Hell Creek Formation

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Hell Creek Formation
Stratigraphic range: MaastrichtianDanian, 66.8–66 Ma
Hell Creek.jpg
Exposure in the badlands in the vicinity of Fort Peck Reservoir
Type Geological formation
Underlies Fort Union Formation
Overlies Fox Hills Formation
Location
Region  Montana  North Dakota  South Dakota
Country  USA

The Hell Creek Formation is an intensively-studied division of mostly Upper Cretaceous and some lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana. The formation includes portions of Montana, North Dakota, South Dakota, and Wyoming. In Montana, the Hell Creek Formation overlies the Fox Hills Formation. "Pompey's Pillar" at the Pompeys Pillar National Monument is a small isolated section of the Hell Creek Formation.

It is a series of fresh and brackish-water clays, mudstones, and sandstones deposited during the Maastrichtian and Danian (respectively the end of the Cretaceous period and the beginning of the Paleogene) 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 Cretaceous–Paleogene boundary, which separates the Cretaceous from the Cenozoic, occurs as a discontinuous but distinct thin marker bedding above and occasionally within the formation, near its boundary with the overlying Fort Union Formation.

The world's largest collection of Hell Creek fossils is housed and exhibited at the Museum of the Rockies, in Bozeman, Montana. The specimens displayed are the result of the museum's Hell Creek Project, a joint effort between the museum, Montana State University, the University of California, Berkeley, the University of North Dakota and the University of North Carolina which began in 1998.

Geology[edit]

Map of the Hell Creek and Lance formations in western North America

The Hell Creek Formation in Montana overlies the Fox Hills Formation and underlies the Fort Union Formation, and the boundary with the latter occurs near the Cretaceous-Paleogene boundary, which defines the end of the Cretaceous period and has been dated to 66 ± 0.07 Ma old.[1] Fauna characteristic of the Hell Creek (Lancian land vertebrate age) are found as high as a few meters below the boundary.[2]

The K-Pg boundary is generally situated near the contact between the upper Hell Creek and the lower Ludlow member of the Fort Union Formation, though in some areas (e.g. in North Dakota) the boundary is well within the Ludlow Member, 3 meters above the boundary with the Hell Creek in some areas.[2] On the other hand, in some small regions of Montana, the Hell Creek Formation contains the K-Pg boundary, and extends slightly into the Paleogene.[3]

Paleobiota[edit]

Many animals including dinosaurs lived in the Hell Creek Formation. The Hell Creek Formation has world-famous dinosaur fossil sites. Fossils are found of sea creatures from the recession and adjacent inland sea at that time. vertebrates include Dinosaurs, pterosaurs, crocodiles, champsosaurs, lizards, snakes, turtles, frogs and salamanders. Remains of fishes and mammals have also been found in the Hell Creek Formation. The formation has produced impressive assemblages of invertebrates (including Ammonites), plants, mammals, fish, reptiles (including the lizard Obamadon), Marine reptiles (including the marine reptiles like mosasaurs, plesiosaurs and sea turtles), and amphibians. Notable dinosaur finds include Tyrannosaurus and Triceratops. Ornithomimids as well, Caenagnathidae, a variety of small theropods, Pachycephalosaurs, Crocodylomorphs, and Squamates, including various animal fossils unearthed in the Hell Creek Formation. 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, mammal, and pterosaur fossils have also been found. The teeth of sharks and rays are sometimes found in the riverine Hell Creek Formation, suggesting that some of these taxa were then, as now, tolerant of fresh water. The "Lancian" fauna is more similar overall phylogenetically to East Asian and Canadian/Alaskan faunas then most Campanian North American faunas.

Depositional environment[edit]

At that time, 66 million years ago the appearance of the continent.
The dominant plants of the Hell Creek Formation are mainly angiosperms.

It is a series of fresh and brackish-water clays, mudstones, and sandstones deposited during the Maastrichtian and Danian (respectively the end of the Cretaceous period and the beginning of the Paleogene) 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 Hell Creek Formation, as typified by exposures in the Fort Peck area of Montana, has been interpreted as a flat forested floodplain, with a relatively subtropical climate that supported a variety of plants ranging from angiosperm trees, to conifers such as bald cypress, to ferns and ginkgos. The Hell Creek Formation was laid down by streams, on a coastal plain along the edge of the Western Interior Seaway. The climate was subtropical; there was no cold season and probably ample precipitation. The climate was mild, and the presence of crocodilians suggests a sub-tropical climate, with no prolonged annual cold. The Hell Creek Formation, Lance Formation and Scollard Formation represent different sections of the western shore of the shallow sea that divided western and eastern North America during the Cretaceous. Swampy lowland areas were the habitat of various animals, including dinosaurs. A broad coastal plain extended westward from the seaway to the newly formed Rocky Mountains. These formations are composed largely of sandstone and mudstone which have been attributed to floodplain, fluvial, lacustrine, swamp, estuarine and coastal plain environments.[4][5][6] Hell Creek is the best studied of these ancient environments. At the time, this region was subtropical, with a warm and moist climate. The climate was humid, with angiosperms, conifers, palmettos, and ferns in the swamps, and conifers, forest canopy, understory plants, Ash trees, live oak and shrubs in the forests. In northwestern South Dakota, strips of black layers deposited in the wetland environment are rich in coal, and a bright band-like layer of sand and mud from the river floodplain accumulated. Many plant species were supported, primarily angiosperms, and less commonly conifers, bald cypress, ferns and cycads. An abundance of fossil leaves are found at dozens of different sites indicating that the area was largely forested by small trees.

