Atopodentatus is an extinct genus of marine reptile, possibly basal sauropterygian, known from the early Middle Triassic (Pelsonian substage, Anisian stage) of Luoping County, Yunnan Province, southwestern China. It contains a single species, Atopodentatus unicus. It is thought to have lived between 247 and 242 million years ago, during the Middle Triassic period, about six million years after the Permian extinction. Atopodentatus was herbivorous marine reptile, usually marine reptiles are omnivores or carnivores.