Phytosaur tooth-New Mexico 005

Taxa: Indeterminate Phytosaur

Geology: Redonda formation

Age: Triassic

Locality: Quay County, New Mexico

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Redonda formation

The Redonda Formation is a Late Triassic geologic formation exposed in eastern New Mexico. It consists mainly of interbedded red-brown sandstone, mudstone, and shale, with some limestone layers, and ranges from about 25 to 425 feet (7.6–129.5 m) thick. The formation was deposited in and around a large ancient lake covering roughly 5,000 square kilometers (1,900 sq mi). Fossils found include abundant invertebrates, fish, amphibians, early reptiles, and notable theropod (dinosaur) tracks, though plant fossils are rare. The Redonda Formation conformably overlies the Bull Canyon Formation and underlies the Entrada Formation.

Phytosaurs

Phytosaurs from the Redonda Formation, especially the genus Redondasaurus, were large, semi-aquatic, crocodile-like reptiles from the Late Triassic. Redondasaurus skulls from this formation could exceed 1.2 meters in length, indicating individuals up to 6.4 meters (21 feet) long. They had long snouts, robust armor, and unique features such as concealed supratemporal fenestrae and thickened osteoderms. Redondasaurus is considered one of the most derived North American phytosaurs and is a key index fossil for the Redonda Formation’s Apachean age. Fossils are often found in channel and lake deposits within the formation.