Invertebrates[edit]

Invertebrates reported from the Hell Creek Formation
Genus Species Location Stratigraphic position Material Notes Images

Plesielliptio

P. postbiplicatus

Fresh water Pelecypod.

P. gibbosoides

P. whitfieldi

Rhabdotophorus

R. aldrichi

Pleurobema

P. cryptorhynchus

Plethobasus

P. aesopiformis

P. biesopoides

Quadrula

Q. cylindricoides

Proparreysia

P. verrucosiformis

P. holmesiana

P. barnumi

P. percorrugata

P. pyramidatoides

P. letsoni

P. retusoides

P. corbiculoides

P. paucinodosa

Obovaria?

O?. pyramidella

Corbicula

C. cf. subelliptica

C. sp

From a marine facies ("tongue") in South Dakota. Modern members of this genus live in fresh water

Sphaerium

S. beckmani

"Pill clam". "Nut clam". "Fingernail clam". "Pea clam". Family Sphaeriidae.

Freshwater Fingernail Clam.gif

Pleiodon

Indeterminate

Campeloma

C. sp

Freshwater snail.

Anomia

A. gryphorhyncha

Bivalve. Family Anomiidae. From a marine facies ("tongue") in South Dakota.

Crassostrea

C. subtrigonalis

Oyster. Family Ostreidae. Collected from a marine facies ("tongue") in South Dakota.

Granocardium

G. sp

Bivalve. Family Cardiidae. Collected from a marine facies ("tongue") in South Dakota.

Hiatella?

H. sp

Bivalve. Present members of this genus are rock borers. Collected from a marine facies ("tongue") in South Dakota.

Leptosolen

indeterminate

Bivalve. Family Cultellidae. Collected from a marine facies ("tongue") in South Dakota.

Sphenodiscus

S. lenticularis

Ammonite. From a marine facies ("tongue") in South Dakota.

Discoscaphites

D. rossi

Microconch of an ammonite. From a marine facies ("tongue") in South Dakota.

Scaphitidae

indeterminate

Ammonite. From a marine facies ("tongue") in South Dakota. Other attributes: specimen has hooks on its shell.

Cephaloleichnites

C. strongi

hispine beetle. ("leaf beetle")

Amphibians[edit]

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 reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Anura[7]

indeterminate[7]

  • North Dakota[8]
  • South Dakota[8]

Middle to upper Hell Creek Formation[9]

3 unassigned specimens[10]

Anura indet. consists of material not currently assigned to any genus of anuran.[7]

Barbourula[11]

Indeterminate[12]

Caudata[7]

indeterminate[7]

  • North Dakota[8]
  • South Dakota[8]

Lower to uppermost Hell Creek Formation[9]

149 unassigned specimens[10]

Material of Caudata indet. is not currently assigned to any genus.[7]

Eopelobates[14]

Indeterminate[12]

Habrosaurus[7][12]

H. dilatus[7][12]

Middle to upper Hell Creek Formation[9]

6 specimens[10]

Habrosaurus is a sirenid amphibian.[7]

Lisserpeton[12]

L. bairdi[12]

Opisthotriton[7][12]

O. kayi[7][12]

Lower to upper Hell Creek Formation[9]

22 specimens[10]

Opisthotriton is classified as a Batrachosauroididae.[7]

Paranecturus[15]

P. garbanii[15]

A member of Proteidae.[15]

Proamphiuma[12]

P. cretacica[12]

Prodesmodon[12]

P. copei[12]

Scapherpeton[7][12]

S. tectum[7][12]

Lower to upper Hell Creek Formation[9]

144 specimens[10]

Scapherpeton is a scapherpetonid that is very common in the Hell Creek Formation.[7]

Scotiophryne[12]

S. pustulosa[12]

A small frog

Fishes[edit]

Bony fishes[edit]

Bony fishes reported from the Hell Creek Formation
Genus Species Location Stratigraphic position Material Notes Images

Acipenser[7][16]

A. eruciferus[16]

A sturgeon

cf. A. sp.[7]

  • North Dakota[8]
  • South Dakota[8]

Lower to upper Hell Creek Formation[9]

18 specimens are tentatively assigned to Acipenser sp.[10]

Acipenser sp. is tentatively referred to the genus.[7]

Amia[16]

A. fragosa[16]

small amiid fish (ubiquitous). Closely related to the modern Bowfin

Amia calva 1908.jpg

Melvius[7]

M. thomasi[7]

  • North Dakota[8]
  • South Dakota[8]

Lower to upper Hell Creek Formation[9]

6 specimens are assigned to Melvius[10]

A large amiid fish.[7]

Belonostomus[7][16]

B. longirostris[7][16]

Lower to upper Hell Creek Formation[9]

28 specimens[10]

A long-snouted slender fish classified as an aspidorhynchid.[7]

Coriops[18]

C. amnicolus[18]

Kindleia[7]

K. fragosa[7]

  • North Dakota[8]
  • South Dakota[8]

Lower to uppermost Hell Creek Formation[9]

2610 specimens have been assigned to Kindleia, making it an extremely common genus.[10]

Kindleia is a genus assigned to Amiidae, along with Melvius and Amia.[7]

