# 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.

## 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.
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. 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.

## 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. | Tullock Member. | An isolated upper molar. | 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. | Tullock Member. | Fragmentary dentary & isolated teeth. | A leptictid. | |

#### Marsupials

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

#### Primatomorphs

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

#### Ungulates

Ungulates reported from the Fort Union Formation :
| Genus | Species | Locality | Stratigraphic member | Material | Notes |
| Dissacus | D. argenteus | Princeton Quarry, Park County, Wyoming. | Upper part of the formation. | Jaw elements & teeth. | A mesonychid. |
| Dissacus | D. cf. navajovius | Princeton Quarry, Park County, Wyoming. | Upper part of the formation. | Jaw elements & teeth. | Specimens reassigned to D. argenteus. |
| Dissacus | D. praenuntius | Park County, Wyoming. | Upper part of the formation. | Mandible (YPM-PU 16159). | A mesonychid also known from the Willwood Formation. |
| Ectocion | E. mediotuber | Princeton Quarry, Wyoming. | | Dentary. | A phenacodontid. |
| Periptychus | P. carinidens | Makoshika State Park, Montana. | | | A periptychid also found in the Nacimiento, North Horn, Black Peaks & Animas formations. |
| Sigynorum | S. magnadivisus | Great Divide Basin, southern Wyoming. | China Butte Member. | | 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.
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. | | | 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. | | Anterior end of left dentary (PU 16988). | A crocodilian. | |

#### Squamates

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

#### Testudines

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

### Amphibians

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

### Fish

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

### Invertebrates
#### Bivalves

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

#### Gastropods

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

### Plants

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