A Review of the Vertebrate Fauna of the Lower Jurassic Navajo Sandstone in Arizona

The Lower Jurassic Navajo Sandstone of northern Arizona and southern Utah has yielded a diverse assemblage of late Early Jurassic terrestrial tetrapods from eolian and associated paleoenvironments. Although rare, vertebrate body fossils are represented by specimens of tritylodonts, crocodylomorphs, sauropodomorphs, and basal theropods (including Segisaurus halli). The vertebrate ichnofossil record is diverse and includes synapsids (Brasilichnium), crocodylomorphs (cf. Batrachopus), ornithischians (Anomoepus), sauropodomorphs (Navahopus and Otozoum), theropods (Grallator, Anchisauripus, and Eubrontes), and several problematic morphs (“pterosaur”, “lacertilian”, and Trisauropodiscus). There is a high degree of concordance between the clades represented by the body fossils and ichnofossils. Taken together, they represent a typical Early Jurassic assemblage that is similar to other North American and foreign Early Jurassic terrestrial tetrapod assemblages, although a few forms are unique to the Navajo Sandstone (Segisaurus and Navahopus). The terminal Early Jurassic record of the Navajo Sandstone vertebrate assemblage suggests that little faunal change occurred through the course of the Early Jurassic Period in North America.