Fort Union Formation

The Fort Union Formation is a geologic unit containing sandstones, shales, and coal beds in Wyoming, Montana, and parts of adjacent states. In the Powder River Basin, it contains important economic deposits of coal, uranium, and coalbed methane.^[1]

Fort Union Formation
Stratigraphic range: Maastrichtian-Selandian (Lancian-Clarkforkian) ~66–58 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Fossils from the Fort Union Formation
Type	Geological formation
Sub-units	Atwell Gulch, China Butte, Ekalaka, Lebo, lower Ludlow, Overland, Rock Bench Quarry, Sentinel Butte, Shotgun, Somber beds, Tongue River, Tullock, upper Ludlow, Polecat Bench Formation
Underlies	Wasatch Formation
Overlies	Hell Creek Formation, Lance Formation
Lithology
Primary	Sandstone, shale
Other	Coal
Location
Coordinates	47.0°N 104.6°W / 47.0; -104.6
Approximate paleocoordinates	52.8°N 80.1°W / 52.8; -80.1
Region	Montana, North Dakota Wyoming, Colorado
Country	United States
Extent	Powder River Basin

Description

The Fort Union is mostly of Paleocene age and represents a time of extensive swamps as well as fluvial and lacustrine conditions. The rocks are more sandy in southwestern Wyoming and more coal-bearing in northeast Wyoming and southeast Montana, reflecting a general change from rivers and lakes in the west to swamps in the east, but all three environments were present at various times in most locations.^[2]

Coal in the Fort Union in the Powder River Basin occurs mainly in the Tongue River Member, where as many as 32 coal seams total more than 300 feet in thickness.^[1] One such bed, the Wyodak Coal near Gillette, Wyoming, is as much as 110 feet (34 m) thick. Most of the coals in the Fort Union Formation are ranked subbituminous.^[3]

Fort Union Formation - stratigraphy

Fossil content

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.

Mammals

Cimolestans

Cimolestans reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Crustulus	C. fontanus	Northeastern Montana.[4]	Tullock Member.[4]	An isolated upper molar.[4]	A pantodont.

Leptictids

Leptictids reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Prodiacodon	P. crustulum	Garfield & McCone counties, Montana.[5]	Tullock Member.[5]	Fragmentary dentary & isolated teeth.[5]	A leptictid.

Marsupials

Marsupials reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Peradectes	P. sp.	Swain Quarry, Wyoming.[6]		Upper & lower molars.[6]	Reassigned to Swaindelphys.
Swaindelphys	S. cifellii	Swain Quarry, Wyoming.[6]		Upper & lower molars.[6]	An opossum.

