Milk River Formation

Milk River Formation Stratigraphic range: Upper Cretaceous PreЄ Є O S D C P T J K Pg N
Outcrops along the Milk River
Type	Geological formation
Unit of	Montana Group
Sub-units	Telegraph Creek, Virgelle, Deadhorse Coulee Members
Overlies	Colorado Group
Thickness	up to 112 feet (30 m)[1]
Lithology
Primary	Sandstone
Other	Shale
Location
Named for	Milk River
Named by	Dowling, D.B., 1916[2]
Region	Alberta, Montana
Country	Canada,  United States

The Milk River Formation is a near- shore to terrestrial sedimentary unit deposited during the Late Cretaceous (late Santonian to early Campanian) in southern Alberta. It is equivalent to the marine Lea Park Formation of eastern Alberta, and the Eagle and Telegraph Creek Formations of north-central Montana, and to the upper part of the Niobrara Formation in Kansas.

In Alberta, the Milk River Formation is subdivided into the Telegraph Creek, Virgelle, and Deadhorse Coulee Members. The formation has produced an extensive but little known vertebrate fauna (see Table). Radiometric dates place deposition of the Milk River Formation between ~84.5 Ma and 83.5 Ma (Payenberg et al. 2002).

Members

• Telegraph Creek – The lowest member, it represents mudstone deposited just offshore in a marine setting. It has produced the ammonite index fossil Desmoscaphites bassleri (Payenberg et al. 2002), which has an age of ~84.5 Ma.

• Virgelle – Overlying the Telegraph Creek Member, it is a massive cliff-forming yellow to white sandstones. It was deposited in a shoreface environment, including beach, etc. (Payenberg et al. 2002).

• Deadhorse Coulee – Consists of shales, siltsones, sandstones, and coal beds. The Member was deposited in rivers, floodplains and swamps. Most of the vertebrate fossils come from this member.

There are some dinosaur remains from the Formation, but these are not very well known. A more concerted effort at locating specimens would undoubtedly produce many new taxa.

Vertebrates

(references: Brinkman 2003; Gao and Fox 1995; Hilton and Grande 2006; Larson 2008; Sullivan 2003; University of Alberta webpage)

Cartilaginous fishes

Remains of an indeterminate lamnid genus and species are present.

Cartilaginous fishes reported from the Milk River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes
Lonchidion	Indeterminate				Hybodontoidea
Myledaphus	M. bipartitus				Rhinobatoidei

Bony fishes

Remains of Acipenseridae, Amiidae, Esocidae, indeterminate genera and species.

Bony fishes reported from the Milk River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Belonostomus	Indeterminate				Aspidorhynchidae	Belonostomus Lepisosteus
Lepisosteus	L. occidentalis				Lepisosteidae
Palaeolabrus	Indeterminate				Lepisosteidae

Amphibians

Amphibians reported from the Milk River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Albanerpeton	A. galaktion				Albanerpetontidae	Albanerpeton
	A. nexuosus				Albanerpetontidae
Opisthotriton	Indeterminate				Batrachosauroididae

Squamates

Indeterminate Anguidae and Xenosauridae genera and species.

Squamates reported from the Milk River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes
Aocnodromeus	A. corrugatus				Scincidae
Chamops	Indeterminate				Teiidae
Coniophis	cf. C. precedens				Aniliidae
Cnephasaurus	C. locustivorus				Iguanidae
Glyptogenys	G. ornata				Teiidae
Parasaniwa?	Indeterminate				Necrosauridae
Penemabuya	P. antecessor				Scincidae
Sphenosiagon	S. simplex				Teiidae

Turtles

Indeterminate Solemydidae and Trionychidae genera and species.

Turtles reported from the Milk River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes
Adocus	Indeterminate				Adocidae
Basilemys	Indeterminate				Nanhsiungchelyidae
?Boremys	Indeterminate				Baenidae
?Compsemys	Indeterminate				Family indeterminant
Neurankylus	Indeterminate				Baenidae
Plesiobaena	Indeterminate				Baenidae

Crocodilians

Crocodilians reported from the Milk River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes
Gilchristosuchus	G. palatinus

Dinosaurs

Indeterminate Ankylosauridae, Aves, Ceratopsidae, Dromaeosauridae, Hadrosauridae, Nodosauridae, Ornithomimidae, Pachycephalosauridae, Protoceratopsidae, Thescelosauridae, and Tyrannosauridae genera and species.

Color key Taxon Reclassified taxon Taxon falsely reported as present Discredited taxon Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative data are in small text; crossed out data are discredited.

