First named and defined by Wilson and Sereno (1998) and Sereno (1998), the taxon has not been re-defined in any way since (Upchurch et al. 2004). Both textual variants of the definition are given below, as they were published in the same year. Camarasauromorpha, a node-based group with similar taxonomic content, was named independently by Salgado et al. (1997), who only used node-based definitions. Macronaria, in contrast, is a stem-based definition that is part of a node-stem triplet (for additional discussion, see Taylor and Naisch 2005).  The active definition is a first-order revision that uses species as specifiers.