Lepisosteus[7][16]

L. occidentalis[7][16]

Lower to uppermost Hell Creek Formation[9]

938 specimens are assigned to Lepidosteus[10]

A lepidosteid that is very common in the Hell Creek Formation.[7]

Lepisosteus oculatus1.jpg

Phyllodus

P. paulkatoi

fish with columnar teeth

Palaeolabrus[16]

P. montanensis[16]

Paleopsephurus[16]

P. wilsoni[16]

A paddlefish

Paddlefish underwater polyodon spathula.jpg

Palaeolabrus

P. montanensis

fish (incertae sedis)

Paralbula[20]

P. casei[20]

Platacodon[18]

P. nanus[18]

small teleost fish

Protamia[16]

Indeterminate[16]

Pachyrhizodontoidei

Indeterminate

Fish

Protoscaphirhynchus[16]

P. squamosus[16]

a sturgeon

Cartilaginous fishes[edit]

Cartilaginous fishes reported from the Hell Creek Formation
Genus Species Location Stratigraphic position Material Notes Images

Brachaelurus

B. estesi

Transferred to the genus Protoginglymostoma.

Chiloscyllium[21]

C. sp.[21]

A member of Hemiscylliidae.[21]

Chiloscyllium griseum Oceanopolis.jpg

Ischyrhiza[7][22]

I. avonicola[7][22]

Middle Hell Creek Formation[9]

5 specimens were assigned to Ischyrhinza[10]

Reported from the Hell Creek Formation on the basis of teeth that were subsequently identified as belonging to Myledaphus.[21]

Lissodus[7]

L. selachos[7]

Transferred to the genus Lonchidion. Extinct genus of freshwater shark.[21]

Lonchidion[22]

L. selachos[22]

Lower to upper Hell Creek Formation[9]

40 specimens[10]

A genus of prehistoric sharks in the family Hybodontidae. It makes up 0.4% of the remains of the vertebrates of the Hell Creek Formation.[7]

Myledaphus[21]

M. pustulosus[21]

Lower to upper Hell Creek Formation.[9]

1677 specimens[10] previously assigned to M. bipartitus.[21]

Is an anacoracid batoid[7] rajiform related to guitarfishes.[21] Described on the basis of teeth formerly assigned to the species M. bipartitus.[21] The material assigned to Myledaphus bipartitus and makes up 16.5% of the vertebrate remains.[7]

M. bipartitus[7]

  • North Dakota[8]
  • South Dakota[8]

Lower to Upper Hell Creek Formation[9]

material is now assigned to M. pustulosus.[21]

Myledaphus bipartitus remains are now assigned to M. pustulosus.[21]

Protoginglymostoma[21]

P. estesi[21]

A member of Ginglymostomatidae.[21] Formerly assigned to the genus Brachaelurus.

Nurse shark.jpg

Restesia[21]

R. americana[21]

Middle Hell Creek Formation[9]

5 specimens previously assigned to Squatirhina[10]

A wobbegong.[21] Formerly assigned to Squatirhina. The remains consist of 0.05% of the vertebrates.[10] Also known from the Lance Formation.[21]

Spotted wobbegong.jpg

Squatirhina[7]

S. americana[7]

  • North Dakota[8]
  • South Dakota[8]

Middle Hell Creek Formation[9]

Material is now assigned to Restesia.[21]

Squatirhina material is now assigned to Restesia.[21]

Rikr0076 - Flickr - NOAA Photo Library.jpg

Dinosaurs[edit]

A paleo-population study is one of the most difficult of analyses to conduct in field paleontology. Here is the most recent estimate of the proportions of the eight most common dinosaurian families in the Hell Creek Formation, based on detailed field studies by White, Fastovsky and Sheehan (1998).

Ceratopsidae 61%

Hadrosauridae 23%

Ornithomimidae 5%

Tyrannosauridae 4%

Hypsilophodontidae 3%

Dromaeosauridae 2% (represented only by teeth)

Pachycephalosauridae 1%

Troodontidae 1% (represented only by teeth)

Pie chart of the time averaged census for large-bodied dinosaurs from the entire Hell Creek Formation in the study area.

Outcrops sampled by the Hell Creek Project were divided into three sections: lower, middle and upper slices. The top and bottom sections were the focus of the PLoS One report, and within each portion many remains of Triceratops, Edmontosaurus, and Tyrannosaurus were found. Triceratops was the most common in each section, but, surprisingly, Tyrannosaurus was just as common, if not slightly more common, than the hadrosaur Edmontosaurus. In the upper Hell Creek section, for example, the census included twenty two Triceratops, five Tyrannosaurus, and five Edmontosaurus.

The dinosaurs Thescelosaurus, Ornithomimus, Pachycephalosaurus, and Ankylosaurus were also included in the breakdown, but were relatively rare. Small predatory dinosaurs, such as Troodon, were reported as being rare and are not included in the breakdown.

The dinosaur collections made over the past decade during the Hell Creek Project yielded new information from an improved genus-level collecting schema and robust data set that revealed relative dinosaur abundances that were unexpected, and ontogenetic age classes previously considered rare. We recognize a much higher percentage of Tyrannosaurus than previous surveys. Tyrannosaurus equals Edmontosaurus in U3 and in L3 comprises a greater percentage of the large dinosaur fauna as the second most abundant taxon after Triceratops, followed by Edmontosaurus. This is surprisingly consistent in (1) the two major lag deposits (MOR loc. HC-530 and HC-312) in the Apex sandstone and Jen-rex sand where individual bones were counted and (2) in two-thirds of the formation reflected in L3 and U3 records of dinosaur skeletons only.

