnivora), from the early Pliocene of Guanajuato, Mexico and origin of South American skunks

The hog-nosed skunk, Conepatus Gray, 1837, is one of the most widespread carnivorans in the New World, and one of the first to arrive in South America during the Great American Biotic Interchange (GABI). We report a basal hog-nosed skunk, Conepatus sanmiguelensis sp. nov., from the early Pliocene San Miguel de Allende Basin, Guanajuato State, central Mexico. The Mexican species greatly extends the first appearance of Conepatus from Irvingtonian to early Blancan in North America, more than doubling the time period of previously known appearances. The new species of Conepatus is also geographically closer to the Panamanian land bridge than previous records from the United States and northern Mexico, and permits a better sense of the faunal exchange during the early phase of the GABI. The new species is represented by two individuals, including a nearly complete skull and a partial mandible with most of the cheek teeth, as well as a large portion of the skeleton. Such a nearly complete representation of cranial, dental and skeletal materials enables us to conduct a species-level phylogenetic analysis. C. sanmiguelensis is characterized by its large size, condyloid foramen confluent with posterior lacerate foramen, presence of a P2, an M1 not very elongated and long trigonid on m1. This combination of primitive and derived characters suggests a phylogenetic position basal to a North American clade [C. sanmiguelensis (C. robustus, C. leuconotus)]. The new phylogenetic reconstruction suggests that Central and South American Conepatus form a sister group to the North American clade, and as such, must have equally ancient divergence time that dates back to at least 4-5 Ma. As a result, C. altiramus from coastal marine cliffs of Argentina should be seriously reconsidered to be from the Chapadmalal Formation in the early Pliocene, a notion dismissed by some recent authors. If this is correct, South American Conepatus represents the first known carnivoran immigrant during the first wave of the GABI. (C) 2008 The Linnean Society of London.