The Redonda Formation is a geologic formation exposed in eastern New Mexico.Dobrovolny and Summerson 1947 It contains vertebrate fossils of the late Triassic Period.Griggs and Read 1959 Fossil theropod tracks have been reported from the formation.Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
Description The formation consists of interbedded fine-grained red-brown sandstone and mudstone. It conformably overlies the Bull Canyon FormationLucas and Hunt 1989 and underlies the Entrada Formation.
The formation is interpreted as having been deposited in a lake with an area of about .
Fossils 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.
Vertebrate fauna
Fish fish of the Redonda Formation Taxa Presence Notes ImagesCionichthys Skull fragments A redfieldiidCeratodus A lungfishCoelacanthidae indet. Fragmentary material Possibly assignable to Chinlea or QuayiaHemicalypterus scales A dapediidSemionotus Abundant, found in large deathbeds A semionotidSynornichthys Skull fragments A redfieldiid
Stereospondyls Stereospondyls of the Redonda Formation Taxa Presence Notes ImagesApachesaurus Numerous specimensA metoposaurid, possibly juveniles of Koskinonodon Synapsids Synapsids of the Redonda Formation Taxa Presence Notes ImagesRedondagnathusteethA trirachodontid cynodont Archosauriforms Archosauriforms of the Redonda Formation Taxa Presence Notes ImagesApachesuchus OsteodermsAn aetosaur similar to NeoaetosauroidesRedondasaurusNumerous skulls and other skeletal remainsA phytosaurRedondasuchus Osteoderms and other fragmentsA typothoracisine aetosaur related to Typothorax Redondavenator Snout bones and a scapulocoracoid A large, predatory basal crocodylomorphVancleaveaOsteodermsAn unusual non-archosaurian archosauriform
History of investigation The unit was first named as the Redonda Member of the Chinle Formation by Dobrovolny and Summerson in 1947. 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.
See also List of dinosaur-bearing rock formations List of stratigraphic units with theropod tracks
References
Bibliography
Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. .