Late Cenozoic land mammals from Grenada, Lesser Antilles island-arc. American Museum novitates ; no.3302

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New York, NY : American Museum of Natural History
We report on a small collection of late Cenozoic fossil vertebrates recovered from a lahar (mudflow) deposit at Locality 12° North on the southern coast of Grenada. ⁴⁰K/⁴⁰Ar-dated hornblende concentrate from the lahar deposit yielded age estimates of 2.6-3.7 Ma (late Pliocene). Although these estimates date crystallization of the hornblende and not the lahar event, the latter is unlikely to be substantially younger. The contained fauna is here regarded as latest Pliocene or slightly younger. Dental specimens in the collection are readily referable to Hydrochaeridae (Rodentia, Caviida) and Megalonychidae (Xenarthra, Phyllophaga), groups heretofore unknown on this island. The capybara, Hydrochaeris gaylordi, new species, differs from extant Hydrochaeris hydrochaeris in the conformation of the maxillary second molar. The sloth teeth (two caniniforms, one molariform) notably differ from one another in size, but whether they represent one species or two cannot be decided on this evidence. Because of the limitations of the material, attribution of the specimens to subfamily or tribe within Megalonychidae is also uncertain. Megalonychid sloths have never been found previously on any of the Lesser Antilles, although they formed part of the terrestrial vertebrate fauna of most of the Greater Antilles. Curaçao is the only other island in the Caribbean Sea that has yielded sloth and capybara fossils. Sloths and capybaras might have reached that island as well as Grenada by short-distance over-water transport, perhaps during a time of lowered sea level. A late land connection with South America is perhaps possible, but this would need to be confirmed with suitable geological evidence.
20 p. : ill., map ; 26 cm.
Includes bibliographical references (p. 18-20).