Biology:Coloradisaurus

Coloradisaurus; Temporal range: Norian; ~213 Ma PreЄ Є O S D C P T J K Pg N ↓
	Diagram showing known skull elements; shaded parts represent missing bones
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Family:	†Massospondylidae
Genus:	†Coloradisaurus; Galton, 1990
Type species
	†Coloradisaurus brevis; (Bonaparte, 1978)
Synonyms
	Coloradia brevis; Bonaparte, 1978 (preoccupied by Coloradia Blake, 1863); "Coloradisaurus"; Lambert, 1983 (nomen nudum);

Short description: Extinct genus of dinosaurs

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,^[4] but that genus name was preoccupied by the pine moth Coloradia,^[5] 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.^[6] Lambert had gotten the name from Bonaparte in a personal communication and mistakenly thought that Bonaparte had already published it.^[3] 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.^[2]^[3] 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.^[3]

Description

The holotype of Coloradisaurus (PVL 3967) is a mostly complete skull found associated with an undescribed partial skeleton.^[4] While the right side of the skull is well-preserved with almost all bones intact, the left side is distorted and missing more bones.^[7] The holotype individual has been estimated to have been 3 m (10 ft) long with a mass of 70 kg (150 lb).^[8] 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.^[9] Like Lufengosaurus, it have the angle between the pterygoid and quadratojugal rami nearly 90°. There is also a possibility that the postorbital bones of Coloradisaurus and Sarahsaurus are similar, but due to the deformation of the skull this is difficult to say.^[10]

All material of Coloradisaurus was discovered in 1971 at the La Esquina locality in the upper section of the Los Colorados Formation near Pagancillo, La Rioja Province, Argentina .^[4]^[7]^[9] The top of the Los Colorados Formation has been dated to 213 Ma,^[1] 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,^[4] but this pre-dated the use of phylogenetic analyses in paleontology. He later became opposed to cladistics^[11] and continued to consider Coloradisaurus a plateosaurid without testing its phylogenetic position.^[12] The analyses of Galton (1990), Galton & Upchurch (2004), and Upchurch et al. (2007) found it to be a plateosaurid, supporting Bonaparte's placement.^[2]^[13]^[14] However, the analyses of Benton et al. (2000) and Yates (2003) recovered it in a polytomy with other basal sauropodomorphs or as a massospondylid, respectively.^[15]^[16] Subsequent analyses such as Yates et al. (2010), Apaldetti et al. (2013; 2014), Wang et al. (2017), and Müller (2020) have reached the consensus that Coloradisaurus is a massospondylid most closely related to Lufengosaurus and Glacialisaurus.^[7]^[9]^[17]^[18]^[10]^[19] These three taxa share four synapomorphies found in the metatarsals and femur.^[9]