Triceratops is by far the most common dinosaur at 40% (n = 72), Tyrannosaurus is second at 24% (n = 44), Edmontosaurus is third at 20% (n = 36), followed by Thescelosaurus at 8% (n = 15), Ornithomimus at 5% (n = 9), and Pachycephalosaurus and Ankylosaurus both at 1% (n = 2) are relatively rare.

Ornithischians[edit]

Ankylosaurs[edit]

Ankylosaurs reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Ankylosaurus[24]

Ankylosaurus magniventris[24]

An ankylosaur. Also found in the Lance and Scollard Formations.

Ankylosaurus magniventris.jpg Ankylosaurus dinosaur.png

Edmontonia[24]

Edmontonia sp.[24]

A nodosaur ankylosaurian.

Edmontonia dinosaur.png Dinosaur exhibit - Houston Museum of Natural Science - DSC01881.JPG

Pachycephalosaurs[edit]

An undescribed Pachycephalosaur is present in North Dakota.[26]

Pachycephalosaurs reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Dracorex[27]

D. hogwartsia[27]

A pachycephalosaur, possibly synonymous with Pachycephalosaurus.

The Childrens Museum of Indianapolis - Dracorex skeletal reconstruction.jpg Dracorex 3.jpg

Pachycephalosaurus[24]

P. wyomingensis[24]

A pachycephalosaur. Also found in the Lance Formation.

Pachycephalosauria jmallon.jpg Pachycephalosaurus in Japan.jpg Pachycephalosaurus head butting.png

Sphaerotholus[24]

S. buchholtzae[24]

"Skull material."[28]

A pachycephalosaur, possibly synonymous with Prenocephale.

Sphaerotholus.png

Stygimoloch[24]

S. spinifer[24]

  • Montana[24]
  • South Dakota
  • North Dakota

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

Berlin Naturkundemuseum Dino Schaedel.jpg Stygi.jpg

Ceratopsians[edit]

Indeterminate ceratopsid specimens are extremely common. 8.31% of all vertebrate remains from the Hell Creek Formation are unassigned ceratopsids.[10]

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.
Ceratopsians reported from the Hell Creek Formation
Genus Species Synonyms State Stratigraphic position Material Notes Images

Leptoceratops[24]

Leptoceratops c.f. gracilis[24]

A small primitive-looking ceratopsian.

Leptoceratopsidae - Leptoceratops.JPG Leptoceratops BW.jpg

Tatankaceratops

T. sacrisonorum

  • South Dakota

A ceratopsian possibly synonymous with Triceratops[29]

Tatankaceratops NT.jpg

Torosaurus[7][24]

T. latus[7][24]

Upper Hell Creek Formation[9]

A ceratopsian possibly synonymous with Triceratops.[30] A rare ceratopsid.[9]

Ceratopsian.jpg Torosaurus.tif

Triceratops[7][24]

T. horridus[7][24]

Lowermost to upper Hell Creek Formation[9]

4 specimens are assigned to Triceratops horridus from the Hell Creek Formation[10]

A ceratopsian.[7] Also found in the Evanston, Frenchman, Kirtland, Lance, Laramie, and Scollard Formations.

Triceratops-goulandris-head.jpg Triceratops Struct.jpg Fossil of Triceratops Raymond.jpg

T. prorsus[24]

Very common.[citation needed]

Also found in the Frenchman and Lance Formations.

Triceratops mount.jpg Triceratopsskull.jpg

Ornithopods[edit]

Indeterminate hadrosaurid remains are very common in the Hell Creek Formation.[7] A lambeosaurine hadrosaur similar to Parasaurolophus may have lived in the Hell Creek Formation however lack of more evidence makes this unclear.[24]

Ornithopods reported from the Hell Creek Formation
Genus Species Synonyms State Stratigraphic position Material Notes Images

Edmontosaurus

E. annectens

  • Anatosaurus annectens[31]
  • Anatotitan copei[31]
  • Montana[24]
  • South Dakota[25]
  • North Dakota(Mummy Fossil)

Very common.

A hadrosaur. Also found in the Denver, Frenchman, Lance, Laramie, and Scollard Formations.

Edmontosaurus annectens skull.jpg DMNS Edmontosaurus.png Edmontosaurus HMNS.jpg

Thescelosaurus[25]

T. garbanii[32]

  • Bugenasaura garbanii

Burpee - Thescelosaurus.JPG Thescelosaurus neglectus, CMN.jpg

T. infernalis

  • Bugenasaura infernalis

Nomen dubium

T. neglectus[7][25]

Lower to upper Hell Creek Formation[9]

50 specimens[10]

A small ornithopod. Also found in the Frenchman, Lance, Laramie, and Scollard Formations.[34]

Thescelosaurus neglectus.jpg Willogeneral.jpg

Theropods[edit]

A theropod closely related to, and of overall similarity to, the feathered Asian genus Mononykus.

