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Judith River Formation
Stratigraphic range: Campanian, 79–75.3 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Judith River Formation, Upper Missouri Breaks National Monument
Type	Geological formation
Unit of	Judith River Group
Sub-units	Parkman Sandstone Member, McClelland Ferry Member, Coal Ridge Member, Woodhawk Member
Underlies	Bearpaw Formation
Overlies	Claggett Formation, Pakowki Formation
Thickness	max 360 meters (1,180 ft)
Lithology
Primary	Mudstone and sandstone
Location
Region	Montana
Country	United States
Type section
Named for	Judith River near the confluence with the Missouri River
Named by	F.V. Hayden, 1871; F.B. Meek, 1876.

The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the Late Cretaceous, between 79 and 75.3 million years ago, corresponding to the "Judithian" land vertebrate age. It was laid down during the same time period as portions of the Two Medicine Formation of Montana and the Oldman Formation of Alberta. It is an historically important formation, explored by early American paleontologists such as Edward Drinker Cope, who named several dinosaurs from scrappy remains found here on his 1876 expedition (such as Monoclonius). Modern work has found nearly complete skeletons of the hadrosaurid Brachylophosaurus.

Lithology

The Judith River Formation is composed of mudstone, siltstone and sandstone. Coal beds, bentonite and coquinas are also observed.

Relationship with other units

The Judith River Formation conformably overlies the Claggett Formation and Pakowki Formation. It is overlain by the Bearpaw Formation. It is equivalent to the Belly River Formation in the southern Canadian Rockies foothills, the Lea Park Formation in central Alberta and the Wapiti Formation in the northwestern plains.

Sub-divisions

The Judith River Formation is divided into four members, the Parkman Sandstone Member, the McClelland Ferry Member, the Coal Ridge member, and the Woodhawk Member. The McClelland Ferry Member (78.7-76.3 Ma) is believed to be equivalent to the Oldman Formation, with the Coal Ridge Member (76.3-75.3 Ma) equivalent to the Dinosaur Park Formation.

Fauna

Faunal list follows a review published by Ashok Sahni in 1972 unless otherwise noted.

Amphibians

There are three potential species of discoglossid frogs. Hip bones, possibly representing a North American member of the European spadefoot toad family are also known from the formation.

Fish

Bony fish

Cartilaginous fish

Choristoderes

Choristoderes of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Champsosaurus	C. sp.

Crocodilians

Crocodilians of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Brachychampsa	B. montana				An alligatorid.
Leidyosuchus	L. canadensis				An alligatoroid.
Deinosuchus	D. hatcheri			Two giant dorsal vertebrae and a number of osteoderms.	An enormous alligatoroid.

Lizards

Ornithischians

Ankylosaurs

Ankylosaurs reported from the Judith River Formation
Genus	Species	Location	Member	Material	Notes	Images
Edmontonia	E. longiceps			Isolated teeth	A nodosaurid.
Zuul	Z. crurivastator		middle Coal Ridge	Cranial and postcranial skeletal remains and soft tissue, type specimen	An ankylosaurid

Hadrosaurs

Hadrosaurs reported from the Judith River Formation
Genus	Species	Location	Member	Material	Notes	Images
Brachylophosaurus	B. canadensis		middle McClelland Ferry		A hadrosaurid which was one of the more common dinosaurs in the area.
Corythosaurus	C. sp.		middle Coal Ridge	two partial skeletons	A lambeosaurine hadrosaurid
Diclonius	D. calamarius			"Teeth."	Nomen dubium
	D. pentagonius			"Fragmentary dentary with teeth," type specimen	A dubious hadrosaurid
	D. perengulatus			"Teeth."	Nomen dubium
Hadrosaurus	H. paucidens				Reclassified as Lambeosaurus? paucidens
?"Kritosaurus"	?"K." breviceps				A dubious hadrosaurid
?Lambeosaurus	?L. paucidens			"Squamosal, maxilla."	Nomen dubium. An indeterminate lambeosaurine.
Paleoscincus	P. costatus			"Tooth," type specimen	A dubious ankylosaur
Probrachylophosaurus	P. bergei		lower McClelland Ferry		A brachylophosaurin hadrosaur
Pteropelyx	P. grallipes			"Skeleton lacking skull."	A dubious hadrosaurid
Trachodon	T. mirabilis			Isolated teeth, type specimen	A dubious hadrosaurid

Marginocephalians

Ceratopsians

Ceratopsians reported from the Judith River Formation
Genus	Species	Location	Member	Material	Notes	Images
Albertaceratops	A. nesmoi				Reclassified as Medusaceratops lokii
Avaceratops	A. lammersi		lower McClelland Ferry	" partial skulls, skeleton, juvenile," type specimen	A ceratopsid
Ceratops	C. montanus			"occipital condyle, paired horn cores," type specimen	A dubious ceratopsid
Dysganus	D. bicarinatus			"Isolated teeth."	Nomen dubium
	D. encaustus			"Single tooth and tooth fragments." "Isolated teeth."	Nomen dubium
	D. haydenianus			"Isolated teeth."	Nomen dubium
	D. peiganus			"Tooth."	Nomen dubium
Furcatoceratops	F. elucidans	Fergus County, Montana	Upper Coal Ridge	Nearly complete subadult skeleton.	A ceratopsid
Judiceratops	J. tigris		lower McClelland Ferry		A ceratopsid
Lokiceratops	L. rangiformis	Kennedy Coulee	lower McClelland Ferry	Disarticulated, associated skeleton including most of the skull and fragmentary postcrania	A ceratopsid
Medusaceratops	M. lokii		lower McClelland Ferry	Bonebed	A ceratopsid
Mercuriceratops	M. gemini		lower Coal Ridge	"one apomorphic squamosal"	A ceratopsid
Monoclonius	M. crassus		lower Coal Ridge	" skulls, complete." Type specimen	A dubious ceratopsid
Spiclypeus	S. shipporum		McClelland Ferry	Partial skull, vertebrae, ribs, humerus, ilium, femur, tibia, and fibula.	A ceratopsid

