New Record of Capybara (Rodentia: Caviidae: Hydrochoerinae) from the Pleistocene of San Diego County, California with Remarks on Their Biogeography and Dispersal in the Pleistocene of Western North America

We describe a new species of capybara from late Pleistocene deposits (Rancholabrean NALMA) in northern San Diego County, California, USA which tentatively dates to Marine Isotope Stage (MIS) 5 interglacial (~130 ka to 80 ka). The specimen represents a new species of Hydrochoerus based on morphological characters of the upper incisor (I1) and the upper (maxillary) third molar (M3). Hydrochoerus hesperotiganites sp. nov. differs from other described species of Hydrochoerus in its larger size, wider skull roof, more robust zygomatic process of the maxilla and descending zygomatic process of the lacrimal and in details of the otic region. The new species is the only confirmed record of fossil Hydrochoerus in North America and is the northwestern-most record of any capybara in North America. All previous records of fossil capybara from North America represent one of two extinct genera, Neochoerus or Phugatherium. Northward dispersal of capybaras from central and southern México probably occurred along the coasts of Sinaloa and Sonora, entering the north or northeast flowing drainages which entered the Gulf of California, then further north into the San Simon drainage to the Gila River and ultimately into the Colorado River, or directly northward along the coast of Sonora to the mouth of the Colorado River.lsid: urn:lsid:zoobank.org:pub:BD2DA9EB-32EF-4761-8551-E585D6AF317C