| Type | Geological formation |
| Age | Campanian |
| Unit of | Judith River Group |
| Sub-units | Birch Lake Member, Ribstone Creek Member, Brosseau Member, Victoria Member |
| Underlies | Bearpaw Formation |
| Overlies | Claggett Formation, Pakowki Formation |
| Thickness | max 360 meters (1,181 ft)[1] |
| Lithology | |
| Primary | Siltstone and sandstone |
| Other | Coal, coquinas |
| Location | |
| Named for | Confluence of Judith River and Missouri River |
| Named by | F.V. Hayden, 1871;[2] F.B. Meek, 1876.[3]
|
| Region | Montana, Alberta, Saskatchewan |
The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the upper Cretaceous. 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.[1] Coal beds, bentonite and coquinas are also observed.
Fauna[]
Faunal list follows a review published by Ashok Sahni in 1972 unless otherwise noted.[4]
Amphibians[]
| Amphibians of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Family:
|
Disc-tongued frogs | |||
|
Genus:
|
A siren. | |||
|
Genus:
|
A scapherpetonid salamander. | |||
|
Genus:
|
A possible lungless salamander. | |||
|
Family:
|
Hip bones, possibly representing a North American member of the European spadefoot toad family. | |||
|
Genus:
|
A lungless salamander. | |||
|
Genus:
|
A scapherpetonid salamander. | |||
Ankylosaurian dinosaurs[]
| Ankylosaurs of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
Isolated tooth possibly belonging to Edmontonia. | |||
|
Genus:
|
Isolated tooth that formed the basis of the dubious genus Paleoscincus. | |||
Bony fish[]
| bony fish of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
An aspidorhynchiform. | |||
|
Genus:
|
A bowfin. | |||
|
Genus:
|
A gar. | |||
|
Genus:
|
A bonefish. | |||
Cartilaginous fish[]
| Cartilaginous fish of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
A stingray. | |||
Ceratopsian dinosaurs[]
| Ceratopsians of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
||||
|
Genus:
|
||||
|
Genus:
|
||||
|
Genus:
|
||||
Choristoderes[]
| Choristoderess of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
||||
Crocodilians[]
| Crocodilians of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
An alligatorid. | |||
|
Genus:
|
An alligatorid. | |||
Lizards[]
| Lizards of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
A whiptail. | |||
|
Genus:
|
A knob-scaled lizard. | |||
|
Genus:
|
A whiptail. | |||
|
Genus:
|
A parasaniwid. | |||
|
Genus:
|
A parasaniwid. | |||
|
Genus:
|
An anguid. | |||
Ornithopod dinosaurs[]
| Ornithopods of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
||||
|
Family:
|
||||
|
Subfamily:
|
||||
|
Genus:
|
Isolated teeth possibly belonging to Thescelosaurus. | |||
Pachycephalosaurian dinosaurs[]
| Pachycephalosaurs of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
Isolated teeth possibly belonging to Stegoceras or a similar dinosaur. | |||
Theropod dinosaurs[]
| Theropods of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
Isolated tyrannosaur teeth assigned to the dubious genus Aublysodon. | |||
|
Genus:
|
Isolated tyrannosaur teeth that formed the basis of the dubious genus Deinodon. | |||
|
Genus:
|
||||
|
Genus:
|
||||
|
Subamily:
|
||||
|
Genus:
|
||||
Turtles[]
| Turtles of the Judith River Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Description | Images | |
|
Genus:
|
A Mesoamerican river turtle. | |||
Relationship with other units[]
The Judith River Formation conformably overlies the Claggett Formation and Pakowki Formation. It is overlain by the Bearpaw Formation.[1] 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. To the east, it correlates with the sum of Oldman Formation and Foremost Formation.
Sub-divisions[]
The Birch Lake Member and Ribstone Creek Member are sandstone units recognized inside the Judith River Formation. Other informal subdivisions include the Brosseau Member and Victoria Member, which are considered obsolete due to their inconsistent lateral distribution.
See also[]
References[]
- ^ a b c Lexicon of Canadian Geological Units. "Judith River Formation". http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:007256. Retrieved on 2009-02-06.
- ^ Hayden, F.V., 1871. Geology of the Missouri Valley: Preliminary report (4th annual) of the Geol. Surv. of Wyoming and portions of contiguous territories.
- ^ Meek, Fielding Bradford, 1876. A report on the invertebrate Cretaceous and Tertiary fossils of the upper Missouri country, Hayden, F.V., Geologist in Charge; United States Geologic and Geographic Survey of the Territories, vol. 9, page 629
- ^ Sahni, A. (1972). "The vertebrate fauna of the Judith River Formation, Montana." Bulletin of the AMNH, v. 147 article 6: 321-415.
- ^ a b c Ryan and Evans, 2005
- ^ Stein and Triebold (2005). "Preliminary analysis of a sub-adult tyrannosaurid skeleton, known as "Sir William" from the Judith River Formation of Petroleum County, Montana." In The origin, systematics, and paleobiology of Tyrannosauridae, a symposium hosted jointly by Burpee Museum of Natural History and Northern Illinois University, p. 27-28.