ABSTRACT: The Long Walk Quarry and Tracksite: A New Chapter in the Story of Colorado Plateau Dinosaurs

Frank L. DeCourten

The Early Cretaceous is a mysterious interval in the history of the Mesozoic terrestrial ecosystem in the Colorado Plateau region. The spectacular abundance of dinosaur remains in the Late Jurassic (Morrison Formation) and the Late Cretaceous ("Mesaverde" Group and equivalents), coupled with the striking contrasts between the faunas of these units, poses many intriguing questions concerning evolutionary dynamics, dinosaur phylogeny, and ecological history of the intervening interval.

The Long Walk Quarry in central Utah yields abundant dinosaur material from the Cedar Mountain Formation (Albian-Aptian), a unit heretofore considered to be only sparsely fossiliferous. Taxa documented from the site thus far include the small sauropod Pleurocoelus and an Acrocanthosaurus-like carnosaur. Neither of these taxa have been previously identified in the Colorado Plateau. In addition, a tracksite has been discovered in this same unit which yields an ichnofauna dominated by ornithopod dinosaur tracks. Collectively, the new fossil material and tracks from the Cedar Mountain Formation at the Long Walk Quarry represent the single most important source of data on Lower Cretaceous dinosaurs in the Colorado Plateau Province. Ongoing investigations at the site will ultimately illumin te a poorly understood phase in the regional history of Mesozoic reptiles.

AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990