The Williams Fork Formation is a

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

( Edmontonian) geologic formation of the Mesaverde Group in

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

remains are among the fossils that have been recovered from the formation, most notably '' Pentaceratops sternbergii'',. Other fossils found in the formation are the

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

'' Lewyites'',

tyrannosaurids Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to fifteen genera, including the eponymous ''Tyrannosaurus''. The exact number of genera i ...

dromaeosaurids Dromaeosauridae () is a family of feathered coelurosaurian theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Gree ...

troodontids Troodontidae is a clade of bird-like theropod dinosaurs from the Late Jurassic to Late Cretaceous. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinos ...

nodosaurids Nodosauridae is a family of ankylosaurian dinosaurs known from the Late Jurassic to the Late Cretaceous Period (geology), periods in what is now Asia, Europe, North America, and possibly South America. While traditionally regarded as a monophylet ...

ankylosaurids Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. The oldest known ankylosaurids date to around 122 million years ago and went extinct 66 million years ago during the Cretaceous–Pal ...

hadrosaurids Hadrosaurids (), also hadrosaurs or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod fami ...

hybodonts Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like cartilaginous fish (chondrichthyans) which existed from the late Devonian to the Late Cretaceous. Hybodonts share a close common ancestry with modern sharks and Batoide ...

, neosuchian crocodylomorphs, and the mammals '' Glasbius'' and ''

Meniscoessus collomensis ''Meniscoessus'' is a genus of extinct multituberculates from the Upper Cretaceous Period (geology), Period that lived in North America. It is a member of the order (biology), order Multituberculata, belonging to the suborder Cimolodonta and fa ...

''.Rangely South (SDNHM)
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Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

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References

Bibliography

* * Diem, Stephen Daniel. (1999). Vertebrate Faunal Analysis of the Upper Cretaceous Williams Fork Formation, Rio Blanco County, Colorado aster’s Thesis San Diego State University.

* Archibald, J. D. (1987). Late Cretaceous (Judithian and Edmontonian) Vertebrates and Geology of the Williams Fork Formation. N.W. Colorado. In P. J. Currie, E. H. Koster, & Royal Tyrrell Museum of Palaeontology (Eds.), Fourth Symposium on Mesozoic Terrestrial Ecosystems: Drumheller, August 10–14, 1987: Short Papers (Rev. ed, pp. 7–11). Tyrrell Museum of Palaeontology. * Brand, N., Heckert, A., Sanchez, I., Foster, J., Hunt-Foster, R., & Eberle, J. (2022). New Upper Cretaceous Microvertebrate Assemblage from the Williams Fork Formation, northwestern Colorado, U.S.A., and its Paleoenvironmental Implications. Acta Palaeontologica Polonica, 67(3), 579–600. https://doi.org/10.4202/app.00934.2021. * Cifelli, R. L., Eberle, J. J., Lofgren, D. L., Lillegraven, J. A., & Clemens, W. A. (2004). Mammalian Biochronology of the Latest Cretaceous. In M. O. Woodburne (Ed.), Late Cretaceous and Cenozoic Mammals of North America: Biostratigraphy and Geochronology (pp. 21–42). Columbia University Press. https://www.jstor.org/stable/10.7312/wood13040.8. * Diem, Stephen Daniel. (1999). Vertebrate Faunal Analysis of the Upper Cretaceous Williams Fork Formation, Rio Blanco County, Colorado aster’s Thesis San Diego State University. * Noll, M. D. (1998). Sedimentology of the Upper Cretaceous Williams Fork Formation, Rio Blanco County, Northwestern Colorado aster’s Thesis San Diego State University. https://digitallibrary.sdsu.edu/islandora/object/sdsu%3A17 * J. R. Foster and R. K. Hunt-Foster. 2015. First report of a giant neosuchian (Crocodyliformes) in the Williams Fork Formation (Upper Cretaceous: Campanian) of Colorado. Cretaceous Research 55:66-73 * Lockley, M. G., Smith, J. A., & King, M. R. (2018). First reports of turtle tracks from the Williams Fork Formation (‘Mesaverde’ Group), Upper Cretaceous (Campanian) of western Colorado. Cretaceous Research, 84, 474–482. https://doi.org/10.1016/j.cretres.2017.11.001. * W. J. Kennedy, W. A. Cobban, and G. R. Scott. 2000. Heteromorph ammonites from the Upper Campanian (Upper Cretaceous) ''Baculites cuneatus'' and ''Baculites reesidei'' zones of the Pierre Shale in Colorado, USA. Acta Geologica Polonica 50:1-20 * J. A. Lillegraven. 1987. Stratigraphic and evolutionary implications of a new species of ''Meniscoessus'' (Multituberculata, Mammalia) from the Upper Cretaceous Williams Fork Formation, Moffat County, Colorado. Dakoterra 3:46-56 * Sullivan, R.M., and Lucas, S.G. 2006.
The Kirtlandian land-vertebrate "age" – faunal composition, temporal position and biostratigraphic correlation in the nonmarine Upper Cretaceous of western North America
" New Mexico Museum of Natural History and Science, Bulletin 35:7-29. {{Chronostratigraphy of Colorado, Mesozoic state=expanded Geologic formations of Colorado Cretaceous Colorado Campanian Stage Mudstone formations of the United States Sandstone formations of the United States Fluvial deposits Shallow marine deposits

See also

References

Bibliography

Further reading