Austroposeidon magnificus

Austroposeidon is a titanosaurian sauropod dinosaur genus from Brazil's Late Cretaceous Presidente Prudente Formation. Austroposeidon magnificus is the only species found there (meaning "Magnificent Southern Poseidon"). Palaeontologist Llewellyn Ivor Price found the specimen in the Campanian-Maastrichtian Presidente Prudente Formation of the Bauru Group in 1953, but the bones were not documented until 2016. According to the excellent sandstone in which the specimen was discovered, the animal was most likely preserved by a crevasse splay on a floodplain. Unfortunately, the location where the specimen was discovered has since been destroyed by urban expansion.

Austroposeidon was a gigantic sauropod found in Brazil, with the one known specimen, an adult, measuring around 25 meters in length (82 ft). Austroposeidon was a titanosaur because the vertebrae lack hyposphene-hypantrum articulations, the cervical and dorsal vertebrae lack forked neural spines, and the internal bone texture is camellate (punctuated by many small air chambers).

Austroposeidon was confirmed to be a new genus based on a number of autapomorphies (traits unique to known fossils) in the vertebrae: the thirteenth cervical vertebra has columnar centropostzygapophyseal laminae, and its rear centrodiapophyseal lamina splits into two prongs; the first dorsal vertebra has front and back centrodiapophyseal laminae that curve downwards and outwards, and its diapophysis stretches down to the top margin of the centrum; and the frontmost part of the spinoprezygapophyseal laminae forks in the dorsal vertebrae positioned towards the back of the torso. Austroposeidon also has a rare mix of additional vertebrate characteristics not found in other titanosaurs.