Wahweap Formation

Wahweap Formation Stratigraphic range: Campanian
Type	Geological formation
Location
Region	North America
Extent	Southern Utah, Northern Arizona
Type section
Named for	Wahweap Creek

The Wahweap Formation of the Grand Staircase-Escalante National Monument is a geological formation in southern Utah and northern Arizona, around the Lake Powell region, whose strata date back to the Late Cretaceous (Campanian stage). Dinosaur remains are among the fossils that have been recovered from the formation.^[1]

Paleobiota

Invertebrates

The Wahweap Formation shows a substantial amount of invertebrate activity ranging from fossilized insect burrows in petrified logs^[2] to various mollusks that characterize the shell beds. Large fossilized crabs are common at most shell bed sites in the Wahweap,^[3] and over 1,900 gastropod specimens (of four likely genera) have been unearthed in the formation's siltstone.^[4]

Fishes

In addition to terrestrial vertebrates, freshwater fish fossils have been uncovered from the Wahweap which include bowfin vertebrae,^[4] ray teeth,^[5] and probable lungfish burrows.^[6]

Dinosaurs

Dinosaurs known from the Wahweap include, at least one type of hadrosaur, at least one or two ceratopsians^[7] and at least one theropod.^[8]

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Basal Dinosauriforms of the Wahweap Formation
Genus	Species	State	Member	Abundance	Notes	Images
Adelolophus[9]	A. hutchisoni				A lambeosaurine hadrosaurid.
Acristavus[10]	A. gagslarsoni				A hadrosaurid closely related to Brachylophosaurus and Maiasaura
Lythronax	L. argestes				A derived tyrannosaurine	Lythronax
Diabloceratops	D. eatoni			Two incomplete skulls	The oldest known centrosaurine dinosaur	Diabloceratops

Mammals

A maniraptoran dinosaur digging a primitive mammal out of its burrow, as per the 2010 discovery by Simpson et al. of trace fossils indicating a predator-prey relationship in the Wahweap Formation.^[11]

A fair number of mammals spanning the lower Campanian are known from the Wahweap as well, including at least 15 genera of multituberculates, cladotherians, marsupials, and placental insectivores.^[12]

Trace fossils

Trace fossils are also relatively abundant in the Wahweap, and include vertebrate tracks as well as burrow activity. Tracks preserved in the capping sandstone indicate the presence of crocodylomorphs, which had been previously known in this area only from teeth elements, as well as ornithischian dinosaurs. At least one possible theropod track has been identified in this area as well.^[13]

In 2010 a unique trace fossil from the Wahweap was discovered that indicates a predator-prey relationship between dinosaurs and primitive mammals. The trace fossil includes at least two fossilized mammalian den complexes as well as associated digging grooves presumably caused by a maniraptoran dinosaur. The proximity indicates a case of probable active predation of the burrow inhabitants by the owners of the claw marks.^[11]

See also

• List of dinosaur-bearing rock formations

References

1. Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. ISBN 0-520-24209-2.
2. De Blieux, Donald D. "Analysis of Jim's hadrosaur site; a dinosaur site in the middle Campanian (Cretaceous) Wahweap Formation of Grand Staircase-Escalante National Monument (GSENM), southern Utah." Abstracts with Programs - Geological Society of America, vol. 39, no. 5, pp.6, May 2007
3. Kirkland, James Ian. "An inventory of paleontological resources in the lower Wahweap Formation (lower Campanian), southern Kaiparowits Plateau, Grand Staircase-Escalante National Monument, Utah." Abstracts with Programs - Geological Society of America, vol.37, no.7, pp.114, Oct 2005.
4. Williams, Jessica A J; Lohrengel, C Frederick. Preliminary study of freshwater gastropods in the Wahweap Formation, Bryce Canyon National Park, Utah. Abstracts with Programs - Geological Society of America, vol. 39, no. 5, pp.43, May 2007
5. Thompson, Cameron R. "A preliminary report on biostratigraphy of Cretaceous freshwater rays, Wahweap Formation and John Henry Member of the Straight Cliffs Formation, southern Utah." Abstracts with Programs - Geological Society of America, vol.36, no.4, pp.91, Apr 2004
6. Orsulak, Megan et al. "A lungfish burrow in late Cretaceous upper capping sandstone member of the Wahweap Formation Cockscomb area, Grand Staircase-Escalante National Monument, Utah." Abstracts with Programs - Geological Society of America, vol. 39, no. 5, pp.43, May 2007
7. http://geology.utah.gov/surveynotes/articles/pdf/horned_dinos_39-3.pdf
8. John Wesley Powell Memorial Museum display, visited April 30th, 2009
9. Gates, Jinnah, Levitt, and Getty, 2014. New hadrosaurid specimens from the lower-middle Campanian Wahweap Formation of southern Utah. pp. 156-173. In The Hadrosaurs: Proceedings of the International Hadrosaur Symposium (D. A. Eberth and D. C. Evans, eds), Indiana University Press, Bloomington.
10. Gates, T.A.; Horner, J.R.; Hanna, R.R.; Nelson, C.R. (2011). "New unadorned hadrosaurine hadrosaurid (Dinosauria, Ornithopoda) from the Campanian of North America". Journal of Vertebrate Paleontology 31 (4): 798–811. doi:10.1080/02724634.2011.577854.
11. http://geology.gsapubs.org/content/38/8/699.abstract
12. Eaton, Jeffrey G; Cifelli, Richard L. "Review of Cretaceous mammalian paleontology; Grand Staircase-Escalante National Monument, Utah. Abstracts with Programs - Geological Society of America, vol.37, no.7, pp.115, Oct 2005
13. Tester, Edward et al. Isolated vertebrate tracks from the Upper Cretaceous capping sandstone member of the Wahweap Formation; Grand Staircase-Escalante National Monument, Utah Abstracts with Programs - Geological Society of America, vol. 39, no. 5, pp.42, May 2007