| Redonda Formation | |
|---|---|
| Stratigraphic range:Norian ~221–206 Ma | |
| Type | Formation |
| Unit of | Chinle Group |
| Sub-units | Duke Ranch, Quay, Red Peak, San Jon Creek & Wallace Ranch members |
| Underlies | Entrada Formation |
| Overlies | Bull Canyon Formation |
| Thickness | 25–425 feet (7.6–129.5 m) |
| Lithology | |
| Primary | Shale |
| Other | Limestone,sandstone |
| Location | |
| Coordinates | 34°57′54″N103°42′04″W / 34.965°N 103.701°W /34.965; -103.701 |
| Approximate paleocoordinates | 9°54′N43°12′W / 9.9°N 43.2°W /9.9; -43.2 |
| Region | New Mexico |
| Country |  United States |
| Type section | |
| Named for | Redonda Mesa |
| Named by | Dobrovolny and Summerson |
| Year defined | 1946 |
  Redonda Formation (the United States) Show map of the United States Redonda Formation (New Mexico) Show map of New Mexico | |
TheRedonda Formation is a geologicformation exposed in easternNew Mexico.[1] It contains vertebratefossils of thelate TriassicPeriod.[2] Fossiltheropod tracks have been reported from the formation.[3]
The formation consists of interbedded fine-grained red-brownsandstone andmudstone. It conformably overlies theBull Canyon Formation[4] and underlies theEntrada 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 onlyNeocalamites reported, but it contains abundant invertebrate fossils (conchostracans andostracods) and a diverse assemblage of vertebrate fossils.[4][3]
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| fish of the Redonda Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Notes | Images | |
| Skull fragments | Aredfieldiid |  | ||
| Alungfish | ||||
Coelacanthidae indet. | Fragmentary material | Possibly assignable toChinlea orQuayia | ||
| scales | Adapediid | |||
| Abundant, found in large deathbeds | Asemionotid | |||
| Skull fragments | A redfieldiid | |||
| Stereospondyls of the Redonda Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Notes | Images | |
| Numerous specimens | Ametoposaurid, possibly juveniles ofKoskinonodon |  | ||
| Synapsids of the Redonda Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Notes | Images | |
| teeth | ||||
| Archosauriforms of the Redonda Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Notes | Images | |
| Osteoderms | Anaetosaur similar toNeoaetosauroides |   | ||
| Numerous skulls and other skeletal remains | ||||
| Osteoderms and other fragments | A typothoracisine aetosaur related toTypothorax | |||
| Snout bones and ascapulocoracoid | A large, predatory basalcrocodylomorph | |||
| Osteoderms | An unusual non-archosaurianarchosauriform | |||
The unit was first named as the Redonda Member of theChinle 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 aphytosaur skull.[2]