The dietary habits of extinct chelonioids are usually inferred from living relatives: cheloniids are considered mostly herbivorous, feeding on sea grasses or algae (e.g. Chelonia), or omnivorous, additionally ingesting invertebrates such as crustaceans and molluscs (e.g. Caretta); dermochelyids (represented solely by Dermochelys coriacea) are specialized jellyfish predators (Hendrickson 1980).