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.
| Judith River Formation | |
|---|---|
| Stratigraphic range: Campanian, | |
 Judith River Formation, Upper Missouri Breaks National Monument | |
| Type | Geological formation |
| Unit of | Judith River Group |
| Sub-units | Parkman Sandstone Member, McClelland Ferry Member, Coal Ridge Member, Woodhawk Member |
| Underlies | Bearpaw Formation |
| Overlies | Claggett Formation, Pakowki Formation |
| Thickness | max 360 meters (1,180 ft) |
| Lithology | |
| Primary | Mudstone and sandstone |
| Location | |
| Region |  Montana |
| Country |  United States |
| Type section | |
| Named for | Judith River near the confluence with the Missouri River |
| Named by | F.V. Hayden, 1871; F.B. Meek, 1876. |
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
| Notes Uncertain or tentative taxa are in small text; |
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 | Location | Stratigraphic position | Abundance | Notes | Images | |
| H. dilatus | A siren. | ||||||
| L. bairdi | A scapherpetonid salamander. | ||||||
| O. kayi | A possible lungless salamander. | ||||||
| P. copei | |||||||
| S. tectum | A scapherpetonid salamander. | ||||||
Fish
Bony fish
| Bony fishes of the Judith River Formation | |||||||
|---|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Abundance | Notes | Images | |
| 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 | Stratigraphic position | Abundance | Notes | Images | |
| M. bipartitus | A stingray. | ||||||
Choristoderes
| Choristoderes of the Judith River Formation | |||||||
|---|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Abundance | Notes | Images | |
| C. sp. |  | ||||||
Crocodilians
| Crocodilians of the Judith River Formation | |||||||
|---|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Abundance | Notes | Images | |
| B. montana | An alligatorid. |   | |||||
| L. canadensis | An alligatorid. | ||||||
| Deinosuchus | D. hatcheri | Teeth | |||||
Lizards
| Lizards of the Judith River Formation | |||||||
|---|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Abundance | Notes | Images | |
| C. segnis | A whiptail. | ||||||
| Exostinus | E. lancensis | ||||||
| Leptochamops | L. denticulatus | A whiptail. | |||||
| P. bogerti | A parasaniwid. | ||||||
| Parasaniwa | P. wyomingensis | A parasaniwid. | |||||
Ornithischian dinosaurs
| Ornithischians reported from the Judith River Formation | |||||||
|---|---|---|---|---|---|---|---|
| Genus | Species | Location | Member | Material | Notes | Images | |
| A. nesmoi | Reclassified as Medusaceratops lokii |            | |||||
| A. lammersi | lower McClelland Ferry | "[Two] partial skulls, skeleton, juvenile," type specimen | A ceratopsid | ||||
| B. canadensis | middle McClelland Ferry | A hadrosaurid which was one of the more common dinosaurs in the area. | |||||
| C. montanus | "occipital condyle, paired horn cores," type specimen | A dubious ceratopsid | |||||
| Corythosaurus | C. sp. | middle Coal Ridge | two partial skeletons | A lambeosaurine hadrosaurid | |||
| D. calamarius | "Teeth." | Nomen dubium | |||||
| D. pentagonius | "Fragmentary dentary with teeth," type specimen | A dubious hadrosaurid | |||||
| D. perengulatus | "Teeth." | Nomen dubium | |||||
| D. bicarinatus | "Isolated teeth." | Nomen dubium | |||||
| D. encaustus | "Single tooth and [five] tooth fragments." "Isolated teeth." | Nomen dubium | |||||
| D. haydenianus | "Isolated teeth." | Nomen dubium | |||||
| D. peiganus | "Tooth." | Nomen dubium | |||||
| Edmontonia | E. longiceps | Isolated teeth | |||||
| Furcatoceratops | F. elucidans | Fergus County, Montana. | Upper Coal Ridge | Nearly complete subadult skeleton. | A ceratopsid | ||
| H. paucidens | Reclassified as Lambeosaurus? paucidens | ||||||