Primatomorphs

Primatomorphs reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Carpodaptes	C. sp.	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	2 isolated fourth lower premolars.[7]	A carpolestid.
Chiromyoides	C. caesor	Hell's Half Acre (UCM locality 78009), Mesa County, Colorado.[8]		A single upper incisor (UCM 53515).[8]	A plesiadapid.
	C. gigas	Piceance Creek Basin, Colorado.[8]		Multiple teeth.[8]	A plesiadapid.
	C. sp.	UCM locality 78060, Colorado.[8]		A left molar (UCM 41606).[8]	A plesiadapid.
Elphidotarsius	E. shotgunensis	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	Right ramus of mandible & isolated teeth.[7]	A carpolestid.
Nannodectes	N. gazini	Fremont County, Colorado.[8]		A right maxilla (USGS 16872).[8]	A plesiadapid.
Palaechthon	P., near P. alticuspis	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	3 upper molars & 4 lower molars.[7]	A plesiadapiform.
	P. woodi	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	A lower jaw & 13 isolated teeth.[7]	A plesiadapiform.
Palenochtha	P. cf. minor	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	5 lower teeth.[7]	A plesiadapiform.
Paromomys	P., near P. depressidens	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	Approximately 12 upper teeth, 8 isolated lower teeth & a jaw fragment.[7]	A paromomyid.
Phenacolemur	P. fremontensis	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	A lower jaw & isolated teeth.[7]	A paromomyid.
	P. cf. frugivorus	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	2 upper molars & 8 isolated lower molars.[7]	A paromomyid.
Plesiadapis	P. dubius	Piceance Creek Basin, Colorado.[8]		Jaw elements & teeth.[8]	A plesiadapid.
	P. fodinatus	Piceance Creek Basin, Colorado.[8]		Jaw elements & teeth.[8]	A plesiadapid.
	P. sp.	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	5 lower molars, 3 anterior upper molars & a premolar.[7]	A plesiadapid.
Plesiolestes	P. cf. problematicus	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	Approximately 45 isolated teeth.[7]	A plesiadapiform.
Pronothodectes	P. intermedius	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	Jaw elements & teeth.[7]	A plesiadapid.
Purgatorius	P. janisae	'Harley's Point’ UCMP locality V77087, Garfield County, Montana.[9]	Tullock Member.[9]	UCMP 150018 (right m1), and UCMP 192398 (left m3).[9]	A purgatoriid.
	P. mckeeveri	Garfield County, Montana.[9]	Tullock Member.[9]	Dentary remains & teeth.[9]	A purgatoriid.
	P. cf. P. mckeeveri	Harley's Point’ UCMP locality V77087, Garfield County, Montana.[9]	Tullock Member.[9]	UCMP 150019 (right M2), and UCMP 150020 (right M2).[9]	A purgatoriid.
Torrejonia	Cf. T. wilsoni	Wind River Basin, Wyoming.[7]	Shotgun Member.[7]	About 14 lower teeth & possibly 3 upper molars.[7]	A plesiadapiform.
Zanycteris	Z. honeyi	UMC locality number 92177, Colorado.[10]	Atwell Gulch Member.[10]	Right maxilla (UCM 87378).[10]	A plesiadapiform.

Ungulates

Ungulates reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Dissacus	D. argenteus	Princeton Quarry, Park County, Wyoming.[11]	Upper part of the formation.[11]	Jaw elements & teeth.[11]	A mesonychid.
	D. cf. navajovius	Princeton Quarry, Park County, Wyoming.[11]	Upper part of the formation.[11]	Jaw elements & teeth.[11]	Specimens reassigned to D. argenteus.
	D. praenuntius	Park County, Wyoming.[11]	Upper part of the formation.[11]	Mandible (YPM-PU 16159).[11]	A mesonychid also known from the Willwood Formation.
Ectocion	E. mediotuber	Princeton Quarry, Wyoming.[12]		Dentary.[12]	A phenacodontid.
Periptychus	P. carinidens	Makoshika State Park, Montana.[13]			A periptychid also found in the Nacimiento, North Horn, Black Peaks & Animas formations.
Sigynorum	S. magnadivisus	Great Divide Basin, southern Wyoming.[14]	China Butte Member.[14]		An arctocyonid.

Reptiles

Birds

A partial ornithurine coracoid bone found in this formation is identical to others found in the older Hell Creek Formation. At present, this unnamed species is the only known individual bird species that have survived the Cretaceous–Paleogene extinction event.^[15]

Birds reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Lithornis	L. celetius	Bangtail Quarry, Sedan Quadrangle, Park County, Montana.[16]			A lithornithid.

Crocodilians

Crocodilians reported from the Fort Union Formation
Genus	Species	Location	Stratigraphic member	Material	Notes	Images
Allognathosuchus	A. sp.	Princeton Quarry, Park County, Wyoming.[17]		Anterior end of left dentary (PU 16988).[17]	A crocodilian.

