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in: Cretaceous paleontological sites of North America, Geology of Montana, Geology of North Dakota,
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Hell Creek Formation

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Hell Creek Formation
Type Geological formation
Age Upper Cretaceous
Overlies Fox Hills Formation
Lithology
Location


The Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana.

The Hell Creek Formation occurs in Montana and portions of North Dakota, South Dakota, and Wyoming. In Montana, the Hell Creek Formation overlies the Fox Hills Formation and is the uppermost formation of the Cretaceous period. "Pompey's Pillar" at the Pompeys Pillar National Monument is a small isolated section of the Hell Creek Formation.

The Hell Creek Formation is well exposed in the badlands in the vicinity of Ft. Peck Reservoir.

The Hell Creek Formation is well exposed in the badlands in the vicinity of Ft. Peck Reservoir.

It is a series of fresh and brackish-water clays, mudstones, and sandstones deposited during the Maastrichtian, the last part of the Cretaceous period, by fluvial activity in fluctuating river channels and deltas and very occasional peaty swamp deposits along the low-lying eastern continental margin fronting the late Cretaceous Western Interior Seaway. The climate was mild, and the presence of crocodilians suggests a sub-tropical climate, with no prolonged annual cold. The famous iridium-enriched K-T boundary, which separates the Cretaceous from the Cenozoic, occurs as a discontinuous but distinct thin marker bedding within the Formation, near its uppermost strata.

Commercial excavations bring Hell Creek fossils onto the market, usually dinosaur teeth, crocodylian osteoderm fragments, and dermal plates of fossil gars. A representative selection of Hell creek fossils can be seen at the Museum of the Rockies, in Bozeman, Montana.

Fossils[]

The formation has produced impressive assemblages of invertebrates, plants, mammals, fish, reptiles, and amphibians. The most complete Hadrosaurid dinosaur ever found was retrieved in 2000 from the Hell Creek Formation and widely publicised in a National Geographic documentary aired in December 2007. A few bird and pterosaur fossils have also been found. Teeth of sharks and rays are sometimes found in the riverine Hell Creek Formation, suggesting that some of these taxa were tolerant of fresh water then as now.

Birds and other theropods[]

Theropod dinosaurs of the Hell Creek Formation
Taxa Presence Description Images

Genus:

  1. Avisaurus archibaldi
 An enantiornithine.
sp.

Chirostenotes sp.

Nanotyrannus

Tyrannosaurus

Genus:

  1. Chirostenotes sp.
 A large oviraptorosaur.
Family:
  1. cf. Dromaeosaurus sp.
  2. cf. Saurornitholestes sp.
  1. Placeholder.
  2. A very common dromaeosaurid.
  1. A dromaeosaurid, possibly a species of Dromaeosaurus.

Genus:

  1. Elmisaurus elegans
 An oviraptorosaur, possibly a species of Chirostenotes. Also found in the Judith River Formation.

Genus:

  1. Nanotyrannus lancensis
 A small tyrannosaur, possibly synonymous with Tyrannosaurus.

Genus:

  1. Ornithomimus sp.
 An ornithomimid.

Genus:

  1. Paronychodon lacustris
 A common coelurosaur, possibly dromaeosaurid. Also found in the Fruitland, Judith River, Lance, and Laramie Formations.

Genus:

  1. Richardoestesia gilmorei
 A common coelurosaur, possibly synonymous with Paronychodon. Also found in the Aguja, Judith River, Lance, Oldman, and Scollard Formations.

Genus:

  1. Struthiomimus sedens
 A large ornithomimid.[1]

Genus:

  1. Troodon sp.
 A troodontid.

Genus:

  1. Tyrannosaurus rex
 A tyrannosaur, known from several specimens including a juvenile nicknamed "Jane". Also found in the Denver, Frenchman, Hill Creek South, Javelina, Kirtland, Lance, McRae, North Horn, Scollard, and Willow Creek Formations.

Ornithischians[]

Ornithischian dinosaurs of the Hell Creek Formation
Taxa Presence Description Images

Genus:

  1. Anatotitan copei
 A "duck-billed" hadrosaur, possibly synonymous with Edmontosaurus.

Ankylosaurus

Edmontosaurus

Stygimoloch

Triceratops

Genus:

  1. Ankylosaurus magniventris
 An ankylosaur. Also found in the Lance and Scollard Formations.

Genus:

  • Bugenasaura
  1. Bugenasaura infernalis
 A small ornithopod.

Genus:

  1. Dracorex hogwartsia
 A pachycephalosaur, possibly synonymous with Pachycephalosaurus.

Genus:

  1. Edmontonia sp.
 An ankylosaur.

Genus:

  1. Edmontosaurus annectens
  2. Edmontosaurus regalis
  1. Very common.
  2. Very common.
  1. A hadrosaur. Also found in the Denver, Frenchman, Lance, Laramie, and Scollard Formations.
  2. A hadrosaur, very common. Also found in the Horseshoe Canyon, Lance, Laramie, Scollard, and St Mary River Formations.

Family:

  • Leptoceratopsidae
  1. cf. Leptoceratops sp.
  1. A primitive ceratopsian.

Genus:

  1. Pachycephalosaurus wyomingensis
 A pachycephalosaur. Also found in the Judith River and Lance Formations.

Genus:

  1. Parasaurolophus walkeri?
 A crested lambeosaurine hadrosaur. Also found in the Dinosaur Park Formation.

Genus:

  • Sphaerotholus
  1. Sphaerotholus bucholtzae
 A pachycephalosaur, possibly synonymous with Prenocephale.

Genus:

  1. Stygimoloch spinifer
 A pachycephalosaur, possibly synonymous with Pachycephalosaurus. Also found in the Lance Formation.

Genus:

  1. Thescelosaurus neglectus
 A small ornithopod. Also found in the Frenchman, Lance, Laramie, and Scollard Formations.

Genus:

  1. Torosaurus latus
 A ceratopsian. Also found in the Frenchman, Javelina, Kirtland, Lance, and North Horn Formations.

Genus:

  1. Triceratops horridus
  2. Triceratops prorsus
  1. Very common.
  2. Very common.
  1. A ceratopsian, very common. Also found in the Evanston, Frenchman, Kirtland, Lance, Laramie, and Scollard Formations.
  2. A ceratopsian, possibly be synonymous with T. horridus, very common. Also found in the Frenchman and Lance Formations.

Plants[]

Plants of the Hell Creek Formation
Taxa Presence Description Images

Genus:

  • Metasequoia
  1. Metasequoia sp.
 Casts of Dawn Redwood seed cones are known from the Hell Creek.

Genus:

  • Cobbania
  1. Cobbania corrugata
 A prehistoric species of water lettuce, previously assigned to the genus Pistia.

Pterosaurs[]

Pterosaurs of the Hell Creek Formation
Taxa Presence Description Images

Family:

  1. cf. Quetzalcoatlus sp.
 A single azhdarchid neck bone may belong to the genus Quetzalcoatlus.[2]

Quetzalcoatlus

See also[]

References[]

  1. ^ Longrich, N. (2008). "A new, large ornithomimid from the Cretaceous Dinosaur Park Formation of Alberta, Canada: Implications for the study of dissociated dinosaur remains." Palaeontology, 54(1): 983-996.
  2. ^ Henderson, M.D. and Peterson, J.E. "An azhdarchid pterosaur cervical vertebra from the Hell Creek Formation (Maastrichtian) of southeastern Montana." Journal of Vertebrate Paleontology, 26(1): 192–195.


External links[]

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