Dinosaurs reported from the Milk River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Brachyceratops[3]	Indeterminate[3]					Dromaeosaurus
Kritosaurus[4]	Indeterminate
Palaeoscincus[5]	Indeterminate
cf. Paronychodon[6]	cf. P. lacustris[6]				Theropoda incertae sedis
cf. Richardoestesia[6]	cf. R. gilmorei[6]				Maniraptora incertae sedis
	cf. R. isosceles				Maniraptora incertae sedis
Saurornitholestes[7]	S. langstoni[7]				Dromaeosauridae

Mammals

Other mammals

Other Mammals reported from the Milk River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes
Alticonodon	A. lindoei				Triconodontidae
Cimexomys	C. antiquus				Neoplagiaulacidae?
	C. magister				Neoplagiaulacidae?
Cimolodon	C. electus				Cimolodontidae
	C. similis				Cimolodontidae
Cimolomys	Indeterminate				Cimolomyidae
Ectypodus	cf. E. powelli
Meniscoessus	M. ferox				Cimolomyidae
Mesodma	Mesodma senecta
	Indeterminate
Mesodma	Mesodma senecta				Neoplagiaulacidae
	Indeterminate				Neoplagiaulacidae
Mictodon	Mictodon simpsoni				Tinodontidae
Paracimexomys	P. magister				Family indeterminent
Paranyctoides	Paranyctoides maleficus				Nyctitheriidae
Picopsis	P. pattersoni				Picopsidae
	Indeterminate				Picopsidae
Potamotelses	P. aquilensis				Potamotelsidae
Symmetrodontoides	S. canadensis				Spalacotheriidae
Viridomys	V. orbatus				Neoplagiaulacidae?

Didelphomorphs

Didelphomorphs reported from the Milk River Formation
Genus	Species	Location	Stratigraphic position	Material	Notes
Albertatherium	A. primus				Peradectidae
	A. secundus				Peradectidae
Alphadon	A. halleyi				Peradectidae
	Indeterminate				Peradectidae
Aquiladelphis	A. incus				Aquiladelphidae
	A. minor				Aquiladelphidae
Didelphodon	Indeterminate				Stagodontidae
Eodelphis	Indeterminate				Stagodontidae
Iqualadelphis	I. lactea				Pediomyidae
Pediomys	cf. P. clemensi				Pediomyidae
	P. exiguus				Pediomyidae
	P. florencae				Pediomyidae
Protalphadon	P. creber				Peradectidae

See also

• List of dinosaur-bearing rock formations

Footnotes

	Earth sciences portal
	Paleontology portal
	Dinosaurs portal

1. ^ Lexicon of Canadian Geological Units. "Milk River Formation". http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:009784. Retrieved 2009-02-06. 
2. ^ Dowling, D.B., 1916. Water Supply, Southeastern Alberta (Contains Geological Map 1604); Geological Survey of Canada, Summary Report 1915, pp. 102-110.
3. ^ ^{a b} Listed as "cf. Brachyceratops sp." in "1.4 Alberta, Canada; 5. Milk River Formation," in Weishampel, et al. (2004). Page 576.
4. ^ Listed as "cf. Kritosaurus sp." in "1.4 Alberta, Canada; 5. Milk River Formation," in Weishampel, et al. (2004). Page 576.
5. ^ Listed as "cf. Kritosaurus" in "1.4 Alberta, Canada; 5. Milk River Formation," in Weishampel, et al. (2004). Page 576.
6. ^ ^{a b c d} "1.4 Alberta, Canada; 5. Milk River Formation," in Weishampel, et al. (2004). Page 576.
7. ^ ^{a b} Listed as "cf. Saurornitholestes langstoni" in "1.4 Alberta, Canada; 5. Milk River Formation," in Weishampel, et al. (2004). Page 576.

References

• Brinkman, D. 2003. A review of nonmarine turtlesfrom the Late Cretaceous of Alberta. Canadian Journal of Earth Sciences 40:557-571.
• Gao, K., Fox, R.C. 1996. Taxonomy and evolution of late Cretaceous lizards (Reptilia: Squamata) from Western Canada. Bulletin of the Carnegie Museum 33: 1-107.
• Hilton, E.J. And Grande, L. 2006. Review of the fossil record of sturgeons, family Acipenseridae (Actinopterygii: Acipenseriformes), from North America. Journal of Paleontology 80: 672-683.
• Larson, D.W. 2008. Diversity and variation of theropod dinosaur teeth from the uppermost Santonian Milk River Formation (Upper Cretaceous), Alberta: a quantitative method supporting identification of the oldest dinosaur tooth assemblage in Canada. Canadian Journal of Earth Sciences 45: 1455-1468.
• Payenberg, T.H.D., Braman, D.R., Davis, D.W., and Miall, A.D. 2002. Litho- and chronostratigraphic relationships of the Santonian–Campanian Milk River Formation in southern Alberta and Eagle Formation in Montana utilising stratigraphy, U–Pb geochronology, and palynology. Canadian Journal of Earth Sciences 39:1553-1577.
• Sullivan, R.M. 2003. Revision of the dinosaur Stegoceras Lambe (Ornithischia, Pachycephalosauridae). Journal of Vertebrate Paleontology 23: 181-207.
• University of Alberta Museum http://www.museums.ualberta.ca/dig/search/vpaleo/index.html