Theropod tracks have been found in South Dakota.[25] An unnamed alvarezsaurid, closely related to the Asian genus Mononykus, is known from Montana.[35] A second footprint that may have been made by a Tyrannosaurus was first reported in 2007 by British paleontologist Phil Manning, from the Hell Creek Formation of Montana. This second track measures 72 centimetres (28 in) long, shorter than the track described by Lockley and Hunt. Whether or not the track was made by Tyrannosaurus is unclear, though Tyrannosaurus and "Nanotyrannus" are the only large theropods known to have existed in the Hell Creek Formation. Palaeontologists known for years that there are oviraptorosaurs found in the Hell Creek Formation, but the fossil remains of the group remain relatively scarce. The velociraptorine Acheroraptor is also present in the latest Maastrichtian layers of the formation.

Tyrannosaurids[edit]

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.
Tyrannosaurids reported from the Hell Creek Formation
Genus Species Synonyms State Stratigraphic position Material Notes Images

Tyrannosaurus[7][24]

T. rex[7][24]

  • Albertosaurus megagracilis[24]
  • Aublysodon molnari[24]
  • Dinotyrannus megagracilis[24]
  • Nanotyrannus lancensis

Lower to upper Hell Creek Formation.

A tyrannosaur, known from several specimens including a juvenile nicknamed "Jane". Also found in the Denver, Frenchman, Hill Creek South, Javelina, Kirtland, Lance, Ferris, Tornillo, Livingston, McRae, North Horn, Scollard, Willow Creek Formation, and also found in Lomas Coloradas Formations.

Tyrannosaurus Rex Growth Series.jpg T-Rex.jpg Jane Tyrannosaurus.jpg Sues skeleton.jpg Tyrannoskull.jpg

Tyrannosauridae[24]

Indeterminate[24]

  • Aublysodon cf. mirandus[24]
Remains that cannot be assigned to any particular species.

Partial Tyrannosaurus tooth UCMP.JPG

Ornithomimosaurs[edit]

Ornithomimid remains are not uncommon in the Hell Creek Formation.[7] 15 specimens from the Hell Creek Formation are undetermined ornithomimids[10]

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.
Ornithomimids reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

"Orcomimus"

unnamed

An ornithomimid. Numem nudum

Ornithomimus - claw.jpg

Ornithomimus[24]

O. velox[24]

An ornithomimid. Hell Creek remains actually intermediate ornthimimids.

OrnithomimusROM.JPG Ornithomimus edmontonicus.jpg

Struthiomimus[25]

S. sedens[38]

  • Montana
  • South Dakota
  • North Dakota

A large ornithomimid similar to Gallimimus in size.[38]

Struthiomimus ROM.jpg Struthiomimus.JPG

Oviraptorosaurs[edit]

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.
Oviraptorosaurs reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Anzu[24][39]

A. wyliei[39]

12 well-preserved specimens[9]

Lower to upper Hell Creek Formation[10]

It was thus one of the largest known oviraptorosaurs and the largest known from North America. Material previously assigned to Caenagnathidae indet. is now placed in the genus Anzu.[39]

Chirostenotes skull.jpg Anzu MRF 319 specimens.png

Leptorhynchos[39]

L. elegans

  • Montana

Alternately classified as a species of Elmisaurus, E. elegans is originally known from the Campanian Dinosaur Park Formation. A partial caenagnathid foot, specimen MOR 752, from the Hell Creek Formation has sometimes been referred to E. elegans.

Oviraptorid Clean.png

Eumaniraptorans[edit]

Historically, numerous teeth have been attributed to various dromaeosaurid and troodontid taxa with known body fossils from only older formations, including Dromaeosaurus, Saurornitholestes, Richardoestesia, Troodon, and Paronychodon. However, in a 2013 study, Evans et al. concluded that there is little evidence for more than a single dromaeosaurid taxon, Acheroraptor, in the Hell Creek-Lance assemblages, which would render these taxa invalid for this formation. But did not found yet.[40] Indeterminate Dromaeosaurid have also been found in the Hell Creek Formation.

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.
Eumaniraptorans reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Acheroraptor[40]

A. temertyorum [40]

Lower? to upper Hell Creek Formation[7]

Partial skull (one isolated maxilla, one dentary), teeth.[40]

A velociraptorine dromaeosaurid. Teeth previously referred to Campanian dromaeosaurids Saurornitholestes and Dromaeosaurus, frequently found throughout the formation, probably belong to this one species. Evans et al. conclude that there is little evidence for more than a single dromaeosaurid taxon, A. temertyorum, in the Hell Creek-Lance assemblages.[40]

Acheroraptor reconstruction.jpg Acheroraptor.jpg

Avisaurus[7][24]

A. archibaldi[7][24]

Middle Hell Creek Formation[9]

One specimen from the Hell Creek Formation can be assigned to Avisaurus[10]

An avisaurid.[7]

Cimolopteryx[24]

C. maxima[24]

It is known almost exclusively from a number of coracoids (a bone in the shoulder girdle).

