# 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 79 and 75.3 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 and the Oldman Formation of Alberta. 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.

## Lithology

The Judith River Formation is composed of mudstone, siltstone and sandstone. 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. 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 Judith River Formation is divided into four members, the Parkman Sandstone Member, the McClelland Ferry Member, the Coal Ridge member, and the Woodhawk Member. The McClelland Ferry Member (78.7-76.3 Ma) is believed to be equivalent to the Oldman Formation, with the Coal Ridge Member (76.3-75.3 Ma) equivalent to the Dinosaur Park Formation.

## Fauna

Faunal list follows a review published by Ashok Sahni in 1972 unless otherwise noted.
| 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 | Notes |
| 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. |

### Fish
#### Bony fish

Bony fishes of the Judith River Formation :
| Genus | Species | Location | Stratigraphic position | Abundance | Notes |
| Belonostomus | Belonostomus longirostris | | | | An aspidorhynchiform. |
| Cyclurus | C. fragosus | | | | A bowfin. |
| Lepisosteus | L. occidentalis | | | Scales | A gar. |
| ?Paralbula | ?P. sp. | | | | A bonefish. |
| Priscosturion | P. longipinnis | McClelland Ferry | Upper Campanian | | A sturgeon. |
| Psammorhynchus | P. longipinnis | McClelland Ferry | Upper Campanian | | Preoccupied name, renamed Priscosturion. |
| Polyodontidae | Indeterminate | | | | A paddlefish. Known remains exceeded size of Chinese paddlefish, total length would exceed 2 metres (6.6 ft). |

#### Cartilaginous fish

Cartilaginous fishes of the Judith River Formation :
| Genus | Species | Location | Notes |
| Myledaphus | M. bipartitus | | A stingray. |
| Cretalamna | C. sp | Montana | An Otodontid shark |
| Carcharias | Carcharias sp | | A sand tiger shark |
| Squalicorax | S.kaupi | | An Anacoracid shark |

### Plesiosaurs

Plesiosaurs of the Judith River Formation :
| Genus | Species | Location | Stratigraphic position | Abundance | Notes | Images |
| Plesiosauria | Plesiosauria indet. | | | | | |

### Pterosaurs

Pterosaurs of the Judith River Formation :
| Genus | Species | Location | Stratigraphic position | Abundance | Notes | Images |
| Azhdarchid | Azhdarchidae indet. | | | | | |

### 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 | Abundance | Notes | Images |
| Brachychampsa | B. montana | | An alligatorid. | Brachychampsa Deinosuchus |
| Leidyosuchus | L. canadensis | | An alligatoroid. | Brachychampsa Deinosuchus |
| Deinosuchus | D. hatcheri | Two giant dorsal vertebrae and a number of osteoderms. | An enormous alligatoroid. | Brachychampsa Deinosuchus |

### Lizards

Lizards of the Judith River Formation :
| Genus | Species | Notes |
| 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. |

### Ornithischians
#### Ankylosaurs

Ankylosaurs reported from the Judith River Formation :
| Genus | Species | Location | Member | Material | Notes | Images |
| Edmontonia | E. longiceps | | | Isolated teeth | A nodosaurid. | Edmontonia Zuul |
| Zuul | Z. crurivastator | | middle Coal Ridge | Cranial and postcranial skeletal remains and soft tissue, type specimen | An ankylosaurid. | Edmontonia Zuul |

