[N] 2006 Re-evaluation dinosaurian fauna of the Wayan Formation, Idaho
Krumenacker, L.J. (2006) Ornithopods of the Wayan Formation (Albian) of East Idaho: A re-evaluation of the dinosaurian fauna. JVP 26(3) Abstracts pp.87
The dinosaurian fauna of the middle Albian Wayan Formation of east Idaho appears to be somewhat different from other Albian faunas of North America. As is typical for the Cretaceous, this fauna is ornithopod dominated; but by smaller ornithopods (possibly representing two taxa), rather than larger ones. Despite previous reports, there is no postcranial evidence for a Tenontosaurus-like iguanodont in the Wayan fauna. The associated skeleton previously reported as such belongs to an armored ornithischian. The only evidence for a Tenontosaurus-like animal comes from a single worn tooth recovered in the 1980’s.
The vast majority of ornithopod fossils come from small, long tailed, gracile animals similar to Hypsilophodon, Orodromeus, and Zephyrosaurus. Remains commonly occur as very fragmentary appendicular skeletal elements associated with partially articulated or associated vertebrae. Elongate caudal vertebrae have ventral grooves, lateral ridges, and distinct hexagonal articulations. Caudals are commonly associated with or encased in hypaxial and epaxial tendons. Previous reports suggested the presence of abundant dromaeosaurids in the Wayan, but it now appears more probable that the reputed dromaeosaur material belongs to these small ornithopods.
An enigmatic collection of associated caudal vertebrae may represent a second ornithopod type. These vertebrae come from an animal somewhat larger than the more common smaller ornithopod type. Caudals have circular articulations with tall, thin nueral spines. Distinct lateral grooves are present on the mid-caudals. Ossified tendons entirely encase the vertebrae and nueral spines. This animal is the largest probable ornithopod for which there is postcranial evidence from the Wayan.