Lakota Formation

The Lakota Formation is a sequence of rocks of early Cretaceous (Berriasian to Barremian) age from Western North America. Located in South Dakota, the name of the formation is derived from the Lakota Native American tribe.

Lakota Formation
Stratigraphic range: Berriasian-Barremian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Sub-units	Chilson Member. Fuson Member
Underlies	Fall River Formation
Overlies	Morrison Formation
Thickness	200 to 500 feet (60 to 150 m)
Lithology
Primary	Sandstone
Other	Shale, Coal, Conglomerate
Location
Region	North America
Country	United States
Type section
Named for	Lakota Native American tribe
Named by	Darton
Year defined	1899

There are two units of the Lakota Formation, the Chilson Member (upper Berriasian to Valanginian) and the underlying Fuson Member (upper Valanginian to early Barremian). A Berriasian-Valanginian age for the Chilson Member has been extrapolated by means of ostracods and charophytes.^[1]

The Fuson Member takes its name from rock exposures in Fuson Canyon, a valley on the eastern side of the Black Hills.^[2]

Vertebrate paleofauna

Dinosaurs

Dinosaurs reported from the Lakota Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Dakotadon[3]	D. lakotaensis		Chilson Member	"Skull, mandible, [and] vertebrae."[4]	An ankylopollexian iguanodont
Hoplitosaurus	H. marshi		Chilson Member	"Partial postcranial skeleton [and] osteoderms."[5]	An ankylosaur belonging to Polacanthidae
Osmakasaurus[6][7]	O. depressus		Chilson Member	Portions of both ilia, anterior part of the blade of one pubis, an incomplete sacrum, centrum of the last sacro-dorsal, 12 caudal vertebrae, 1 thoracic rib and many fragments	An ankylopollexian iguanodont
Macronaria[8]	Indeterminate		Chilson Member	Left humerus and right metacarpal I	A macronarian related to Camarasaurus

Mammals

Mammals reported from the Lakota Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Bolodon	B. hydei[9]		Chilson Member	Right M2	A plagiaulacid multituberculate
Infernolestes[9]	I. rougieri		Chilson Member	Right lower M1	A spalacotheriid trechnotherian.
Lakotalestes[9]	L. luoi		Chilson Member	Right upper molar (M5?)	A dryolestid
Passumys[9]	P. angelli		Chilson Member	Right M1	A plagiaulacid multituberculate

Turtles

Turtles reported from the Lakota Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Lakotemys[10]	L. australodakotensis		Chilson Member	Two shells and a partial skull	A baenid paracryptodire

Other vertebrate remains found within the Lakota Formation include a fish scale from the gar Lepisosteus and a crocodile tooth ^[11]