Late Triassic Nonmarine Vertebrate and Invertebrate Trace Fossils and the Pattern of the Phanerozoic Record of Vertebrate Trace Fossils

Abstract

The diverse ichnofaunas of the Late Triassic have been studied for almost 200 years. During the Late Triassic, facies favorable for the preservation of trace fossils were the result of low sea levels, monsoonal climates and the development of extensive depositional basins as Pangea began to fragment. The most abundant vertebrate trace fossils in the Late Triassic are tetrapod tracks, including Brachychirotherium, Chirotherium, “Parachirotherium,” Synaptichnium, Atreipus, Grallator, Eubrontes, Banisterobates, Trisauropodiscus, Evazoum, Tetrasauropus, Pseudotetrasauropus, Eosauropus, Apatopus, Batrachopus, Rhynchosauroides, Gwyneddichnium, Procolophonichnium, Chelonipus, Brasilichnium and Dicynodontipus. There are five tetrapod footprint biochrons of Triassic age that can be identified across the Pangaean footprint record. Coprolites are the second most abundant vertebrate trace fossils in the Late Triassic and include Heteropolacopros, Alococoprus, Dicynodontocopros, Liassocoprus, Saurocoprus, Strabelocoprus, Malericoprus, Falcatocoprus and Revueltobromus. Coprolites are useful in biochronology in the Late Triassic. Consumulites, dentalites (new term for bite marks), and burrows are moderately common in the Late Triassic. Nests and gastroliths are rare. All groups of vertebrate trace fossils demonstrate different diversity and abundance patterns through the Phanerozoic. Most vertebrate trace fossils have their earliest occurrences in the Devonian. The early Permian is an acme for both tracks and coprolites. The Late Triassic yields abundant tracks and coprolites, and tracks are also common in the Early Jurassic. The Jurassic and Cretaceous represent the times with the greatest diversity of vertebrate traces (tracks, coprolites, consumulites, dentalites, nests and gastroliths). The Quaternary also represents a time of vertebrate ichnological diversity (tracks, coprolites, regurgitalites, nests and burrows).