Wayan Formation
Encyclopedia
The Wayan Formation is a geological formation in Idaho whose strata date back to the earliest Late Cretaceous
. Dinosaur remains are among the fossils that have been recovered from the formation.
age.
The Wayan is equivalent to the upper Cedar Mountain Formation
of Utah, the Aspen Shale of Wyoming, and the Blackleaf Formation of Montana.
, which is known from several partial skeletons. Ankylosaurs, Tenontosaurus
-like iguanodontids, large theropods, dromaeosaurs, possible neoceratopsians, large and small crocodilians, turtles, and semionotid fish are known from very fragmentary remains. Dinosaur eggshell of the family Elongatoolithidae is one of the more common fossils found.
Fossil plants are rare, but petrified wood, and foliage from angiosperms, conifers and ferns has been reported
.
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
. Dinosaur remains are among the fossils that have been recovered from the formation.
Geology and Age
The Wayan occurs in eastern Idaho. Sediments are dominantly floodplain mudstones (some pedogenic) with some fluvial sandstones and minor conglomerates, limestones, and tuffs. Carbonate nodules in pedogenic mudstones suggest a semi-arid, seasonal climate during deposition. Radiometric U-Pb dates from detrital zircons indicate an early to middle CenomanianCenomanian
The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...
age.
The Wayan is equivalent to the upper Cedar Mountain Formation
Cedar Mountain Formation
The Cedar Mountain Formation is the name given to distinctive sedimentary rocks in eastern Utah that occur between the underlying Morrison Formation and overlying Naturita Formation . It is composed of non-marine sediments, that is, sediments deposited in rivers, lakes and on flood plains...
of Utah, the Aspen Shale of Wyoming, and the Blackleaf Formation of Montana.
Fauna and Flora
The vertebrate fauna is dominated by the small basal ornithopod OryctodromeusOryctodromeus
Oryctodromeus was a genus of small ornithopod dinosaur. Fossils are known from the middle Cretaceous Blackleaf Formation of southwestern Montana and the Wayan Formation of southeastern Idaho, both of the Cenomanian stage, roughly 95 million years ago...
, which is known from several partial skeletons. Ankylosaurs, Tenontosaurus
Tenontosaurus
Tenontosaurus is a genus of medium- to large-sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceous period sediments of western North America, dating between 115 to 108 million years ago...
-like iguanodontids, large theropods, dromaeosaurs, possible neoceratopsians, large and small crocodilians, turtles, and semionotid fish are known from very fragmentary remains. Dinosaur eggshell of the family Elongatoolithidae is one of the more common fossils found.
Fossil plants are rare, but petrified wood, and foliage from angiosperms, conifers and ferns has been reported
.
Vertebrate Fauna
- Cf. Semionotidae
- Chelonia.
- Crocodylia
- OryctodromeusOryctodromeusOryctodromeus was a genus of small ornithopod dinosaur. Fossils are known from the middle Cretaceous Blackleaf Formation of southwestern Montana and the Wayan Formation of southeastern Idaho, both of the Cenomanian stage, roughly 95 million years ago...
sp. - Indeterminate TenontosaurusTenontosaurusTenontosaurus is a genus of medium- to large-sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceous period sediments of western North America, dating between 115 to 108 million years ago...
-like iguanodontids sp. - Ornithopoda indet.
- ?NodosauridaeNodosauridaeNodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous Period of what are now North America, Asia, Antarctica and Europe.-Characteristics:...
indet. - Neoceratopsia indet.
- DromaeosauridaeDromaeosauridaeDromaeosauridae is a family of bird-like theropod dinosaurs. They were small- to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'...
indet.
- Dinosaur eggshell referrable to the oofamily Elongatoolithidae
Macroflora
- GleicheniaGleicheniaGleichenia is a genus of ferns.Species include:* Gleichenia abscida Rodway* Gleichenia alpina R.Br.* Gleichenia dicarpa R.Br. – Pouched Coral Fern, Tangle Fern* Gleichenia mendellii S.B.Andrews...
- Anemia
- Angiospermae unidet.
- Coniferae unidet.