A photo documentation of bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation, USA

Abstract

Bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation are rare, forming only about 15% of the dinosaur specimens. Nevertheless, one of them was among the first dinosaurs named from what was then the ‘’Atlantosaurus Beds’’ of Colorado. Collecting and restudy for 140 years has in­creased the diversity from the initial 1877 discovery to the currently valid four genera and six species, viz., Fruitadens haagaroum, Nanosaurus agilis, Camptosaurus dispar, C. aphanoecetes, Dryosaurus altus, and D. elderae, which we briefly review. We demonstrate that the enigmatic Nanosaurus agilis is the senior name for Drinker nisti, Othnielosaurus consors, and Othnielia rex. In addition, a new species, Dryosaurus elderae is proposed for the Dryosaurus specimens from Dinosaur National Monument that are characterized by elongate cervical verebrae and a long, low ilium among other features.