Sauropoda was initially defined as both a node- and stem-based group by Salgado et al. (1997) and McIntosh (1997), respectively. The node-based definition focuses on the basal sauropod Vulcanodon. The stem-based definition was initially constructed when at least a core group of prosauropods were regarded as monophyletic. With most basal sauropodomorphs redistributed as successive stem taxa, a stem-based definition for Sauropoda must be retooled to exclude the most derived forms. Otherwise Sauropoda will subsume many taxa formerly considered prosauropods (e.g. Yates and Kitching 2003).
The active definition is a first-order revision of McIntosh (1997), Wilson and Sereno (1998) and Sereno (1998). Two external specifiers, Mussaurus patagonicus and Jingshanosaurus xinwaensis (Pol and Powell 2005, Zhang and Yang 1994) were used to delimit the taxonomic content of Sauropoda. There is significant evidence that these two well preserved and documented sauropodomorphs are among the closest to Sauropoda. Their postcranial skeletons, however, are remarkably similar to that of other basal sauropodomorphs.