size as seen in all later sauropods: The wrist bones were broader and thicker to support more weight, whereas the femur was elliptical in cross section. The vertebrae bear high neural spines and well developed hyposphene-hypantrum articulations which add rigidity to the trunk. The first toe of the hind foot already bears a large claw longer than the first metatarsal; however, this claw was not sickle shaped as seen in later sauropods. The femur was slightly sigmoidal (S-curved) in lateral view rather than straight as in other sauropods. Classification A cladistic analysis by Yates and Kitching recognizes Antetonitrus as a basal sauropod, occupying a position between more derived animals such as Isanosaurus or Vulcanodon, and more basal sauropods like Melanorosaurus. The back vertebrae are extremely similar to Lessemsaurus from South America, while the limb bones are similar to Blikanasaurus, another stocky early sauropod from South Africa. However, these animals were not included in a cladistic analysis with Antetonitrus because they are poorly known. Apaldetti et al. (2018) erected Lessemsauridae, a clade containing Antetonitrus, Lessemsaurus and Ingentia. Their cladogram is reproduced below: The following cladogram shows the position of Antetonitrus within Massopoda, according to Oliver W. M. Rauhut and colleagues, 2020: Paleogeography While Antetonitrus is not the earliest sauropod from a phylogenetic standpoint, it is currently one of the oldest known sauropod chronologically, or rather tied for that distinction with other early sauropods from the same formation, like Melanorosaurus and Blikanasaurus. Fossils of these animals were recovered from the Elliot Formation. Initially it was thought to have been recovered from the Lower Elliot Formation which dates to the Norian stage of the Late Triassic, or approximately 221 to 210 million years ago. Later studies indicate that it was actually recovered from the Early Jurassic Upper Elliot Formation. Before Antetonitrus and the other animals recovered from the Elliot Formation were recognized as sauropods, the oldest known sauropod had been Isanosaurus from the Rhaetian stage of Thailand. Early sauropods and their sauropodomorph relatives were found around the world as all of the continents were at the time united into the single supercontinent, Pangaea, which made dispersal across the entire terrestrial world possible. References External links Post about Antetonitrus on the Dinosaur Mailing List , written by Adam Yates Sauropods of Africa Early Jurassic sauropods Early Jurassic dinosaurs of Africa Fossils of South Africa Fossil taxa described in 2003 Taxa named by James Kitching