Judith River Formation

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,^[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.

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)[1]
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;[2] F.B. Meek, 1876.[3]

Lithology

The Judith River Formation is composed of mudstone, siltstone and sandstone.^[1] Coal beds, bentonite and coquinas are also observed.

Judith River Formation, Upper Missouri Breaks National Monument

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

Missouri River carved through the Judith River Formation, Upper Missouri Breaks National Monument

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

Dinosaurs of Judith River Formation

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.

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.
Opisthotriton	O. kayi				A possible lungless salamander.
Prodesmodon	P. copei				A lungless salamander.
Scapherpeton	S. tectum				A scapherpetonid salamander.

Fish

Bony fish

Bony fishes of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Belonostomus	Belonostomus longirostris				An aspidorhynchiform.
Cyclurus	C. fragosus				A bowfin.[9]
Lepisosteus	L. occidentalis			Scales[10]	A gar.
?Paralbula	?P. sp.				A bonefish.
Priscosturion	P. longipinnis	McClelland Ferry[11]	Upper Campanian[11]		A sturgeon.
Psammorhynchus	P. longipinnis	McClelland Ferry[11]	Upper Campanian[11]		Preoccupied name, renamed Priscosturion.[12]
Polyodontidae	Indeterminate				A paddlefish. Known remains exceeded size of Chinese paddlefish, total length would exceed 2 metres (6.6 ft).[13]

Cartilaginous fish

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

Plesiosaurs

Plesiosaurs of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Plesiosauria[14]	Plesiosauria indet.

Pterosaurs

Pterosaurs of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Azhdarchid[15]	Azhdarchidae indet.

Choristoderes

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

Crocodilians

Crocodilians of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Brachychampsa	B. montana				An alligatorid.	Brachychampsa Deinosuchus
Leidyosuchus	L. canadensis				An alligatoroid.
Deinosuchus	D. hatcheri[16]			Two giant dorsal vertebrae and a number of osteoderms.	An enormous alligatoroid.

Lizards

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.

Ornithischians

Ankylosaurs

Ankylosaurs reported from the Judith River Formation
Genus	Species	Location	Member	Material	Notes	Images
Edmontonia	E. longiceps			Isolated teeth[17]	A nodosaurid.	Edmontonia Zuul
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.[18]	Brachylophosaurus Probrachylophosaurus
Corythosaurus	C. sp.[19]		middle Coal Ridge	two partial skeletons	A lambeosaurine hadrosaurid
Diclonius	D. calamarius			"Teeth."[20]	Nomen dubium
	D. pentagonius			"Fragmentary dentary with teeth,"[20] type specimen	A dubious hadrosaurid
	D. perengulatus			"Teeth."[20]	Nomen dubium
Hadrosaurus	H. paucidens				Reclassified as Lambeosaurus? paucidens
?"Kritosaurus"	?"K." breviceps				A dubious hadrosaurid
?Lambeosaurus	?L. paucidens			"Squamosal, maxilla."[20]	Nomen dubium. An indeterminate lambeosaurine.[21]
Paleoscincus	P. costatus			"Tooth,"[10] type specimen	A dubious ankylosaur
Probrachylophosaurus	P. bergei		lower McClelland Ferry		A brachylophosaurin hadrosaur
Pteropelyx	P. grallipes			"Skeleton lacking skull."[22]	A dubious hadrosaurid
Trachodon	T. mirabilis			Isolated teeth, type specimen[10]	A dubious hadrosaurid

Marginocephalians

Ceratopsians

Ceratopsians reported from the Judith River Formation
Genus	Species	Location	Member	Material	Notes	Images
Albertaceratops	A. nesmoi[23]				Reclassified as Medusaceratops lokii	Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus
Avaceratops	A. lammersi[23]		lower McClelland Ferry	"[Two] partial skulls, skeleton, juvenile,"[24] type specimen	A ceratopsid
Ceratops	C. montanus			"occipital condyle, paired horn cores,"[25] type specimen	A dubious ceratopsid
Dysganus	D. bicarinatus			"Isolated teeth."[25]	Nomen dubium
	D. encaustus			"Single tooth and [five] tooth fragments."[20] "Isolated teeth."[25]	Nomen dubium
	D. haydenianus			"Isolated teeth."[25]	Nomen dubium
	D. peiganus			"Tooth."[25]	Nomen dubium
Furcatoceratops	F. elucidans	Fergus County, Montana[26]	Upper Coal Ridge[26]	Nearly complete subadult skeleton.[26]	A ceratopsid
Judiceratops[27]	J. tigris[27]		lower McClelland Ferry		A ceratopsid
Lokiceratops	L. rangiformis[28]	Kennedy Coulee	lower McClelland Ferry	Disarticulated, associated skeleton including most of the skull and fragmentary postcrania[28]	A ceratopsid
Medusaceratops	M. lokii[29]		lower McClelland Ferry	Bonebed[29]	A ceratopsid
Mercuriceratops	M. gemini[30]		lower Coal Ridge	"one apomorphic squamosal"[30]	A ceratopsid
Monoclonius	M. crassus[23]		lower Coal Ridge	"[Five] skulls, [one] complete."[24] Type specimen	A dubious ceratopsid
Spiclypeus	S. shipporum		McClelland Ferry[31]	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[32]	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

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.[33]	lower McClelland Ferry	Teeth[33]	A dromaeosaurid, also found in the Dinosaur Park Formation	Dromaeosaurus Saurornitholestes
	D. explanatus			"Tooth."[34]	Possible relative of Saurornitholestes
	D. laevifrons			"Tooth."[34]	Possible relative of Saurornitholestes
Saurornitholestes	S. langstoni	Careless Creek, Emily's Ankle, Top Cat, Hidden Valley & Blackbird Ridge quarries.[33]	Lower McClelland Ferry	Numerous teeth[33]	A dromaeosaurid
Zapsalis[35]	Z. abradens			"Teeth,"[34] 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.[33]		28 teeth[33]	Teeth of a large theropod distinct from those of tyrannosaurids	Troodon
Troodon	T. formosus	Antelope Head, Careless Creek, Emily's Ankle, Top Cat & Hidden Valley quarries.[33]		Teeth (type specimen),[10][33] 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,"[36][37] type specimen	Junior synonym of Deinodon horridus[8]	Daspletosaurus Gorgosaurus
	A. mirandus			Teeth, type specimen	Possible junior synonym of Deinodon horridus[8]
Daspletosaurus	D. torosus		Coal Ridge	Maxilla[38]	A large tyrannosaurid.
	D. wilsoni[39]	Jack’s B2	lower Coal Ridge[40]	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 [41]
	D. sp.		Coal Ridge[41]	Partial skeleton[42]	Not referrable to D. torosus[40]
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,"[10] 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]
Gorgosaurus	G. libratus			Postorbital[38]	A large tyrannosaurid, also found in the Dinosaur Park Formation and possibly the Two Medicine Formation.
?Tyrannosaurus	T. sp.	Fergus County		A Lacrimal	found alongside a specimen of Deinosuchus,[43] but may not be from the Judith River Formation[44]

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.[45]	Hesperornis
Ornithomimus	O. tenuis			"Fragmentary metatarsal."[46]	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.[33]		12 teeth[33]	A coelurosaur

Turtles

Turtles of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Adocus	A. sp.
Basilemys	B. sp.				A Mesoamerican river turtle.

See also

• List of dinosaur-bearing rock formations