The Redonda Formation is a geologic formation exposed in eastern New Mexico.^[1] It contains vertebrate fossils of the late Triassic Period.^[2] Fossil theropod tracks have been reported from the formation.^[3]

The formation consists of interbedded fine-grained red-brown sandstone and mudstone. It conformably overlies the Bull Canyon Formation^[4] and underlies the Entrada Formation.^[2]

The formation is interpreted as having been deposited in a lake with an area of about 5,000 square kilometres (1,900 sq mi).^[4]

The formation has few fossil plants, with only Neocalamites reported, but it contains abundant invertebrate fossils (conchostracans and ostracods) and a diverse assemblage of vertebrate fossils.^[4][3]

fish of the Redonda Formation
Taxa	Presence	Notes	Images
Cionichthys	Skull fragments	A redfieldiid
Ceratodus		A lungfish
Coelacanthidae indet.	Fragmentary material	Possibly assignable to Chinlea or Quayia
Hemicalypterus	scales	A dapediid
Semionotus	Abundant, found in large deathbeds	A semionotid
Synornichthys	Skull fragments	A redfieldiid

Stereospondyls of the Redonda Formation
Taxa	Presence	Notes	Images
Apachesaurus	Numerous specimens	A metoposaurid, possibly juveniles of Koskinonodon

Archosauriforms of the Redonda Formation
Taxa	Presence	Notes	Images
Apachesuchus	Osteoderms	An aetosaur similar to Neoaetosauroides
Redondasaurus	Numerous skulls and other skeletal remains	A phytosaur
Redondasuchus	Osteoderms and other fragments	A typothoracisine aetosaur related to Typothorax
Redondavenator	Snout bones and a scapulocoracoid	A large, predatory basal crocodylomorph
Vancleavea	Osteoderms	An unusual non-archosaurian archosauriform

The unit was first named as the Redonda Member of the Chinle Formation by Dobrovolny and Summerson in 1947.^[1] Griggs and Read raised the unit to formation rank in 1959, and also assigned an age of late Triassic based on the presence of tracks of a bipedal dinosaur and of a phytosaur skull.^[2]

• List of dinosaur-bearing rock formations
  • List of stratigraphic units with theropod tracks

• Dobrovolny, Ernest; Summerson, C.H. (1947). "Geology of northwestern Quay County, New Mexico". U.S. Geological Survey Oila Nd Gas Investigations Map. OM-62. doi:10.3133/om62.
• Griggs, R.L.; Read, C.B. (1959). "Revisions in Stratigraphic Nomenclature in Tucumcari-Sabinoso Area, Northeastern New Mexico: GEOLOGICAL NOTES". AAPG Bulletin. 43 (8): 2003–2007. doi:10.1306/0BDA5E8E-16BD-11D7-8645000102C1865D.
• Lucas, S.G.; Hunt, A.P. (1989). "Revised Triassic stratigraphy in the Tucumcari basin, east-central New Mexico". In Lucas, S.G.; Hunt, A.P. (eds.). Dawn of the age of dinosaurs in the American southwest. New Mexico Museum of Natural History and Science. pp. 150–170. Retrieved 17 September 2020.
• Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.