Quaternary gomphotheres (Mammalia: Proboscidea: Gomphotheriidae) from the continental shelf, Pearl Islands, Panama

Abstract

Fishermen have recovered four Quaternary proboscidean teeth from the continental shelf in the vicinity of the Pearl Islands, about 50–80 km offshore from the southern coast of Panama. Two upper third molars (M3) and one lower third molar (m3) are similar to comparable teeth of the Pleistocene gomphothere Cuvieronius based on the presence of 4½ to 5½ lophs/lophids that are either horizontal or slightly inclined to long axis of the tooth and rather complicated enamel with single trefoils, incipient double trefoils, and numerous small accessory cusps. Cuvieronius is also known from the Pleistocene El Hatillo and La Trinidaíta sites from the Azuero Peninsula in Panama. The teeth of Cuvieronius from the Pearl Islands are referred to C. hyodon following recent taxonomic revisions indicating a single pan-American species of this genus was present in both North America and South America. The oldest records of Cuvieronius are from early Pleistocene (early Irvingtonian) faunas in El Salvador, Florida, and New Mexico. Cuvieronius dispersed to South America in the early Pleistocene during the Great American Biotic Interchange, with the earliest record of C. hyodon on that continent from the early to middle Pleistocene (Ensenadan) Tarija fauna in Bolivia. The two late Pleistocene populations of C. hyodon in the Neotropical region have a disjunct biogeographic distribution, with the population from southern Mexico and Central America separated from the second population in the Andean highlands of Ecuador, Peru, and Bolivia by a distance of about 1000 km. The intervening region comprising the lowland tropics of northern South America was populated by the gomphothere Notiomastodon during the late Pleistocene, although Notiomastodon is also known from Andean localities in Ecuador and Peru. Two of the Cuvieronius teeth from the Pearl Islands were recovered in nets by shrimp fisherman from depths of about 90 m, likely indicating they date to the Last Glacial Maximum between 30 and 15 ka, when sea level was as much as 120 m lower than present and the Gulf of Panama was dry land. These teeth represent the first record of late Pleistocene fossils of terrestrial mammals from the continental shelf in Central America.