Willow Tank Formation

Willow Tank Formation
Willow Tank Formation
Stratigraphic range: Late Cretaceous, Cenomanian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Underlies	Baseline Sandstone
Overlies	Aztec Sandstone
Thickness	unknown
Lithology
Primary	Claystone, conglomerate, sandstone
Location
Coordinates	36°27′22″N 114°31′59″W / 36.45611°N 114.53306°W
Approximate paleocoordinates	20°48′N 53°24′W / 20.8°N 53.4°W
Region	Nevada
Country	United States
Extent	Valley of Fire, Nevada

The Willow Tank Formation is a geologic formation which outcrops in the U.S. state of Nevada. Initially believed to be of Early Cretaceous (Albian) age, later studies have concluded that it was more likely to be of Late Cretaceous (Cenomanian) age, making it equivalent to the Wayan Formation and the Mussentuchit Member of the Cedar Mountain Formation. It was deposited in an anastomosed fluvial system.

Fossil records

The list is primarily based on Bonde (2008) and Bonde et al. (2008), unless stated otherwise.

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.

Plants

Plants of the Willow Tank Formation
Genus	Species	Presence	Materials	Notes	Images
Cladophlebis	C. sp.
Matonia	M. sp.

Gastropods

Gastropods of the Willow Tank Formation
Genus	Species	Presence	Materials	Notes	Images
Gastropoda	indeterminate		Single shell

Fish

Fishes of the Willow Tank Formation
Genus	Species	Presence	Materials	Notes	Images
Ceratodus	C. sp.		Teeth plates
Lepisosteidae	indeterminate		Ganoid scales, rectangular to rhoombohedral in shape
Holostean	indeterminate		Ganoid scales, polygonal in shape

Testudines

Turtles of the Willow Tank Formation
Genus	Species	Presence	Materials	Notes	Images
Naomichelys	N. speciosa		Carapace and plastron elements
Baenidae	indeterminate		Shell elements and a pelvic girdle
cf. Adocus	cf. A. sp.		Several shell specimens
?Trionychidae	indeterminate		Fragmentary specimens

Crocodylomorphs

Crocodylomorphs of the Willow Tank Formation
Genus	Species	Presence	Materials	Notes	Images
Crocodylomorpha	indeterminate		Dental elements and scutes

Dinosaurs

Dinosaurs of the Willow Tank Formation
Genus	Species	Presence	Materials	Notes	Images
Theropoda	indeterminate		Dental elements, and two different eggshell morphotypes	One of the eggshell morphotype shows similarities with Macroelongatoolithus carylei
Tyrannosauroidea	indeterminate		Dental elements
Dromaeosauridae	indeterminate		Femur, tibia and teeth
Titanosauriformes	indeterminate		Single tooth
Nevadadromeus	N. schmitti		Partial skeleton
Iguanodontia	indeterminate		Teeth and partial skeleton	Includes Iguanodon-grade taxa and hadrosaur-grade taxa according to Bonde (2008).
Thyreophora	indeterminate		Dental remains

References

↑ Longwell, C.R. (1949). "Structure of the Northern Muddy Mountain Area, Nevada". Geological Society of America Bulletin. 60 (5): 923–968. Bibcode:1949GSAB...60..923L. doi:10.1130/0016-7606(1949)60[923:sotnmm]2.0.co;2. Wikidata Q60182382.
1 2 3 Bonde, Joshua (December 19, 2008). PALEOECOLOGY AND TAPHONOMY OF THE WILLOW TANK FORMATION (ALBIAN), SOUTHERN NEVADA (Unpublished Master's thesis). Montana State University.
↑ "Lake Mead G-E-M resources area (GRA no. NV-35) : Technical report (WSAs NV 050-0231, 050–0233, 050–0235, 050–0236, and 050-0238) : Final report" (PDF).
↑ "Nellis/Quail Spring G-E-M resources area (GRA no. NV-33) : Technical report (WSAs NV 050-0411, 050-04R-15A, B, and C) : Final report" (PDF).
↑ "Muddy Mountains G-E-M resources area (GRA no. NV-34) : Technical report (WSA NV 050-0229) : Final report" (PDF).
↑ Bonde, Joshua W.; Varricchio, David J.; Jackson, Frankie D.; Loope, David B.; Shirk, Aubrey M. (2008). "Dinosaurs and dunes! Sedimentology and paleontology of the Mesozoic in the Valley of Fire State Park". GSA Field Guide 11: Field Guide to Plutons, Volcanoes, Faults, Reefs, Dinosaurs, and Possible Glaciation in Selected Areas of Arizona, California, and Nevada. 11: 249–262. doi:10.1130/2008.fld011(11). Retrieved October 1, 2026.
↑ Bonde, Joshua W.; Hall, Rebecca L.; Krumenacker, L. J.; Varricchio, David J. (October 14, 2022). "Nevadadromeus schmitti (gen. et sp. nov.), a New Basal Neornithischian with Affinities to the Thescelosaurinae, from the Upper Cretaceous (Cenomanian) Willow Tank Formation of Southern Nevada". Journal of the Arizona-Nevada Academy of Science. 50 (1). doi:10.2181/036.050.0101.

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[Longwell1949-1] Longwell, C.R. (1949). "Structure of the Northern Muddy Mountain Area, Nevada". Geological Society of America Bulletin. 60 (5): 923–968. Bibcode:1949GSAB...60..923L. doi:10.1130/0016-7606(1949)60[923:sotnmm]2.0.co;2. Wikidata Q60182382.

[B8-2] 1 2 3 Bonde, Joshua (December 19, 2008). PALEOECOLOGY AND TAPHONOMY OF THE WILLOW TANK FORMATION (ALBIAN), SOUTHERN NEVADA (Unpublished Master's thesis). Montana State University.

[3] "Lake Mead G-E-M resources area (GRA no. NV-35) : Technical report (WSAs NV 050-0231, 050–0233, 050–0235, 050–0236, and 050-0238) : Final report" (PDF).

[4] "Nellis/Quail Spring G-E-M resources area (GRA no. NV-33) : Technical report (WSAs NV 050-0411, 050-04R-15A, B, and C) : Final report" (PDF).

[5] "Muddy Mountains G-E-M resources area (GRA no. NV-34) : Technical report (WSA NV 050-0229) : Final report" (PDF).

[BVJLS08-6] Bonde, Joshua W.; Varricchio, David J.; Jackson, Frankie D.; Loope, David B.; Shirk, Aubrey M. (2008). "Dinosaurs and dunes! Sedimentology and paleontology of the Mesozoic in the Valley of Fire State Park". GSA Field Guide 11: Field Guide to Plutons, Volcanoes, Faults, Reefs, Dinosaurs, and Possible Glaciation in Selected Areas of Arizona, California, and Nevada. 11: 249–262. doi:10.1130/2008.fld011(11). Retrieved October 1, 2026.

[BHKV22-7] Bonde, Joshua W.; Hall, Rebecca L.; Krumenacker, L. J.; Varricchio, David J. (October 14, 2022). "Nevadadromeus schmitti (gen. et sp. nov.), a New Basal Neornithischian with Affinities to the Thescelosaurinae, from the Upper Cretaceous (Cenomanian) Willow Tank Formation of Southern Nevada". Journal of the Arizona-Nevada Academy of Science. 50 (1). doi:10.2181/036.050.0101.