A Charadriiformes bird

Cimolopteryx.jpg

Brodavis[41]

B. baileyi[41]

Left tarsometatarsus missing proximal end, trochleae II and III.[41]

A hesperornithiform.[41]

Hesperornis regalis (1).jpg

Potamornis[41]

P.skutchi [42]

the quadrate bone is unique in some respects but apparently shares more apomorphies with the family Hesperornithidae - the "typical" Hesperornithes - in cladistic analysis

A hesperornithiform.[41]

Skeleton of Parahesperornis alexi.jpg Hesperornis BW.jpg

"Unnamed hesperornithiform A"[43]

Indeterminate

Tarsometatarsus

A primitive hesperornithiform.[43] In addition to fossils from the Hell Creek Formation, Longrich, Tokaryk and Field (2011) assigned specimen RSM P 2315.1 from the Canadian Frenchman Formation to this taxon as well;[43] subsequently Martin, Kurochkin and Tokaryk (2012) made this particular specimen the holotype of the species Brodavis americanus.[41]

"Unnamed ornithurine B"[43]

Indeterminate[44]

Partial coracoid

An ornithurine possibly similar to Cimolopteryx[43][44]

"Unnamed ornithurine C"[43]

Indeterminate

Partial coracoid

An ornithurine, also present in the Fort Union Formation, the only individual bird species known to have survived the Cretaceous–Paleogene extinction[43]

"Unnamed ornithurine D"[43]

Indeterminate

Partial coracoid

An ornithurine[43]

Pterosaurs[edit]

Pterosaurs of the Hell Creek Formation
Taxa Species State Stratigraphic location Material Notes Images

Azhdarchidae spp.

Indeterminate

  • Montana[46]
  • North Dakota

Records of pterosaur remains from the Hell Creek Formation are two indeterminate specimens, which have been recorded from North Dakota but not described (Johnson et al., 2000; Pearson et al., 2002). A single azhdarchid neck bone may belong to the genus Quetzalcoatlus, thought are not diagnostic to the generic level.[46]

Crocodylomorphs[edit]

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.
Crocodylomorphs reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Borealosuchus[47]

  • B. sternbergii[47]
  • Montana
  • North Dakota
  • South Dakota

Extinct genus of crocodylians that lived from the Late Cretaceous to the Eocene in North America.

Borealosuchus species.jpg Borealosuchus wilsoni 1.jpg

Brachychampsa[47]

  • Montana
  • South Dakota
  • North Dakota

Extinct genus of alligatoroid.

Brachychampsa sp. - Natural History Museum of Utah - DSC07244.JPG Brachychampsa sp. - Natural History Museum of Utah - DSC07238.JPG

Thoracosaurus[47]

  • T. neocesariensis[47]
  • Montana

Extinct genus of gavialoid crocodilian which existed during the Late Cretaceous and early Paleocene.

Thoracosaurus macrorhynchus - Maastricht.jpg Thoracosaurus.jpg

Turtles[edit]

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.
Turtles reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Adocus[48]

Indeterminate[48]

Extinct genus of aquatic turtles belonging to the family Adocidae.

Adocidae - Adocus punctatus.jpg

Compsemys[48]

C. victa[48]

A relative of Dermatemydidae.

Peckemys

P. brinkman

  • Montana
  • North Dakota

A relative of Baenidae.

Emarginachelys

E. cretacea

  • Montana

A relative of chelydrids.[50]

Eubaena[48]

E. cephalica[48]

Baenid turtle

Gamerabaena

G. sonsalla

  • North Dakota

Extinct genus of baenid turtle.

Palatobaena

P. cohen

  • North Dakota

A relative of extinct family of cryptodiran turtles.

Cedrobaena

C. putorius

  • South Dakota
  • North Dakota

A relative of Baenidae.

Gilmoremys

G. lancensis

  • Montana
  • North Dakota

Trionychidae related to the softshell turtle.

Hoplochelys[50]

H. clark[50]

A kinosternoid related to the Central American river turtle.[50]

Plastomenus

P. sp

Trionychidae turtle.

Basilemys

B. sinuosa

Largest dermatemydid land tortoise.

Trionyx[48]

Indeterminate[48]

A genus of softshell turtles belonging to the family Trionychidae.

Trionychidae - Trionyx messelianus.JPG

Aspideretoides

A. foveatus

Trionychidae turtle.

Helopanoplia

H. distincta

Trionychidae turtle.

Clemmys

C. backmani

Thin-shelled macrobaenid turtle.

Clemmys guttata - Buffalo Zoo.jpg

Plesiobaena

P. antiqua

Baenid turtle.

Stygiochelys

S. estesi

Baenid turtle.

Neurankylus

N. eximius

Largest baenid turtle in Hell Creek Formation.

Baena arenosa AMNH 1112.jpg

Thescelus

T. insiliens

Baenid turtle.

Chelydridae

Indeterminate

Chelydrids-like turtle.

Squamates[edit]

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.
squamates reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Cemeterius[51][52]

C. monstrosus[51][52]

A platynotan lizard of uncertain phylogenetic placement, also known from the Lance Formation.[51]

Cerberophis[51][52]

C. robustus[51][52]

An alethinophidian snake of uncertain phylogenetic placement.[51]

Obamadon[51][52]

O. gracilis[51][52]

A polyglyphanodontian lizard of uncertain phylogenetic placement. Also known from the Lance Formation.[51]

Peneteius[51]

P. aquilonius[51]

A chamopsiid polyglyphanodontian lizard.[51]

Haptosphenus

H. placodon

Teiidae lizard.

Goldteju Tupinambis teguixin.jpg

Leptochamops

L. denticulatus

Small Teiidae lizard.

Chamops

C. segnis

Largest Teiidae lizard in Hell Creek Formation

Contogenys

C. sloani

Scincidae? lizard.

Exostinus

E. lancensis

xenosaurid lizard.

Chin-krokodilschwanzechse-01.jpg

Proxestops

P. jepseni

Anguidae lizard.

