Denver's deepest dinosaur.

We describe and interpret an Upper Cretaceous (Maastrichtian) ornithischian dinosaur bone from a core drilled in City Park of Denver, Colorado. The bone is identifiable as a vertebral centrum based on its morphology, including the presence of the impression of the neural canal on its dorsal surface, thin cortex, and dense spongy internal structure. An associated bone piece that occurs just above the centrum is interpreted as part of a neural arch that shares similarities to those of ornithopod dinosaurs such as Thescelosaurus or Edmontosaurus. The bone occurs near the top of a sequence capped by carbonaceous mudstone, interpreted to represent a pond- or swamp-like environment. To place this herbivorous dinosaur into context, we provide new geochronologic and stratigraphic constraints for important fossil sites from the metropolitan Front Range. Because the City Park dinosaur occurs ~232.5 m (~763 feet) below the surface, it represents the deepest and the oldest dinosaur known from the city of Denver, with an estimated age of 67.5 Ma. This fossil underscores the highly fossiliferous nature of the entire D1 Sequence (Denver Formation) and increases the diversity of dinosaurs known from the Denver metropolitan area. [ABSTRACT FROM AUTHOR]