| Hanssuesia | H. sternbergi | A pachycephalosaurid. Also present in the Dinosaur Park and Oldman Formations. Possible synonym of Stegoceras. | |||||
| J. tigris | lower McClelland Ferry | A ceratopsid | |||||
| ?"Kritosaurus" | ?"K." breviceps | A dubious hadrosaurid | |||||
| ?L. paucidens | "Squamosal, maxilla." | Nomen dubium. An indeterminate lambeosaurine. | |||||
| M. lokii | lower McClelland Ferry | Bonebed | A ceratopsid | ||||
| M. gemini | lower Coal Ridge | "one apomorphic squamosal" | A ceratopsid | ||||
| M. crassus | lower Coal Ridge | "[Five] skulls, [one] complete." Type specimen | A dubious ceratopsid | ||||
| P. costatus | "Tooth," type specimen | A dubious ankylosaur | |||||
| P. bergei | lower McClelland Ferry | A brachylophosaurin hadrosaur | |||||
| P. grallipes | "Skeleton lacking skull." | A dubious hadrosaurid | |||||
| T. mirabilis | Isolated teeth, type specimen | A dubious hadrosaurid | |||||
| Spiclypeus | S. shipporum | McClelland Ferry | Partial skull, vertebrae, ribs, humerus, ilium, femur, tibia, and fibula. | A ceratopsid | |||
| Zuul | Z. crurivastator | middle Coal Ridge | Cranial and postcranial skeletal remains and soft tissue, type specimen | An ankylosaurid | |||
Theropod dinosaurs
| Theropods reported from the Judith River Formation | |||||||
|---|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images | |
| A. lateralis | "Isolated teeth," type specimen | Junior synonym of Deinodon horridus |    .jpg)  .JPG) | ||||
| A. mirandus | Teeth, type specimen | Possible junior synonym of Deinodon horridus | |||||
| H. altus | Partial tibiotarsus | One of the only known freshwater occurrences of a hesperornithid. | |||||
| Daspletosaurus | D. torosus | Coal Ridge Member | Maxilla and two partial skeletons | A large tyrannosaurid. | |||
| D. wilsoni | Jack’s B2 | 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 | ||||
| D. falculus | Teeth | Isolated tyrannosaur teeth classified in the dubious genus Deinodon | |||||
| D. hazenianus | Teeth | Junior synonym of Deinodon horridus | |||||
| D. horridus | "Teeth," type specimen | Isolated tyrannosaur teeth that formed the basis of the dubious genus Deinodon | |||||
| D. incrassatus | Teeth | Junior synonym of Deinodon horridus | |||||
| D. lateralis | Junior synonym of Deinodon horridus | ||||||
| D. albertensis | Ox Hill Quarry, Careless Creek Quarry, Hidden Valley Quarry & Blackbird Ridge Quarry. | Teeth | A dromaeosaurid, also found in the Dinosaur Park Formation | ||||
| D. explanatus | "Tooth." | Possible relative of Saurornitholestes | |||||
| D. laevifrons | "Tooth." | Possible relative of Saurornitholestes | |||||
| Gorgosaurus | G. libratus | Postorbital | A large tyrannosaurid, also found in the Dinosaur Park Formation and possibly the Two Medicine Formation. | ||||
| O. tenuis | "Fragmentary metatarsal." | A possible troodontid or juvenile tyrannosaurid | |||||
| P. lacustris | Teeth, type specimen | An indeterminate maniraptoran, also found in the Dinosaur Park, Milk River, and Kirtland Formations | |||||
| Richardoestesia | R. gilmorei | Careless Creek, Emily's Ankle, Hidden Valley & Blackbird Ridge quarries. | 12 teeth | A coelurosaur | |||
| Saurornitholestes | S. langstoni | Careless Creek, Emily's Ankle, Top Cat, Hidden Valley & Blackbird Ridge quarries. | Numerous teeth | A dromaeosaurid | |||
| 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 | ||||
| T. formosus | Antelope Head, Careless Creek, Emily's Ankle, Top Cat & Hidden Valley quarries. | Teeth (type specimen), egg | A troodontid, possibly dubious. | ||||
| Z. abradens | "Teeth," type specimen | ||||||
Turtles
| Turtles of the Judith River Formation | |||||||
|---|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Abundance | Notes | Images | |
| Adocus | A. sp. | ||||||
| B. sp. | |||||||
See also
References
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