Parasaniwa

P. wyomingensis

Necrosaurid lizard.

Paraderma

P. bogerti

Helodermatidae? lizard.

Palaeosaniwa

P. canadensis

A large Monstersauria lizard, closely related to today's varanid lizards. It was the largest lizard in the Hell Creek formation.

Boidae

Indeterminate

Snake. Earliest-known boid.

Boa constrictor (2).jpg

Choristoderans[edit]

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.
Choristoderans reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Champsosaurus[47]

C. sp.[47]

  • Montana

champsosaur.

Champsosaurus BW.jpg Large williston champsosaurus.jpg

Mammals[edit]

Multituberculates[edit]

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.
Multituberculates reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Cimexomys[53]

C. minor[53]

A multituberculate of uncertain phylogenetic placement.

Cimexomys minor.jpg

Cimolodon[53]

C. nitidus

  • Montana
  • North Dakota[53]

A cimolodontid multituberculate.

C. cf. nitidus[53]

A cimolodontid multituberculate.

C. sp.[53]

A cimolodontid multituberculate.

Cimolomys[53]

C. gracilis

A cimolodontid multituberculate.

Ptilodus.jpg

  • C. cf. gracilis[53]

A cimolomyid multituberculate.

Essonodon[53]

E. browni[53]

A cimolomyid multituberculate.

Meniscoessus[53]

M. conquistus

A cimolomyid multituberculate.

Meniscoessus skull.jpg

M. robustus

  • Montana
  • North Dakota
  • South Dakota[53]

A cimolomyid multituberculate.

Meniscoessus robustus.jpg

M. cf. robustus

A cimolomyid multituberculate.

M. sp.

A cimolomyid multituberculate.

?M. sp.[53]

A cimolomyid multituberculate.

Mesodma[53]

M. formosa

  • Montana
  • South Dakota[53]

A neoplagiaulacid multituberculate.

M. cf. formosa

A neoplagiaulacid multituberculate.

M. hensleighi

  • Montana
  • South Dakota[53]

A neoplagiaulacid multituberculate.

M. cf. hensleighi

A neoplagiaulacid multituberculate.

M. thompsoni

  • Montana
  • North Dakota
  • South Dakota[53]

A neoplagiaulacid multituberculate.

M. cf. thompsoni

A neoplagiaulacid multituberculate.

M sp.[53]

A neoplagiaulacid multituberculate.

?M sp.[53]

A neoplagiaulacid multituberculate.

?Neoplagiaulax[53]

?N. burgessi[53]

A neoplagiaulacid multituberculate.

Paracimexomys[53]

P. priscus[53]

A multituberculate of uncertain phylogenetic placement.

Paressonodon[54]

P. nelsoni[54]

A cimolomyid multituberculate.

Stygimys

S. kuszmauli

  • Montana

It was a member of the extinct order Multituberculata.

Metatherians[edit]

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.
Metatherians reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Alphadon[53]

A. marshi

  • Montana
  • North Dakota[53]

An alphadontid. genus of small, primitive mammal that was a member of the Metatheria, a group of mammals that includes modern-day marsupials.

A. cf. marshi

  • Montana
  • South Dakota[53]

An alphadontid.

A. wilsoni

An alphadontid.

A. cf. wilsoni

An alphadontid.

A. sp.[53]

  • North Dakota
  • South Dakota[53]

An alphadontid.

Didelphodon[53]

D. padanicus

A stagodontid.

D. vorax

  • Montana
  • North Dakota[53]

A stagodontid. genus of Stagodontidae marsupials from the Late Cretaceous of North America.

The Childrens Museum of Indianapolis - Didelphodon mandible.jpg Didelphodon Clean.png

D. cf. vorax

A stagodontid.

Didelphodon Skull Clean.png

D. sp.

A stagodontid.

cf. D. sp.[53]

  • North Dakota
  • South Dakota[53]

A stagodontid.

Glasbius[53]

G. twitchelli

A glasbiid.

G. cf. twitchelli[53]

A glasbiid.

Leptalestes[55]

L. cooki

A pediomyid.

L. krejcii[55]

  • Montana
  • South Dakota[53]

A pediomyid.

Nanocuris[54]

N. improvida[54]

A deltatheridiid.

Nortedelphys

N. jasoni (= N. intermedius)[54][56]

  • Montana
  • South Dakota

A herpetotheriid.

Pediomys[53]

P. elegans[53]

  • Montana
  • South Dakota[53]

A pediomyid.

Protalphadon[53]

P. foxi

An alphadontid.

P. lulli[53]

An alphadontid.

Protolambda[55]

P. florencae

  • Montana
  • North Dakota
  • South Dakota[53]

A pediomyid.

P. hatcheri[55]

  • Montana
  • South Dakota[53]

A pediomyid.

Turgidodon[53]

T. rhaister[53]

An alphadontid.

Eutherians[edit]

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.
Eutherians reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Purgatorius

P. ceratops

  • Montana

A genus of the four extinct species believed to be the earliest example of a primate or a proto-primate.

Purgatorius BW.jpg

Alostera[53]

A. saskatchewanensis[53]

A eutherian of uncertain phylogenetic placement.

Batodon[53]

B. tenuis[53]

A cimolestid eutherian.

Cimolestes[53]

C. cf. cerberoides

A cimolestid eutherian.

C. incisus

A cimolestid eutherian.