#### Hadrosaurs

Hadrosaurs reported from the Judith River Formation :
| Genus | Species | Member | Material | Notes | Images |
| Brachylophosaurus | B. canadensis | middle McClelland Ferry | | A hadrosaurid which was one of the more common dinosaurs in the area. | Brachylophosaurus Probrachylophosaurus |
| Corythosaurus | C. sp. | middle Coal Ridge | two partial skeletons | A lambeosaurine hadrosaurid | Brachylophosaurus Probrachylophosaurus |
| Diclonius | D. calamarius | | "Teeth." | Nomen dubium | Brachylophosaurus Probrachylophosaurus |
| Diclonius | D. pentagonius | | "Fragmentary dentary with teeth," type specimen | A dubious hadrosaurid | Brachylophosaurus Probrachylophosaurus |
| Diclonius | D. perengulatus | | "Teeth." | Nomen dubium | Brachylophosaurus Probrachylophosaurus |
| Hadrosaurus | H. paucidens | | | Reclassified as Lambeosaurus? paucidens | Brachylophosaurus Probrachylophosaurus |
| ?"Kritosaurus" | ?"K." breviceps | | | A dubious hadrosaurid | Brachylophosaurus Probrachylophosaurus |
| ?Lambeosaurus | ?L. paucidens | | "Squamosal, maxilla." | Nomen dubium. An indeterminate lambeosaurine. | Brachylophosaurus Probrachylophosaurus |
| Paleoscincus | P. costatus | | "Tooth," type specimen | A dubious ankylosaur | Brachylophosaurus Probrachylophosaurus |
| Probrachylophosaurus | P. bergei | lower McClelland Ferry | | A brachylophosaurin hadrosaur | Brachylophosaurus Probrachylophosaurus |
| Pteropelyx | P. grallipes | | "Skeleton lacking skull." | A dubious hadrosaurid | Brachylophosaurus Probrachylophosaurus |
| Trachodon | T. mirabilis | | Isolated teeth, type specimen | A dubious hadrosaurid | Brachylophosaurus Probrachylophosaurus |

#### Marginocephalians
##### Ceratopsians

Ceratopsians reported from the Judith River Formation :
| Genus | Species | Location | Member | Material | Notes | Images |
| Albertaceratops | A. nesmoi | | | | Reclassified as Medusaceratops lokii | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Avaceratops | A. lammersi | | lower McClelland Ferry | "[Two] partial skulls, skeleton, juvenile," type specimen | A ceratopsid | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Ceratops | C. montanus | | | "occipital condyle, paired horn cores," type specimen | A dubious ceratopsid | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Dysganus | D. bicarinatus | | | "Isolated teeth." | Nomen dubium | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Dysganus | D. encaustus | | | "Single tooth and [five] tooth fragments." "Isolated teeth." | Nomen dubium | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Dysganus | D. haydenianus | | | "Isolated teeth." | Nomen dubium | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Dysganus | D. peiganus | | | "Tooth." | Nomen dubium | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Furcatoceratops | F. elucidans | Fergus County, Montana | Upper Coal Ridge | Nearly complete subadult skeleton. | A ceratopsid | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Judiceratops | J. tigris | | lower McClelland Ferry | | A ceratopsid | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Lokiceratops | L. rangiformis | Kennedy Coulee | lower McClelland Ferry | Disarticulated, associated skeleton including most of the skull and fragmentary postcrania | A ceratopsid | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Medusaceratops | M. lokii | | lower McClelland Ferry | Bonebed | A ceratopsid | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Mercuriceratops | M. gemini | | lower Coal Ridge | "one apomorphic squamosal" | A ceratopsid | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Monoclonius | M. crassus | | lower Coal Ridge | "[Five] skulls, [one] complete." Type specimen | A dubious ceratopsid | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |
| Spiclypeus | S. shipporum | | McClelland Ferry | Partial skull, vertebrae, ribs, humerus, ilium, femur, tibia, and fibula. | A ceratopsid | Avaceratops Judiceratops Furcatoceratops Lokiceratops Medusaceratops Mercuriceratops Spiclypeus |

##### Pachycephalosaurs

Pachycephalosaurs reported from the Judith River Formation :
| Genus | Species | Location | Member | Material | Notes | Images |
| Colepiocephale | C. lambei | Kennedy Coulee | lower McClelland Ferry | "nearly complete frontoparietal dome" | A pachycephalosaurid closely related to Stegoceras. | Colepiocephale |
| Hanssuesia | H. sternbergi | | | | A pachycephalosaurid. Also present in the Dinosaur Park and Oldman Formations. Possible synonym of Stegoceras. | Hanssuesia |

