Coloradisaurus (meaning "Los Colorados lizard") is a genus of massospondylid sauropodomorph dinosaur. It lived during the Late Triassic period (Norian stage) in what is now La Rioja Province, Argentina. It is known from two specimens collected from the Los Colorados Formation of the Ischigualasto-Villa Unión Basin. Taxonomy Coloradisaurus brevis was originally named Coloradia brevis by José Bonaparte in 1978, but that genus name was preoccupied by the pine moth Coloradia, so it needed a replacement name. In 1983, David Lambert used the name Coloradisaurus for the genus, but did not indicate it was a replacement or diagnose it. Lambert had gotten the name from Bonaparte in a personal communication and mistakenly thought that Bonaparte had already published it. Peter Galton was the next to use the name Coloradisaurus in 1990, which he credited to Lambert, when he gave the taxon a diagnosis in his review of prosauropods in The Dinosauria. Authorship of Coloradisaurus has traditionally been attributed to Lambert, but in 2020, Greenfield et al. judged Lambert's use of the name to be a nomen nudum. They concluded that authorship should be attributed to Galton, who was the first to use the name Coloradisaurus in a way that met the requirements of the ICZN. Description The holotype of Coloradisaurus (PVL 3967) is a mostly complete skull found associated with an undescribed partial skeleton. While the right side of the skull is well-preserved with almost all bones intact, the left side is distorted and missing more bones. The holotype individual has been estimated to have been 3 m (10 ft) long with a mass of 70 kg (150 lb). A referred specimen (PVL 5904) is a partial skeleton including the most of the dorsal vertebrae and parts of the pectoral and pelvic girdles and limbs. All of this material was discovered in 1971 at the La Esquina locality in the upper section of the Los Colorados Formation near Pagancillo, La Rioja Province, Argentina. The top of the Los Colorados Formation has been dated to 213 Ma, which would place Coloradisaurus in the Norian stage of the Late Triassic. Phylogeny Coloradisaurus was classified as a plateosaurid in the original description by Bonaparte, but this pre-dated the use of phylogenetic analyses in paleontology. He later became opposed to cladistics and continued to consider Coloradisaurus a plateosaurid without testing its phylogenetic position. The analyses of Galton (1990), Galton & Upchurch (2004), and Upchurch et