Judith River Formation

The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Montana Group. It dates to the Late Cretaceous, between 79 and 75.3 million years ago,^[4] 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^[5] and the Oldman Formation of Alberta.^[6] 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.

TypeGeological formation

Unit ofMontana Group

Sub-unitsParkman Sandstone Member, McClelland Ferry Member, Coal Ridge Member, Woodhawk Member

UnderliesBearpaw Formation

Quick facts Type, Unit of ...

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	Montana 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)^[1]
Lithology
Primary	Mudstone and sandstone
Location
Region	Alberta, Montana, South Dakota, Saskatchewan, Wyoming
Country	Canada, United States
Type section
Named for	Judith River near the confluence with the Missouri River
Named by	F.V. Hayden, 1871;^[2] F.B. Meek, 1876.^[3]

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Lithology

The Judith River Formation is composed of mudstone, siltstone and sandstone.^[1] 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.^[1] 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.^[7] 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.^[4]

Fauna

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

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.

More information Amphibians of the Judith River Formation, Genus ...

Amphibians of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Habrosaurus	H. dilatus				A siren
Lisserpeton	L. bairdi				A scapherpetonid salamander
Nezpercius^[9]	N. dodsoni	Clambank Hollow			A frog known from a partial illium.
Opisthotriton	O. kayi				A possible lungless salamander
Prodesmodon	P. copei				A lungless salamander
Scapherpeton	S. tectum				A scapherpetonid salamander

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Fish

Bony fish

More information Bony fishes of the Judith River Formation, Genus ...

Bony fishes of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Arotus	A. hieroglyphus				A holostean.^[10]
Belonostomus	Belonostomus longirostris				An aspidorhynchiform.	The holotype of Priscosturion, MOR 1184
Cyclurus	C. fragosus				A bowfin.^[11]
Lepisosteus	L. occidentalis			Scales^[12]	A gar.
?Paralbula	?P. sp.				A bonefish.
Priscosturion	P. longipinnis	McClelland Ferry^[13]	Upper Campanian^[13]		A sturgeon.
Psammorhynchus	P. longipinnis	McClelland Ferry^[13]	Upper Campanian^[13]		Preoccupied name, renamed Priscosturion.^[14]
Polyodontidae	Indeterminate				A paddlefish. Known remains exceeded size of Chinese paddlefish, total length would exceed 2 metres (6.6 ft).^[15]

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Cartilaginous fish

More information Cartilaginous fishes of the Judith River Formation, Genus ...

Cartilaginous fishes of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Myledaphus	M. bipartitus				A stingray.
Cretalamna	C. sp	Montana			An Otodontid shark
Carcharias	Carcharias sp.				A sand tiger shark
Squalicorax	S.kaupi				An Anacoracid shark

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Plesiosaurs

More information Plesiosaurs of the Judith River Formation, Genus ...

Plesiosaurs of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Plesiosauria^[16]	Plesiosauria indet.

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Pterosaurs

More information Pterosaurs of the Judith River Formation, Genus ...

Pterosaurs of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
?Quetzalcoatlus^[17]		Hidden Valley Quarry
Pterosauria	indet	JDM Quarry	McClelland Ferry^[18]			A pterosaur metacarpal from the JDM quarry

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Choristoderes

More information Choristoderes of the Judith River Formation, Genus ...

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

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Crocodilians

More information Crocodilians of the Judith River Formation, Genus ...

Crocodilians of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Brachychampsa	B. montana				An alligatorid.	Brachychampsa
Leidyosuchus	L. canadensis				An alligatoroid.
Deinosuchus	D. hatcheri^[19]			Two giant dorsal vertebrae and a number of osteoderms.	An enormous alligatoroid.	Deinosuchus

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Lizards

More information Lizards of the Judith River Formation, Genus ...

Lizards of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Chamops	C. segnis				A whiptail.
Exostinus	E. lancensis				A knob-scaled lizard.
Leptochamops	L. denticulatus				A whiptail.
Paraderma	P. bogerti				A parasaniwid.
Parasaniwa	P. wyomingensis				A parasaniwid.

