A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: a reassessment of dinosaur origin and phylogeny

A new early dinosaur species, Chromogisaurus novasi, has been discovered in the Late Triassic Ischigualasto Formation of Argentina, challenging traditional views on dinosaur diversity and dominance. This find reveals that dinosaurs first appeared as a diverse group, though numerically minor, with their numerical rise over other tetrapods occurring diachronously after an initial phase of low abundance but high diversity. Phylogenetic analysis places Chromogisaurus at the base of Sauropodomorpha within the Guaibasauridae family, introducing it as the first member of this group and naming a new subfamily, Saturnaliinae, which includes Chromogisaurus and Saturnalia. The study also reclassifies Eoraptor as the sister-taxon to Neotheropoda and herrerasaurids as non-eusaurischian saurischians, providing significant insights into early dinosaur evolution.

Ezcurra, M. D. (2010). A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: a reassessment of dinosaur origin and phylogeny. Journal of Systematic Palaeontology, 8(3), 371–425. https://doi.org/10.1080/14772019.2010.484650