Ribodon is an extinct genus of manatee that lived around South America (Ituzaingó Formation, then described as Entrerriana Formation, Argentina, Solimões Formation, Brazil and Urumaco Formation, Urumaco, Venezuela) during the Tortonian (Mayoan to Huayquerian in the South American land mammal ages). The type species is R. limbatus. Ribodon is considered the direct ancestor of the Trichechus genus to which all modern manatees belong and was the first manatee to exhibit supernumerary molars that were replaced throughout life, indicating a diet of abrasive plants. Ribodon is hypothesized to have inhabited both coastal and inland freshwater regions; however, in which of the two it originated is unknown. References Prehistoric placental genera Miocene sirenians Miocene mammals of South America Huayquerian Chasicoan Mayoan Neogene Argentina Fossils of Argentina Ituzaingó Formation Neogene Brazil Fossils of Brazil Neogene Venezuela Fossils of Venezuela Fossil taxa described in 1883 Taxa named by Florentino Ameghino