Squamates

Squamates reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Anguidae	Genus & species indeterminate	Swain Quarry, Carbon County, Wyoming.[18]		Fragmentary jaw elements.[18]	An anguid lizard.
cf. Anguidae		Swain Quarry, Carbon County, Wyoming.[18]		6 partial dentaries.[18]	Provisionally referred to anguid lizards based on size & shape.
Contogenys	cf. C. sloani	Swain Quarry, Carbon County, Wyoming.[18]		Posterior part of a right maxilla (AMNH 12069).[18]	A skink.
Exostinus	E. cf. E. lancensis	Swain Quarry, Carbon County, Wyoming.[18]		4 partial dentaries.[18]	A xenosaurid lizard.
	E. rugosus	Princeton & Schaff quarries, Park County, Wyoming.[17]		Multiple specimens.[17]	A xenosaurid lizard.
Glyptosaurinae	Genus & species indeterminate	Swain Quarry, Carbon County, Wyoming.[18]		Several jaw remains.[18]	A glyptosaurine lizard.
Glyptosaurinae or Odaxosaurinae	Genus & species indeterminate	Swain Quarry, Carbon County, Wyoming.[18]		Fragmentary jaw elements & osteoderms.[18]	Indeterminate lizard remains.
Machaerosaurus	M. torrejonensis	Swain Quarry, Carbon County, Wyoming.[18]		Numerous jaw elements.[18]	An anguid lizard also known from the Nacimiento Formation.
Odaxosaurus	O. piger	Swain Quarry, Carbon County, Wyoming.[18]		Many fragmentary jaw remains.[18]	An anguid lizard.
Oligodontosaurus	O. wyomingensis	Park County, Wyoming.[17]		A left mandible (PU 14246).[17]	An amphisbaenian.
Palaeosaniwa	cf. P. canadensis	Swain Quarry, Carbon County, Wyoming.[18]		Medial part of left dentary (AMNH 15957).[18]	A large anguimorph lizard.
Palaeoxantusia	P. fera	Swain Quarry, Carbon County, Wyoming.[18]		Numerous jaw elements.[18]	A night lizard.
Pancelosaurus	P. piger	Princeton, Fritz & Schaff quarries, Park County, Wyoming.[17]		Multiple skull elements.[17]	An anguid lizard.
Provaranosaurus	P. acutus	Princeton Quarry, Park County, Wyoming.[17]		PU 14243 (left maxilla), 14561 (anterior portion of left dentary) & 17145 ( fragment of left maxilla).[17]	A palaeovaranid lizard.
	cf. P. sp.	Swain Quarry, Carbon County, Wyoming.[18]		3 partial dentaries (AMNH 14306, 14307 & 14309).[18]	A palaeovaranid lizard.
Rhineuridae	Unidentified genus & species	Fritz Quarry, Park County, Wyoming.[17]		An almost complete right dentary & a broken vertebra (PU 18627).[17]	An amphisbaenian.
Saniwa	cf. S. sp.	Swain Quarry, Carbon County, Wyoming.[18]		2 trunk vertebrae (AMNH 15960 & 16003).[18]	A varanid.
Swainiguanoides	S. milleri	Swain Quarry, Carbon County, Wyoming.[18]		Jaw elements.[18]	An iguanid.

Testudines

Testudines reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Atoposemys	A. entopteros	Montana.[19]	Tullock Member.[19]		A softshell turtle.
Axestemys	A. montinsana	PTRM Site V02017, Slope County, North Dakota.[20]		Numerous skull, limb & shell fragments.[20]	A softshell turtle also found in the Melville & Denver formations.
Cardiochelyon	C. rogerwoodi	Reis Quarry, Park County, Wyoming.[21]		Partial skeleton (YPM PU14671).[21]	A kinosternoid formerly thought to be a platysternid.
Cedrobaena	C. putorius	Cedar Point Quarry, Wyoming.[22]		Shell & skull elements.[22]	A baenid turtle also found in the Hell Creek Formation.
Hutchemys	H. arctochelys	Burns Mine, Washoe Area, Carbon County, Montana.[23]	Tongue River Member.[23]	Multiple shell elements.[23]	A softshell turtle.
	H. rememdium	Fallon County, Montana.[23]	Ekalaka Member.[23]	A near complete postcranial skeleton (YPM PU 16795) & shell elements.[23]	A softshell turtle.
	H. sp.	Duffy's Ranch, Sweet Grass County, Montana.[23]		YPM PU 11566.[23]	A softshell turtle.
Ptychogaster	P. sp.	Princeton Quarry & Reiss Locality, Park County, Wyoming.[17]		PU 17794 (fragments of the skull & shell), 14671 & 16443 (shells).[17]	A turtle.
Tullochelys	T. montanus	Montana.[19]	Tullock Member.[19]		A chelydrid turtle also known from the Hell Creek Formation.

