Opisthocoelicaudia

Opisthocoelicaudia (from Greek οπισθή, opisthe, κοιλος, koilos, and Latin cauda, meaning posterior cavity tail) was 12-metre-long (39 feet) sauropod dinosaur of the Late Cretaceous Period discovered in Mongolia in 1965 by Polish and Mongolian scientists in what is now the Gobi Desert. In the Cretaceous, Mongolia had instead lush jungles and murky marshes, which Opisthocoelicaudia might have waded in. The genus was described and named in 1977 by Borsuk-Białynicka as a new type of camarasaur, but studies such as Salgado and Coria (1993) find it to be a saltasaurid titanosaur instead. Its skull and neck were missing and its carcass had apparently been buried before disintegrating. Borsuk-Białynicka suggested tyrannosaurid scavengers had fed on the carcass, eating the head and neck and leaving noticeable tooth marks on the pelvis and femur. Scientists cannot be sure what its head or neck looked like, because neither was ever recovered.