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 80 and 75 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[1] and the Oldman Formation of Alberta.[5] 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, 79–74.9 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓ [1]
"Leonardo," a rare intact mummified Brachylophosaurus canadensis uncovered in the Judith River Formation.
Type	Geological formation
Unit of	Judith River Group
Sub-units	Birch Lake Member, Ribstone Creek Member, Brosseau Member, Victoria Member
Underlies	Bearpaw Formation
Overlies	Claggett Formation, Pakowki Formation
Thickness	max 360 meters (1,180 ft)[2]
Lithology
Primary	Siltstone and sandstone
Other	Coal, coquinas
Location
Coordinates	47°40′N 109°39′W
Region	Montana
Country	United States
Type section
Named for	Confluence of Judith River and Missouri River
Named by	F.V. Hayden, 1871;[3] F.B. Meek, 1876.[4]

Lithology

The Judith River Formation is composed of mudstone, siltstone and sandstone.[2] 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.[2] 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 Birch Lake Member and Ribstone Creek Member are sandstone units recognized inside the Judith River Formation. Other informal subdivisions include the Brosseau Member and Victoria Member, which are considered obsolete due to their inconsistent lateral distribution.

Fauna

Faunal list follows a review published by Ashok Sahni in 1972 unless otherwise noted.[6]

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.

Bony fish

Bony fishes of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Belonostomus	Belonostomus longirostris				An aspidorhynchiform.
Kindleia	K. fragosa				A bowfin.
Lepisosteus	L. occidentalis				A gar.
?Paralbula	?P. sp.				A bonefish.

Cartilaginous fish

Cartilaginous fishes of the Judith River Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Myledaphus	M. bipartitus				A stingray.

Ornithischian dinosaurs

Ornithischians reported from the Judith River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Albertaceratops	A. nesmoi[7]				Reclassified as Medusaceratops lokii	Avaceratops Brachylophosaurus Judiceratops Medusaceratops Mercuriceratops Monoclonius Probrachylophosaurus Spiclypeus Zuul
Avaceratops	A. lammersi[7]			"[Two] partial skulls, skeleton, juvenile,"[8] type specimen	A ceratopsid
Brachylophosaurus	B. canadensis				A hadrosaurid
Ceratops	C. montanus			"occipital condyle, paired horn cores,"[9] type specimen	A dubious ceratopsid
Diclonius	D. calamarius			"Teeth."[10]	Nomen dubium
	D. pentagonius			"Fragmentary dentary with teeth,"[10] type specimen	A dubious hadrosaurid
	D. perengulatus			"Teeth."[10]	Nomen dubium
Dysganus	D. bicarinatus			"Isolated teeth."[9]	Nomen dubium
	D. encaustus			"Single tooth and [five] tooth fragments."[10] "Isolated teeth."[9]	Nomen dubium
	D. haydenianus			"Isolated teeth."[9]	Nomen dubium
	D. peiganus			"Tooth."[9]	Nomen dubium
Hadrosaurus	H. paucidens				Reclassified as Lambeosaurus? paucidens
Judiceratops[11]	J. tigris[11]				A ceratopsid
?"Kritosaurus"	?"K." breviceps				A dubious hadrosaurid
?Lambeosaurus	?L. paucidens			"Squamosal, maxilla."[10]	Nomen dubium. An indeterminate lambeosaurine.[12]
Medusaceratops	M. lokii[13]			Bonebed[13]	A ceratopsid
Mercuriceratops	M. gemini[14]			"one apomorphic squamosal"[14]	A ceratopsid
Monoclonius	M. crassus[7]			"[Five] skulls, [one] complete."[8] Type specimen	A dubious ceratopsid
Paleoscincus	P. costatus			"Tooth,"[15] type specimen	A dubious ankylosaur
Probrachylophosaurus	P. bergei				A brachylophosaurin hadrosaur
Pteropelyx	P. grallipes			"Skeleton lacking skull."[16]	A dubious hadrosaurid
Trachodon	T. mirabilis			Isolated teeth, type specimen	A dubious hadrosaurid
Spiclypeus	S. shipporum			Partial skull, vertebrae, ribs, humerus, ilium, femur, tibia, and fibula.	A ceratopsid
Zuul	Z. crurivastator			Cranial and postcranial skeletal remains and soft tissue, type specimen	An ankylosaurid

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 alligatorid.
Deinosuchus	D. hatcheri[17]

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.