Amphibians

Amphibians reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Amphiuma	A. jepseni	Park County, Wyoming.[17]		PU 14666 (partial vertebral column), 14668 (partial skull) & 16788 (dislocated vertebrae).[17]	An aquatic salamander.
Anura	Incertae sedis	Park County, Wyoming.[17]		PU 14662 (distal end of right radioulna), 14663 (proximal end of left radioulna), 14669 (phalanx), 13372 (right maxilla).[17]	A frog.
Discoglossidae	Undescribed genus & species	Park County, Wyoming.[17]		Distal end of right humerus (PU 14670).[17]	A frog similar to undescribed discoglossid remains from the Hell Creek Formation.[17]
Eorhinophrynus	E. sp.	Princeton & Fritz quarries, Park County, Wyoming.[17]		Humeri & vertebrae.[17]	A burrowing toad.
Opisthotriton	O. kayi	Princeton Quarry, Park County, Wyoming.[17]		Multiple specimens.[17]	A salamander.
Scapherpeton	S. tectum	Princeton & Schaff quarries, Park County, Wyoming.[17]		PU 20583 (3 broken vertebrae, an atlas, an ilium & a rib) & PU 19500 (a humerus).[17]	A salamander.

Fish

Fish reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Acipenseridae	Morphotype A	Eagle Mine near Bear Creek, Carbon County, Montana.[24]		A complete lateral scute (YPM VPPU 17066).[24]	A large sturgeon.
	Morphotype B	Highway Blowout Site, Fallon County, Montana.[24]	Tongue River Member.[24]	A complete lateral scute (YPM VPPU 16646).[24]	A large sturgeon.
Amia	A. basiloides	Burns Mine and Eagle Mine near Bear Creek, Carbon County, Montana[25]		A near complete skull and partial skeleton, isolated vertebra[25]	A large bowfin.
Atractosteus	A. grandei	Bowman County, North Dakota.[26]	Lowest Danian strata.[26]		A large gar.
Cyclurus	C. fragosus	Schaff Quarry, Park County, Wyoming.[17]		3 vertebral centra (PU 21174).[17]	A bowfin.
Engdahlichthys	E. milviaegis	Montana.[27]	Tullock Member.[27]		A fairly small sturgeon.
Polyodon	P. tuberculata	Montana.[27]	Tullock Member.[27]	3 specimens.[27]	A paddlefish.

Invertebrates

Bivalves

Bivalves reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Pisidium	P. sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	8 specimens.[28]	A sphaeriid.
	P.? sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	3 specimens.[28]	A sphaeriid.
Plesielliptio	P. priscus	Powder River Basin.[28]	Tongue River Member.[28]	Numerous specimens.[28]	A unionid.
	cf. P. priscus	Powder River Basin.[28]	Tongue River Member.[28]	Several specimens.[28]	A unionid.
	P. silberlingi	Powder River Basin.[28]	Tongue River Member.[28]	Numerous specimens.[28]	A unionid.
	cf. P. silberlingi	Powder River Basin.[28]	Tongue River Member.[28]	6 specimens.[28]	A unionid.
	P. sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	2 specimens.[28]	A unionid.
Sphaeriidae	Gen. & sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	Numerous specimens.[28]	A sphaeriid.
Sphaerium	S. sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	1 specimen.[28]	A sphaeriid.
	S.? sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	Several specimens.[28]	A sphaeriid.
Unionidae	Gen. & sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	11 specimens.[28]	A unionid.

