Wayan Formation

Sediments are dominantly floodplain mudstones (many having undergone extensive pedogenic processes) with some fluvial sandstones and minor conglomerates, limestones, and tuffs.

Radiometric U-Pb dates from detrital zircons indicate a latest Albian to early to middle Cenomanian age.

Detrital zircon U-Pb dating within one stratigraphic meter of an Oryctodromeus locality yielded an age of 99.1 +1.5/-1.3 Ma showing proximity to the Albian/Cenomanian stage boundary.

These Oryctodromeus remains exhibit no appreciable pre-burial taphonomic modifications such as weathering, abrasion, breakage, or tooth marks.

[1][2] Excluding eggshell, almost all other vertebrate remains known from the Wayan occur as isolated teeth and partial to complete bones found in high energy fluvial lag and possible debris flow deposits.

Outcrop of the Wayan Formation
An Oryctodromeus family on the Cenomanian floodplains of Idaho. Artwork by L. Krumenacker.
Distal caudal vertebra of Oryctodromeus in-situ in the Wayan Formation. Image used courtesy of the USFS Paleontology Program
Fossil foliage from the Wayan Formation. The ferns Gleichenia (A,B) and Anemaia (C). Conifer foliage (D) and cone (E). Angiosperm leaves (F, G). Notice drip point on F. [ 1 ]
Partial metatarsal from Oryctodromeus recovered from a possible debris flow or fluvial lag in a Wayan Formation outcrop. Image used courtesy of the USFS Paleontology Program