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Ornithischians

Ankylosaurs

More information Ankylosaurs reported from the Judith River Formation, Genus ...

Ankylosaurs reported from the Judith River Formation
Genus	Species	Location	Member	Material	Notes	Images
Edmontonia	E. longiceps			Isolated teeth^[20]	A nodosaurid.	Edmontonia
Zuul	Z. crurivastator		middle Coal Ridge	Cranial and postcranial skeletal remains and soft tissue, type specimen	An ankylosaurid.	Zuul

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Hadrosaurs

More information Hadrosaurs reported from the Judith River Formation, Genus ...

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.^[21]	Brachylophosaurus
Corythosaurus	C. sp.^[22]		middle Coal Ridge	two partial skeletons	A lambeosaurine hadrosaurid	Corythosaurus
Probrachylophosaurus	P. bergei		lower McClelland Ferry		A brachylophosaurin hadrosaur	Probrachylophosaurus

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Marginocephalians

Ceratopsians

More information Ceratopsians reported from the Judith River Formation, Genus ...

Ceratopsians reported from the Judith River Formation
Genus	Species	Location	Member	Material	Notes	Images
Albertaceratops	A. nesmoi^[23]				Reclassified as Medusaceratops lokii
Avaceratops	A. lammersi^[23]		lower McClelland Ferry	"[Two] partial skulls, skeleton, juvenile,"^[24] type specimen	A ceratopsid. Possibly dubious.^[25]	Avaceratops
Chasmosaurinae	gen. et sp. nov.			A mostly complete skull	MOR 11940, An unnamed Chasmosaur housed at the Museum of the Rockies.	The skull of the new Chasmosaurine in lateral (side view).
Furcatoceratops	F. elucidans	Fergus County, Montana^[25]	Upper Coal Ridge^[25]	Nearly complete subadult skeleton.^[25]	A ceratopsid	Furcatoceratops
Judiceratops^[26]	J. tigris^[26]		lower McClelland Ferry		A ceratopsid	Judiceratops
Lokiceratops	L. rangiformis^[27]	Kennedy Coulee	lower McClelland Ferry	Disarticulated, associated skeleton including most of the skull and fragmentary postcrania^[27]	A ceratopsid	Lokiceratops
Medusaceratops	M. lokii^[28]		lower McClelland Ferry	Bonebed^[28]	A ceratopsid	Medusaceratops
Mercuriceratops	M. gemini^[29]		lower Coal Ridge	"one apomorphic squamosal"^[29]	A ceratopsid	Mercuriceratops
Spiclypeus	S. shipporum		McClelland Ferry^[30]	Partial skull, vertebrae, ribs, humerus, ilium, femur, tibia, and fibula.	A ceratopsid	Spiclypeus

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Pachycephalosaurs

More information Pachycephalosaurs reported from the Judith River Formation, Genus ...

Pachycephalosaurs reported from the Judith River Formation
Genus	Species	Location	Member	Material	Notes	Images
Colepiocephale	C. lambei^[31]	Kennedy Coulee	lower McClelland Ferry	"nearly complete frontoparietal dome"	A pachycephalosaurid closely related to Stegoceras.	Colepiocephale
Hanssuesia	H. sternbergi				A pachycephalosaurid. Also present in the Dinosaur Park and Oldman Formations. Possible synonym of Stegoceras.	Hanssuesia

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Theropods

Dromaeosaurs

More information Dromeosaurs reported from the Judith River Formation, Genus ...

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.^[32]	lower McClelland Ferry	Teeth^[32]	A dromaeosaurid, also found in the Dinosaur Park Formation	Dromaeosaurus
Saurornitholestes	S. langstoni	Careless Creek, Emily's Ankle, Top Cat, Hidden Valley & Blackbird Ridge quarries.^[32]	Lower McClelland Ferry	Numerous teeth^[32]	A dromaeosaurid	Saurornitholestes

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Troodonts

More information Troodonts reported from the Judith River Formation, Genus ...

