A Glimpse Through Time: Preliminary Report of the Andre’s Alcove Tracksite, Lower Jurassic Navajo Sandstone, Glen Canyon National Recreation Area, Utah

Abstract

In November 2018, a team of researchers from the National Park Service and the St. George Dinosaur Discovery Site documented fossil vertebrate tracks at the Andre’s Alcove Tracksite (AAT) in the Lower Jurassic (?190–185 Ma) Navajo Sandstone in Glen Canyon National Recreation Area, Utah. The tracks at the AAT were photo-documented for photogrammetric processing using Agisoft Photoscan Professional to enable the track surface to be studied remotely. Ichnotaxa already identified at the AAT include those of small ornithischian dinosaurs (Anomoepus), theropod dinosaurs (Grallator, Eubrontes), and protosuchian crocodylomorphs (Batrachopus). Vertebrate body fossils are rarer in the Navajo Sandstone than in underlying, earlier Jurassic strata; the AAT site therefore provides important insights into late Early Jurassic vertebrate diversity and behaviors at the onset of the Navajo Erg in the American Southwest.