| Redonda Formation | |
| Type: | Formation |
| Age: | Norian ~ |
| Period: | Norian |
| Prilithology: | Shale |
| Otherlithology: | Limestone, sandstone |
| Namedfor: | Redonda Mesa |
| Namedby: | Dobrovolny and Summerson |
| Year Ts: | 1946 |
| Region: | New Mexico |
| Coordinates: | 34.965°N -103.701°W |
| Paleocoordinates: | 9.9°N -43.2°W |
| Unitof: | Chinle Group |
| Subunits: | Duke Ranch, Quay, Red Peak, San Jon Creek & Wallace Ranch members |
| Underlies: | Entrada Formation |
| Overlies: | Bull Canyon Formation |
| Thickness: | NaNfeet |
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 5000km2.[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 | ||
| 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]