Pachycephalosaurs

Pachycephalosaurs reported from the Judith River Formation
Genus	Species	Location	Member	Material	Notes	Images
Colepiocephale	C. lambei	Kennedy Coulee	lower McClelland Ferry	"nearly complete frontoparietal dome"	A pachycephalosaurid closely related to Stegoceras.
Hanssuesia	H. sternbergi				A pachycephalosaurid. Also present in the Dinosaur Park and Oldman Formations. Possible synonym of Stegoceras.

Theropods

Dromaeosaurs

Dromeosaurs reported from the Judith River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Dromaeosaurus	D. albertensis	Ox Hill Quarry, Careless Creek Quarry, Hidden Valley Quarry & Blackbird Ridge Quarry.	lower McClelland Ferry	Teeth	A dromaeosaurid, also found in the Dinosaur Park Formation
	D. explanatus			"Tooth."	Possible relative of Saurornitholestes
	D. laevifrons			"Tooth."	Possible relative of Saurornitholestes
Saurornitholestes	S. langstoni	Careless Creek, Emily's Ankle, Top Cat, Hidden Valley & Blackbird Ridge quarries.	Lower McClelland Ferry	Numerous teeth	A dromaeosaurid
Zapsalis	Z. abradens			"Teeth," type specimen	A dromaeosaurid

Troodonts

Troodonts reported from the Judith River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Theropod "A"		Antelope Head, Careless Creek, Emily's Ankle, Top Cat, Hidden Valley, Blackbird Ridge & Jensen Ranch quarries.		28 teeth	Teeth of a large theropod distinct from those of tyrannosaurids
Troodon	T. formosus	Antelope Head, Careless Creek, Emily's Ankle, Top Cat & Hidden Valley quarries.		Teeth (type specimen), egg	A troodontid, possibly dubious.

Tyrannosaurs

Tyrannosaurs reported from the Judith River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Aublysodon	A. lateralis			"Isolated teeth," type specimen	Junior synonym of Deinodon horridus
	A. mirandus			Teeth, type specimen	Possible junior synonym of Deinodon horridus
Daspletosaurus	D. torosus		Coal Ridge	Maxilla and a partial skeleton	A large tyrannosaurid.
	D. wilsoni	Jack’s B2	lower Coal Ridge	Partial skull, cervical, sacral, and caudal vertebrae, and a rib, chevron, and first metatarsal	Originally considered to be a transitional species between D. torosus and D. horneri, though the validity of this claim has been questioned
	D. sp.		Coal Ridge	Partial skeleton	Not referrable to D. torosus
Deinodon	D. falculus			Teeth	Isolated tyrannosaur teeth classified in the dubious genus Deinodon
	D. hazenianus			Teeth	Junior synonym of Deinodon horridus
	D. horridus			"Teeth," type specimen	Isolated tyrannosaur teeth that formed the basis of the dubious genus Deinodon
	D. incrassatus			Teeth	Junior synonym of Deinodon horridus
	D. lateralis				Junior synonym of Deinodon horridus
Gorgosaurus	G. libratus			Postorbital	A large tyrannosaurid, also found in the Dinosaur Park Formation and possibly the Two Medicine Formation.

Other Theropods

Theropods reported from the Judith River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Hesperornis	H. altus			Partial tibiotarsus	One of the only known freshwater occurrences of a hesperornithid.
Ornithomimus	O. tenuis			"Fragmentary metatarsal."	A possible troodontid or juvenile tyrannosaurid
Paronychodon	P. lacustris			Teeth, type specimen	An indeterminate maniraptoran, also found in the Dinosaur Park, Milk River, and Kirtland Formations
Richardoestesia	R. gilmorei	Careless Creek, Emily's Ankle, Hidden Valley & Blackbird Ridge quarries.		12 teeth	A coelurosaur

Turtles

See also

• List of dinosaur-bearing rock formations

References

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2. Hayden, F.V., 1871. Geology of the Missouri Valley: Preliminary report (4th annual) of the Geol. Surv. of Wyoming and portions of contiguous territories.
3. Meek, Fielding Bradford, 1876. A report on the invertebrate Cretaceous and Tertiary fossils of the upper Missouri country, Hayden, F.V., Geologist in Charge; United States Geologic and Geographic Survey of the Territories, vol. 9, page 629
4. ^ Ramezani, Jahandar; Beveridge, Tegan L.; Rogers, Raymond R.; Eberth, David A.; Roberts, Eric M. (2022-09-26). "Calibrating the zenith of dinosaur diversity in the Campanian of the Western Interior Basin by CA-ID-TIMS U–Pb geochronology". Scientific Reports. 12 (1): 16026. doi:10.1038/s41598-022-19896-w. ISSN 2045-2322. PMC 9512893. PMID 36163377.
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• Campanian Stage
• Cretaceous Montana
• Cretaceous geology of South Dakota
• Stratigraphy of Alberta