### Theropods
#### Dromaeosaurs

Dromeosaurs reported from the Judith River Formation :
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Dromaeosaurus | D. albertensis | Ox Hill Quarry, Careless Creek Quarry, Hidden Valley Quarry & Blackbird Ridge Quarry. | lower McClelland Ferry | Teeth | A dromaeosaurid, also found in the Dinosaur Park Formation | Dromaeosaurus Saurornitholestes |
| Dromaeosaurus | D. explanatus | | | "Tooth." | Possible relative of Saurornitholestes | Dromaeosaurus Saurornitholestes |
| Dromaeosaurus | D. laevifrons | | | "Tooth." | Possible relative of Saurornitholestes | Dromaeosaurus Saurornitholestes |
| Saurornitholestes | S. langstoni | Careless Creek, Emily's Ankle, Top Cat, Hidden Valley & Blackbird Ridge quarries. | Lower McClelland Ferry | Numerous teeth | A dromaeosaurid | Dromaeosaurus Saurornitholestes |
| Zapsalis | Z. abradens | | | "Teeth," type specimen | A dromaeosaurid | Dromaeosaurus Saurornitholestes |

#### Troodonts

Troodonts reported from the Judith River Formation :
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Theropod "A" | | Antelope Head, Careless Creek, Emily's Ankle, Top Cat, Hidden Valley, Blackbird Ridge & Jensen Ranch quarries. | | 28 teeth | Teeth of a large theropod distinct from those of tyrannosaurids | Troodon |
| Troodon | T. formosus | Antelope Head, Careless Creek, Emily's Ankle, Top Cat & Hidden Valley quarries. | | Teeth (type specimen), egg | A troodontid, possibly dubious. | Troodon |

#### Tyrannosaurs

Tyrannosaurs reported from the Judith River Formation :
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Aublysodon | A. lateralis | | | "Isolated teeth," type specimen | Junior synonym of Deinodon horridus | Daspletosaurus Gorgosaurus |
| Aublysodon | A. mirandus | | | Teeth, type specimen | Possible junior synonym of Deinodon horridus | Daspletosaurus Gorgosaurus |
| Daspletosaurus | D. torosus | | Coal Ridge | Maxilla | A large tyrannosaurid. | Daspletosaurus Gorgosaurus |
| Daspletosaurus | D. wilsoni | Jack’s B2 | lower Coal Ridge | Partial skull, cervical, sacral, and caudal vertebrae, and a rib, chevron, and first metatarsal | Originally considered to be a transitional species between D. torosus and D. horneri, though the validity of this claim has been questioned | Daspletosaurus Gorgosaurus |
| Daspletosaurus | D. sp. | | Coal Ridge | Partial skeleton | Not referrable to D. torosus | Daspletosaurus Gorgosaurus |
| Deinodon | D. falculus | | | Teeth | Isolated tyrannosaur teeth classified in the dubious genus Deinodon | Daspletosaurus Gorgosaurus |
| Deinodon | D. hazenianus | | | Teeth | Junior synonym of Deinodon horridus | Daspletosaurus Gorgosaurus |
| Deinodon | D. horridus | | | "Teeth," type specimen | Isolated tyrannosaur teeth that formed the basis of the dubious genus Deinodon | Daspletosaurus Gorgosaurus |
| Deinodon | D. incrassatus | | | Teeth | Junior synonym of Deinodon horridus | Daspletosaurus Gorgosaurus |
| Deinodon | D. lateralis | | | | Junior synonym of Deinodon horridus | Daspletosaurus Gorgosaurus |
| Gorgosaurus | G. libratus | | | Postorbital | A large tyrannosaurid, also found in the Dinosaur Park Formation and possibly the Two Medicine Formation. | Daspletosaurus Gorgosaurus |
| ?Tyrannosaurus | T. sp. | Fergus County | | A Lacrimal | found alongside a specimen of Deinosuchus, but may not be from the Judith River Formation | Daspletosaurus Gorgosaurus |

#### Other Theropods

Theropods reported from the Judith River Formation :
| Genus | Species | Location | Material | Notes | Images |
| Hesperornis | H. altus | | Partial tibiotarsus | One of the only known freshwater occurrences of a hesperornithid. | Hesperornis |
| Ornithomimus | O. tenuis | | "Fragmentary metatarsal." | A possible troodontid or juvenile tyrannosaurid | Hesperornis |
| Paronychodon | P. lacustris | | Teeth, type specimen | An indeterminate maniraptoran, also found in the Dinosaur Park, Milk River, and Kirtland Formations | Hesperornis |
| Richardoestesia | R. gilmorei | Careless Creek, Emily's Ankle, Hidden Valley & Blackbird Ridge quarries. | 12 teeth | A coelurosaur | Hesperornis |

### Turtles

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