Gastropods

Gastropods reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Acroloxus	A.? minutus	Powder River Basin.[28]	Tongue River Member.[28]	2 specimens.[28]	A river limpet.
	A. sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	1 specimen.[28]	A river limpet.
Clenchiella	C. n. sp. A	Powder River Basin.[28]	Tongue River Member.[28]	Numerous specimens.[28]	A clenchiellid.
	C. n. sp. A?	Powder River Basin.[28]	Tongue River Member.[28]	1 specimen.[28]	A clenchiellid.
	C. cf. C. n. sp. A	Powder River Basin.[28]	Tongue River Member.[28]	10 specimens.[28]	A clenchiellid.
	C. sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	30 specimens.[28]	A clenchiellid.
Hydrobia	H. anthonyi	Powder River Basin.[28]	Tongue River Member.[28]	2 specimens.[28]	A hydrobiid.
	H. sp. A	Powder River Basin.[28]	Tongue River Member.[28]	Numerous specimens.[28]	A hydrobiid.
	H. cf. H. sp. A	Powder River Basin.[28]	Tongue River Member.[28]	2 specimens.[28]	A hydrobiid.
	H. sp. B?	Powder River Basin.[28]	Tongue River Member.[28]	Multiple specimens.[28]	A hydrobiid.
	H. sp. C?	Powder River Basin.[28]	Tongue River Member.[28]	1 specimen.[28]	A hydrobiid.
	H. sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	Multiple specimens.[28]	A hydrobiid.
	H.? sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	2 specimens.[28]	A hydrobiid.
Lioplacodes	L. multistriata	Powder River Basin.[28]	Tongue River Member.[28]	Numerous specimens.[28]	A viviparid.
	L. tenuicarinata	Powder River Basin.[28]	Tongue River Member.[28]	Numerous specimens.[28]	A viviparid.
	L. tenuicarinata?	Powder River Basin.[28]	Tongue River Member.[28]	11 specimens.[28]	A viviparid.
	L. limneaformis	Powder River Basin.[28]	Tongue River Member.[28]	Numerous specimens.[28]	A viviparid.
	L. sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	Numerous specimens.[28]	A viviparid.
	L.? sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	1 specimen.[28]	A viviparid.
Valvata?	V.? sp. indet.	Powder River Basin.[28]	Tongue River Member.[28]	1 specimen.[28]	A valvatid.
Viviparus	V. raynoldsanus	Powder River Basin.[28]	Tongue River Member.[28]	Numerous specimens.[28]	A viviparid.
	V. raynoldsanus?	Powder River Basin.[28]	Tongue River Member.[28]	1 specimen.[28]	A viviparid.
	V. cf. V. raynoldsanus	Powder River Basin.[28]	Tongue River Member.[28]	17 specimens.[28]	A viviparid.
	V. sp.	Powder River Basin.[28]	Tongue River Member.[28]	Multiple specimens.[28]	A viviparid.

