Arizona’s Jurassic Fossil Vertebrates and the Age of the Glen Canyon Group

Most fossil vertebrates of Jurassic age from Arizona are derived from the Glen Canyon Group on the southern Colorado Plateau in the northeastern part of the state. Glen Canyon Group strata of Jurassic age in Arizona that yield fossils include the upper Dinosaur Canyon and the Whitmore Point members of the Moenave Formation, the Kayenta Formation, and the Navajo Sandstone. All of these units yield both trace (principally dinosaur footprint) and body fossils of tetrapods. To date, only the Kayenta Formation fauna is particularly diverse (more than 10 taxa), and the Kayenta fauna is one of the best known Dawan (Early Jurassic: Sinemurian) tetrapod faunas in North America, and includes numerous type specimens, representing important records of tritylodonts, theropod dinosaurs, amphibians, turtles, and mammals. Non-Glen Canyon Group records of Jurassic vertebrates from northern Arizona are limited to scattered occurrences of footprints in the Middle-Upper Jurassic Summerville Formation and a single documented Apatosaurus vertebra from the Morrison Formation. The only Jurassic vertebrates from southern Arizona are fragmentary tetrapods from the Gardner Canyon Formation in the Santa Rita Mountains and undescribed osteichthyans from Upper Jurassic marine strata in the Chiricahua Mountains.