Opisthocoelicaudia skarzynskii was a 12 m-long (39 ft.) sauropod that was discovered in 1965 in the Nemegt Basin of the Gobi Desert of Mongolia by scientists from one of the numerous Polish-Mongolian Palaeontological Expeditions. The skeleton was missing the skull and neck vertebrae.
This dinosaur was a land dwelling animal that was able to bear the hot sub-tropical sun in the open, humid and seasonal bottomland forests that existed in Mongolia some 70 million years ago.
Opisthocoelicaudia was not described until 1977 and was at the time thought to be a type of camarasaur. Scientists now think it belongs to the group of sauropods called the titanosaurs. Its name, Opisthocoelicaudia, is derived from Greek and Latin words, and essentially means "hollow from behind tail". This refers to the type of the vertebrae in the front part of the tail, where the posterior end (facing rearward) of the vertebrae is concave in shape and the anterior end (facing forward) is convex. Opisthocoelicaudia skarzynskii is the only species in the genus.
Despite its enormous weight, which is estimated at about 30 t (33 tn.), Opisthocoelicaudia held its tail well off the ground when walking. It may have used its tail as a prop, thereby allowing it to rear up in a bipedal stance to browse high up in the tree crowns. Like most sauropods, it probably required up to hundreds of kilograms of forage on a daily basis to meet its nutritional requirements.