Plants

Plants reported from the Fort Union Formation
Genus	Species	Locality	Stratigraphic member	Material	Notes	Images
Aesculus	A. hickeyi	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Leaves.[29]	A horse chestnut.
Amersinia	A. obtrullata	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Fruits.[29]	A nyssaceaen, may be produced by the same plant as Beringiaphyllum cupanioides.
Beringiaphyllum	B. cupanioides	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Leaf (UF 18969-60464).[29]	A nyssaceaen, may be produced by the same plant as Amersinia obtrullata.
Browniea	B. serrata	Mexican Hat locality & Custer National Forest, Powder River County, Montana.[29][30]	Lebo Member & Tongue River Member.[29][30]	Leaves showing signs of insect damage.[30]	A nyssaceaen.
Cercidiphyllum	C. genetrix	Mexican Hat locality, Montana.[30]	Lebo Member.[30]	Leaves showing signs of insect damage.[30]	A katsura tree.
Cornus	C. swingii	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Leaves.[29]	A dogwood.
Davidia	D. antiqua	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Leaves & fruits.[29]	A dove tree.
Cf. Dennstaedtia	Cf. D. americana	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	A single specimen of sterile foliage (UF 18969-34532).[29]	A fern.
Dicotylophyllum	D. hansonium	Williston Basin, North Dakota.[31]	Tongue River Member.[31]	Leaves.[31]	A dicot.
	D. horsecreekium	Williston Basin, North Dakota.[31]	Ludlow Member.[31]	Leaves.[31]	A dicot.
Eostangeria	E. pseudopteris	Sweetwater County, Wyoming.[32]	Upper part of the formation.[32]	Multiple specimens.[32]	A cycad.
Equisetum	E. sp.	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	A single stem (UF 18969-60476A).[29]	A horsetail.
"Ficus"	"F." artocarpoides	Mexican Hat locality.[30]	Lebo Member.[30]	Leaves with signs of hole feeding and insect mining.[30]	A fig-tree.
Glyptostrobus	G. europaeus	Mexican Hat locality.[30]	Lebo Member.[30]	Leafy branches.[30]	A conifer.
Juglandiphyllites	J. glabra	Mexican Hat locality, Montana.[30]	Lebo Member.[30]	Leaves with insect damage and probable lepidopteran leaf mines.[30]	A member of the walnut family.
Lauraceae	Species 1	Mexican Hat locality, Montana.[30]	Lebo Member.[30]	Leaf with piercing and sucking marks from insects.[30]
	Species 2	Mexican Hat locality, Montana.[30]	Lebo Member.[30]	Leaves showing signs of insect damage.[30]
Macginistemon	M. mikanoides	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Stamen groups.[29]	A platanaceaen.
Macginitiea	M. gracilis	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	A fragmentary leaf (UF 18969-38380).[29]	A platanaceaen.
	M. nascens	Williston Basin, North Dakota.[31]	Ludlow Member.[31]	Leaves.[31]	A platanaceaen.
Meliosma	M. thriviensis	Williston Basin, North Dakota.[31]	Ludlow Member.[31]	Leaves.[31]	A sabiaceaen.
	M. vandaelium	Williston Basin, North Dakota.[31]	Tongue River Member.[31]	Multiple leaves.[31]	A sabiaceaen.
Nordenskioeldia	N. borealis	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Fruit.[29]	A trochodendrale.
Paleonelumbo	P. macroloba	Mexican Hat locality, Montana.[30]	Lebo Member.[30]	Leaves.[30]	A nelumbonaceaen.
Paranymphaea	P. crassifolia	Mexican Hat locality, Montana.[30]	Lebo Member.[30]	Leaves.[30]	A nymphaeaceaen.
Phyllites	P. demoresii	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Leaves.[29]
Platanus	P. raynoldsii	Mexican Hat locality, Montana.[30]	Lebo Member.[30]	Leaves showing signs of insect damage.[30]	A plane-tree.
	P. sp.	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Leaves.[29]	A plane-tree.
Polyptera	P. manningii	Mexican Hat locality, Montana.[30]	Lebo Member.[30]	Fruits.[30]	A member of the walnut family.
"Populus"	"P". nebrascensis	Mexican Hat locality, Montana.[30]	Lebo Member.[30]	Leaves showing signs of insect damage.[30]	A poplar.
Porosia	P. verrucosa	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Fruits.[29]	A rutaceaen.
Taxodium	T. olrikii	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	[29]	A cypress tree.
Ternstromites	cf. T. aureavallis	Mexican Hat locality, Montana.[30]	Lebo Member.[30]	Leaf with a gall at the intersection of primary and secondary veins.[30]	A theaceaen.
	T. paucimissouriensis	Williston Basin, North Dakota.[31]	Ludlow & Tongue River Members.[31]	Leaves.[31]	A theaceaen.
Trochodendroides	T. genetrix	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	A few leaves.[29]	A saxifrage.
Ulmites	U. microphylla	Custer National Forest, Powder River County, Montana.[29]	Tongue River Member.[29]	Leaves.[29]	An ulmaceaen.
Zizyphoides	Z. flabella	Mexican Hat locality, Montana & Custer National Forest, Powder River County, Montana.[30][29]	Lebo Member & Tongue River Member.[30][29]	Leaves showing signs of insect damage.[30]	A trochodendrale.

See also

• List of fossiliferous stratigraphic units in Colorado
• List of fossiliferous stratigraphic units in Montana
• List of fossiliferous stratigraphic units in North Dakota
• List of fossiliferous stratigraphic units in Wyoming
• Uranium mining in Wyoming
• Guaduas Formation, contemporaneous coal-bearing formation of northern South America