Wahweap Formation

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.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. .

Age The Wahweap formation is divided into four members, which are listed below with their respective ages:

Last Chance Creek Member: 82.17-81.55 Ma Reynolds Point Member: 81.55-80.61 Ma Coyote Point Member: 80.61-79 Ma Pardner Canyon Member: 79-77.29 Ma

Paleobiota

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

Elasmobranchs +Elasmobranchs of the Wahweap FormationTaxonSpeciesLocalityMemberMaterialNotesImagesCantioscylliumC. estesi MNA Locality 705 MNA Locality 455-1 UMNH VP Locality 82MNA V10230-32, MNA V10384-85, MNA 10390, UMNH VP 18915-16, UMNH VP 18919; teethA nurse shark which inhabited freshwater.ChiloscylliumC. missouriense UMNH VP Locality 77 MNA Locality 455-1MNA V10386, UMNH VP 18880, UMNH VP 18882, UMMNH VP 18886, UMNH VP 18887, UMNH VP 18888; teethA bamboo shark which inhabited freshwater. One specimen is similar to Restesia americana.ColumbusiaC. deblieuxiUMNH VP Locality 77UMNH VP 18877, UMNH VP 18879, UMNH VP 18836, UMNH VP 18876, UMNH VP 18878; teethA sclerorhynchid ray, closely related to Squatirhina.CristomylusC. ciffelli MNA Locality 456-1 UMNH VP Locality 77 UMNH VP Locality 82 MNA V9531, MNA V9568, MNA V9600, UMNH VP 17393; symphysial teeth MNA V9502, MNA V9525, MNA V9569, MNA V9633, MNA V9635, MNA V9652, UMNH VP 17393, UMNH VP 17395, UMNH VP 17399, UMNH VP 17404; small teeth MNA V9593, MNA V9683, MNA V9686, UMNH VP 17401; large teethA small guitarfish, suited for handling hard-shelled prey.Hybodus?H. spMNA Locality 456-2MNA V10387; ToothA large hybodont shark reaching over in length. Normally a marine species but would enter freshwater environmentsLonchidionL. sp.UMNH VP Locality 82UMNH VP 18917; ToothSmaller than Lonchidon selachos.TexatrygonT. brycensis UMNH VP Locality 77 UMNH VP Locality 82 UMNH VP 18882-83; Rostral teeth UMNH VP 18836, UMNH VP 18885, UMNH VP 18889-94, UMNH VP 18920; Oral teeth UMNH VP 18918; denticleA sawfish.

Osteichthyes +Osteichthyes of the Wahweap FormationTaxonGenusLocalityMemberMaterialNotesImagesLepidotesIndeterminateTeethA seminotiform fish, no extant relatives live today.MicropycnodonM. sp.MNA Locality 706-2MNA V10336; pharyngeal toothA pycnodontiform fish, adapted to crush its prey.ParalbulaP. sp.TeethA bonefish which is adapted to eating hard-shelled prey.PolyodontidaeIndeterminateMNA Locality 456-2MNA 10356; denticleA paddlefish, very rare in the Wahweap Formation.

Salamanders +Lissamphibians of the Wahweap FormationTaxonSpeciesLocalityMemberMaterialNotesImagesGen. nov.sp. nov.UMNH VP Locality 77UMNH VP 19209; trunk vertebraHigher level relationships are uncertain. Similar to sirenids, but lacks sirenid synapomorphies.OpisthotritonO. sp.UMNH VP Locality 130 UMNH VP 19194-19198; atlantes UMNH VP 19199-19200; trunk vertebraeA batrachosauroidid, a family of extinct aquatic salamanders.ScapherpetonS. sp.UMNH VP Locality 77UMNH VP 19186; atlasA scapherpetontid.

Dinosaurs

Dinosaurs known from the Wahweap include at least 2 species of hadrosaur, at least two ceratopsians and at least one theropod.John Wesley Powell Memorial Museum display, visited April 30, 2009 Dinosaurs of the Wahweap Formation Taxon SpeciesLocality Member Material Notes ImagesAcristavus A. gagslarsoni"near the junction of Smokey Mountain Road and Right Hand Collet Canyon"Upper part of Reynolds Point MemberUMNH VP 16607; "a partial articulated skull roof including lacrimals and entire braincase, and a single cervical vertebra"A hadrosaurid closely related to Brachylophosaurus and Maiasaura. Also known from the Two Medicine Formation.AdelolophusA. hutchisoniUCMP V98173Lower part of Coyote Point MemberUCMP 152028; partial A lambeosaurine hadrosaurid, possibly a parasaurolophin.AnkylosauridaeIndeterminateCoyote Point MemberOMNH 21280 (in part), OMNH 21858, OMNH 24276; TeethBrachylophosaurusIndeterminateDeath RidgeUpper part of Coyote Point MemberUMNH VP 9548; "Partial limb bones and a partial maxilla"Different from Acristavus.CentrosaurinaeIndeterminateNipple ButteUpper part of Last Chance Creek MemberUMNH VP 16704; Partial skullOriginally referred to Diabloceratops, but is more derived, possibly a nasutoceratopsin.CentrosaurinaeIndeterminatePilot KnollUpper part of Last Chance Creek MemberUMNH VP 20600; "A partial braincase and a nearly complete parietosquamosal frill"Also known as "Wahweap Centrosaurine A." Similar to Albertaceratops.CentrosaurinaeIndeterminateDeath RidgeUpper part of Coyote Point MemberUMNH VP 9549; "Partial frill and some postcranial elements"Also known as "Wahweap Centrosaurine C." Possibly has spikes similar to Styracosaurus.DiabloceratopsD. eatoni42Ka800V, south side of Last Chance CanyonMiddle part of Reynolds Point MemberUMNH VP 166999; "a skull preserving the entire left side of the skull and portions of the right side"The older specimen from Nipple Butte may not belong to Diabloceratops.LythronaxL. argestesUMNH VP Locality 1501Lower part of Reynolds Point MemberUMNH VP 20200; partial skeletonA tyrannosaurineMachairoceratopsM. cronusiStar SeepCoyote Point MemberUMNH VP 20550; partial skull A centrosaurine closely related to Diabloceratops. Previously known as "Wahweap Centrosaurine B."NodosauridaeIndeterminate Last Chance Creek Member? Reynolds Point Member Coyote Point Member OMNH 21280 (in part), OMNH 21992, OMNH 24278; Teeth UMNH VP 13981, UMNH VP 15664, UMNH VP 16408, UMNH VP 21207; osteoderms a cranium (lost) a partial skeletonThe skeleton was under excavation as of 2013. The cranium was only tentatively identified as a nodosaurid, but now can't be confirmed.PachycephalosauridaeIndeterminateClints CoveLower part of Reynolds Point Member UMNH VP 11939; incomplete frontoparietal dome some isolated teethThe dome doesn't preserve diagnostic features, so its affinity with other pachycephalosaurids is uncertain.SaurolophinaeIndeterminateReynolds Point Member UMNH VP 21087; partial juvenile skeleton UMNH VP 13881; partial adult skeletonProbably represents a new distinct taxon.

Mammals

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.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

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.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

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.

Wahweap Formation

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