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.^[32]		28 teeth^[32]	Teeth of a large theropod distinct from those of tyrannosaurids

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Tyrannosaurs

More information Tyrannosaurs reported from the Judith River Formation, Genus ...

Tyrannosaurs reported from the Judith River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Daspletosaurus	D. torosus		Coal Ridge	Maxilla^[33]	A large tyrannosaurid.	Daspletosaurus
	D. wilsoni^[34]	Jack's B2	lower Coal Ridge^[35]	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 ^[36]^[37]^[38]
	D. sp.		Coal Ridge^[39]	Partial skeleton^[40]^[37]	While initially referred to D. torosus ^[41]^[36], it is more recently classified as Daspletosaurus sp. as it contains some characters in common with other named species of the genus as well as its own unique features. Furthermore, most of the skull is not preserved and is therefore missing many crucial features required for a specific classification ^[35]^[37]
Gorgosaurus	G. libratus			Postorbital^[33]	A large tyrannosaurid, also found in the Dinosaur Park Formation and possibly the Two Medicine Formation.	Gorgosaurus
?Tyrannosaurus	T. sp.	Fergus County		A Lacrimal	Found alongside a specimen of Deinosuchus,^[42] but may not be from the Judith River Formation^[43]

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Other theropods

More information Theropods reported from the Judith River Formation, Genus ...

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.^[44]	Hesperornis
Ornithomimosauria indet.^[45]	Indeterminate		Coal Ridge Member	A left and right dentary	A large ornithomimosaur with potential affinities to the Deinocheiridae	Skull reconstruction of the possible Judith River deinocheirid
Richardoestesia	R. gilmorei	Careless Creek, Emily's Ankle, Hidden Valley & Blackbird Ridge quarries.^[32]		12 teeth^[32]	A coelurosaur

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Dubious Taxa

Many early American dinosaur discoveries were made in the Judith River Formation, and most of the early taxa are considered nomina dubia today.

More information Turtles of the Judith River Formation, Genus ...

Turtles of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Aublysodon	A. lateralis			"Isolated teeth,"^[46]^[47] type specimen	Junior synonym of Deinodon horridus^[8]
Aublysodon	A. mirandus			Teeth, type specimen	Possible junior synonym of Deinodon horridus^[8]
Ceratops	C. montanus			"occipital condyle, paired horn cores,"^[48] type specimen	A dubious ceratopsid
Deinodon	D. falculus			Teeth	Isolated tyrannosaur teeth classified in the dubious genus Deinodon
	D. hazenianus			Teeth	Junior synonym of Deinodon horridus^[8]
	D. horridus			"Teeth,"^[12] type specimen	Isolated tyrannosaur teeth that formed the basis of the dubious genus Deinodon
	D. incrassatus			Teeth	Junior synonym of Deinodon horridus^[8]
	D. lateralis				Junior synonym of Deinodon horridus^[8]
Diclonius	D. calamarius			"Teeth."^[49]	Nomen dubium
	D. pentagonius			"Fragmentary dentary with teeth,"^[49] type specimen	A dubious hadrosaurid
	D. perengulatus			"Teeth."^[49]	Nomen dubium
Dromaeosaurus	D. explanatus			"Tooth."^[50]	Possible relative of Saurornitholestes	Dromaeosaurus
Dromaeosaurus	D. laevifrons			"Tooth."^[50]	Possible relative of Saurornitholestes	Dromaeosaurus
Dysganus	D. bicarinatus			"Isolated teeth."^[48]	Nomen dubium
	D. encaustus			"Single tooth and [five] tooth fragments."^[49] "Isolated teeth."^[48]	Nomen dubium
	D. haydenianus			"Isolated teeth."^[48]	Nomen dubium
	D. peiganus			"Tooth."^[48]	Nomen dubium
~~Hadrosaurus~~	H. paucidens				A dubious hadrosaur, sometimes known as Lambeosaurus paucidens
?"Kritosaurus"	?"K." breviceps				A dubious hadrosaurid
Monoclonius	M. crassus^[23]		lower Coal Ridge	"[Five] skulls, [one] complete."^[24] Type specimen	A dubious ceratopsid
Ornithomimus	O. tenuis			"Fragmentary metatarsal."^[51]	A possible troodontid or juvenile tyrannosaurid
Paleoscincus	P. costatus			"Tooth,"^[12] type specimen	A dubious ankylosaur
Paronychodon	P. lacustris			Teeth, type specimen	An indeterminate maniraptoran, also found in the Dinosaur Park, Milk River, and Kirtland Formations
Pteropelyx	P. grallipes			"Skeleton lacking skull."^[52]	A dubious hadrosaurid
Trachodon	T. mirabilis			Isolated teeth, type specimen^[12]	A dubious hadrosaurid
Troodon	T. formosus	Antelope Head, Careless Creek, Emily's Ankle, Top Cat & Hidden Valley quarries.^[32]		Teeth (type specimen),^[12]^[32] egg	A troodontid, possibly dubious. A neotype from the Two Medicine Formation has been proposed.	Troodon
Zapsalis^[53]	Z. abradens			"Teeth,"^[50] type specimen	A dromaeosaurid