Theropod dinosaurs

Theropods reported from the Judith River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Aublysodon	A. lateralis			"Isolated teeth,"[18][19] type specimen	Junior synonym of Deinodon horridus[6]	Gorgosaurus Daspletosaurus Hesperornis Dromaeosaurus
	A. mirandus			Teeth, type specimen	Possible junior synonym of Deinodon horridus[6]
Hesperornis	H. altus			Partial tibiotarsus	One of the only known freshwater occurrences of a hesperornithid.[20]
Daspletosaurus	D. torosus			Maxilla[21]	A large tyrannosaurid.
Deinodon	D. falculus			Teeth	Isolated tyrannosaur teeth classified in the dubious genus Deinodon
	D. hazenianus			Teeth	Junior synonym of Deinodon horridus[6]
	D. horridus			"Teeth,"[19] type specimen	Isolated tyrannosaur teeth that formed the basis of the dubious genus Deinodon
	D. incrassatus			Teeth	Junior synonym of Deinodon horridus[6]
	D. lateralis				Junior synonym of Deinodon horridus[6]
Dromaeosaurus	D. albertensis			Teeth	A dromaeosaurid, also found in the Dinosaur Park Formation
	D. explanatus			"Tooth."[22]	Possible relative of Saurornitholestes
	D. laevifrons			"Tooth."[22]	Possible relative of Saurornitholestes
Gorgosaurus	G. libratus			Postorbital[21]	A large tyrannosaurid.
Ornithomimus	O. tenuis			"Fragmentary metatarsal."[23]	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
Troodon	T. formosus			Teeth (type specimen), egg	A troodontid, possibly dubious.
Zapsalis[24]	Z. abradens			"Teeth,"[22] type specimen	A dromaeosaurid

Turtles

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

See also

• List of dinosaur-bearing rock formations

References

1. Sullivan, R.M. and Lucas, S. G. (2006). "The Kirtlandian land-vertebrate "age"–faunal composition, temporal position and biostratigraphic correlation in the nonmarine Upper Cretaceous of western North America." Pp. 7-29 in Lucas, S. G. and Sullivan, R.M. (eds.), Late Cretaceous vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35.
2. Lexicon of Canadian Geological Units. "Judith River Formation". Retrieved 2009-02-06.
3. Hayden, F.V., 1871. Geology of the Missouri Valley: Preliminary report (4th annual) of the Geol. Surv. of Wyoming and portions of contiguous territories.
4. 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
5. Eberth, David A. (1997). "Judith River Wedge". In Currie, Philip J.; Padian Kevin (eds.). Encyclopedia of Dinosaurs. San Diego: Academic Press. pp. 379–380. ISBN 0-12-226810-5.
6. Sahni, A. (1972). "The vertebrate fauna of the Judith River Formation, Montana." Bulletin of the AMNH, v. 147 article 6: 321-415.
7. Ryan and Evans, 2005
8. "Table 23.1," in Weishampel, et al. (2004). Page 495.
9. "Table 23.1," in Weishampel, et al. (2004). Page 496.
10. "Table 20.1," in Weishampel, et al. (2004). Page 442.
11. Nicholas R. Longrich (2013). "Judiceratops tigris, a New Horned Dinosaur from the Middle Campanian Judith River Formation of Montana". Bulletin of the Peabody Museum of Natural History. 54 (1): 51–65. doi:10.3374/014.054.0103.
12. Prieto-Márquez, Alberto; Weishampel, David B.; Horner, John R. (2006). "The dinosaur Hadrosaurus foulkii, from the Campanian of the East Coast of North America, with a reevaluation of the genus" (PDF). Acta Palaeontologica Polonica. 51 (1): 77–98.
13. Ryan, Michael J.; Russell, Anthony P., and Hartman, Scott. (2010). "A New Chasmosaurine Ceratopsid from the Judith River Formation, Montana", In: Michael J. Ryan, Brenda J. Chinnery-Allgeier, and David A. Eberth (eds), New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium, Indiana University Press, 656 pp. ISBN 0-253-35358-0.
14. Ryan, Michael J.; Evans, David C.; Currie, Phillip J.; Loewen, Mark A. (2014). "A New chasmosaurine from northern Laramidia expands frill disparity in ceratopsid dinosaurs". Naturwissenschaften. doi:10.1007/s00114-014-1183-1
15. "Table 17.1," in Weishampel, et al. (2004). Page 368.
16. "Table 20.1," in Weishampel, et al. (2004). Page 443.
17. Schwimmer, David (2002). King of the Crocodylians: The Paleobiology of Deinosuchus. 601 North Morton Street, Bloomington, IN: Indiana University Press. p. 200.CS1 maint: location (link)
18. "Table 4.1," in Weishampel, et al. (2004). Page 78.
19. "Table 5.1," in Weishampel, et al. (2004). Page 114.
20. Fox, R.C. (1974). "A middle Campanian, nonmarine occurrence of the Cretaceous toothed bird Hesperornis Marsh." Canadian Journal of Earth Sciences, 11: 1335-1338.
21. Carr, Thomas D. (2018). "Significant geographic range extension for the sympatric tyrannosaurids Albertosaurus libratus and Daspletosaurus torosus from the Judith River Formation (Late Campanian) of northern Montana". Journal of Vertebrate Paleontology. 38 (Supplement 1): 102.
22. "Table 9.1," in Weishampel, et al. (2004). Page 186.
23. "Table 6.1," in Weishampel, et al. (2004). Page 139.
24. Larson, D. W.; Currie, P. J. (2013). "Multivariate Analyses of Small Theropod Dinosaur Teeth and Implications for Paleoecological Turnover through Time". In Evans, Alistair Robert. PLoS ONE 8: e54329. doi:10.1371/journal.pone.0054329. edit