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Turtles

More information Turtles of the Judith River Formation, Genus ...

Turtles of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Adocus^[54]	A. sp.
Aspideretoides^[54]	A. sp
Aspideretoides^[54]	A. foveatus
Axestemys^[54]	A. spledidus
Basilemys^[54]	B. sp.				A Mesoamerican river turtle.
Boremys^[54]	B. sp
Boremys^[54]	B. pulchra
Chelydridae^[54]	indet.
Neuankylus^[54]	N. sp.
Neuankylus^[54]	N. eximius
Plesiobaena^[54]	P. antiqua

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Flora

All the flora stated below is pulled from the PBDB.^[55]^[56]^[57]^[58]

Ferns

More information Ferns of the Judith River Formation, Genus ...

Ferns of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Azollopsis	A. coccoides	Montana
Azolla	A. simplex	Montana
Biretisporites	B. deltoideus	Montana
Baculatisporites	B. sp	Montana
Cyathidites	C. sp	Montana
Deltoidospora	D. diaphana	Montana
Echinatisporis	E. sp	Montana
Laevigatosporites	L. haardtii	Montana
Todisporites	T. dubius	Montana

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Gymnosperms

Cycadophyta

More information Ferns of the Judith River Formation, Genus ...

Ferns of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Cycadopites	C. fragilis	Montana

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Conifers

More information Ferns of the Judith River Formation, Genus ...

Ferns of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Araucariales	Indeterminate	Montana
Pityosporites	P. constrictus	Montana
Taxodiaceaepollenites	T. hiatus	Montana

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Angiosperms

More information Ferns of the Judith River Formation, Genus ...

Ferns of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Scabrastephanocolpites	S. lepidus	Montana
Monosulcites	M. riparius	Montana
Tubulifloridites	T. aedicula	Montana
Erdtmanipollis	E. procumbentiformis	Montana
Liliacidites	L. sp.	Montana

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Judith River Formation

Lithology

Relationship with other units

Sub-divisions

Fauna

Amphibians

Fish

Bony fish

Cartilaginous fish

Plesiosaurs

Pterosaurs

Choristoderes

Crocodilians

Lizards

Ornithischians

Ankylosaurs

Hadrosaurs

Marginocephalians

Ceratopsians

Pachycephalosaurs

Theropods

Dromaeosaurs

Troodonts

Tyrannosaurs

Other theropods

Dubious Taxa

Turtles

Flora

Ferns

Gymnosperms

Cycadophyta

Conifers

Angiosperms

See also

References

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