C. magnus

  • Montana
  • North Dakota[53]

A cimolestid eutherian.

C. propalaeoryctes

A cimolestid eutherian.

C. stirtoni[53]

A cimolestid eutherian.

Gypsonictops[53]

G. hypoconus

  • Montana
  • South Dakota[53]

A gypsonictopsid eutherian.

G. illuminatus

  • Montana
  • North Dakota[53]

A gypsonictopsid eutherian.

G. cf. illuminatus

A gypsonictopsid eutherian.

G. sp.[53]

A gypsonictopsid eutherian.

cf. Paranyctoides[53]

cf. Paranyctoides sp.[53]

A nyctitheriid eutherian.

Protungulatum[55]

P. coombsi[55]

A eutherian of uncertain phylogenetic placement; a basal eutherian or an arctocyonid condylarth.

Protungulatum donnae.JPG

Plants[edit]

Although the first representatives of leafy trees and true grasses emerged in the Cretaceous, the flora was still dominated by conifers like Araucaria.

The Hell Creek Formation was a low flood plain at the time before the sea retreated, and in the wet ground of the dense woodland, laurels, sycamores, beech, magnolias, and palm trees grew. Ferns and moss grew in the forest understory. Plant fossils from the upper early Paleocene of the Hell Creek Formation include the ferns Botrychium, Woodwardia, Osmunda, Onoclea and Azolla; Conifers Metasequoia, Cupressaceous conifers and Glyptostrobus; the monocot Limnobiophyllum (a relative of duckweeds); and the dicots Cercidiphyllum and Platanus.[57][58] There are numerous types of leaves, seeds, flowers and other structures from Angiosperms, or flowering plants. The Hell Creek Formation of this layer contains 300 tablets or more of plants. Angiosperms are by far the most diverse and dominant flora of the entire population, about 90 percent. However, the evergreens included conifers, ginkgo, bald cypress, and cycads. Flowering plants included a variety of trees that no longer exist. Today Hell Creek's flora is hardwood forest mixed with deciduous and evergreen forest and apparently similar to then, but with a closer look, the current plant community is distinct. In sharp contrast to Montana today, the presence of palm trees meant the climate was warmer then.

Fossil fruit Spinifructus antiquus of unknown family and order, from the Hell Creek Formation in Montana

Dr. Kirk Johnson (Scientist) claims that there are no grasses, oaks, maples, or willows in the Hell Creek Formation. Ferns are uncommon in the majority of the formation, however there is a great increase in the abundance of fossil fern spores in the two centimeters of rock that directly overlies the impact fallout layer (the famous K-T boundary layer). This increase in fern spore abundance is commonly referred to as "the fern spike" (meaning that if the abundance of spores as a function of stratigraphic position were plotted out, the graph would show a spike just above the impact fallout layer). Johnson also found that the majority of the angiosperm genera in the Hell Creek Formation are now extinct. He also believes that, very roughly, 80% of the terrestrial plant taxa died out in what is now Montana and the Dakotas at the K/T boundary.

Many of the modern plant affinities in the Hell Creek Formation (e.g., those with the prefix "aff." or with quotes around the genus name) may not in reality belong to these genera; instead they could be entirely different plants that resemble modern genera. Therefore, there is some question regarding whether the modern Populus or Juglans, as two examples, actually lived in the late Cretaceous.

Compared to the rich Hell Creek Formation fossil plant localities of the Dakotas, relatively few plant specimens have been collected from Montana. A few taxa were collected at Brownie Butte Montana by Shoemaker, but most plants were collected from North Dakota (Slope County) and from South Dakota. "TYPE" after the binomial means that it is represented by a type specimen found in the Yale-Peabody Museum collections. "YPM" is the prefix for the Yale-Peabody Museum specimen number.

Overview (from Johnson, 1997): 190 plant morphotypes, including:

  • 1 bryophyte (mosses and liverworts)
  • 6 "pteridophytes" (A paraphyletic group: modern examples are horsetails, club mosses and ferns.)
  • 9 conifers
  • 2 ginkgo (uncommon)
  • 172 angiosperms (90% of all specimens collected, as well as 90% of all taxa found)


Plant of the Hell Creek Formation:

Gymnosperms

Ginkgos

Angiosperms

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.

AquilapollenitesreductusAquilapollenitesturbidus

Plant of the Hell Creek Formation
Genus Species Location Stratigraphic position Abundance Notes Images

Aquilapollenites

Aquilapollenitesattenuatus

Aquilapollenitescollaris

Aquilapollenitesconatus

Aquilapollenitesdelicatus

Aquilapollenitesmarmarthensis

Aquilapollenitesquadricretaeus

Aquilapollenitesquadrilobus

Aquilapollenitessenonicus

Aquilapollenitesstriatus

Aquilapollenites Attenuatus Funkhouser(1961).jpg

Alnipollenites

Ficus

Ficusplanicostata

Sycomoros old.jpg

Ficusartocarpoides

Ficustrinervis

Ilexpollenites

Ilexpollenites compactus

Interpollis

Interpollis cf. I. supplingensis

Balmeisporites

Balmeisporites sp.

Marmarthia

Marmarthia pearsonii

Myrica

Myricatorreyi

Myrica faya.jpg

Platanites

Platanites marginata

Sabalites

Sabalites sp.

Tricolpites

Tricolpites interangulus

Metasequoia

M. sp

Casts of Dawn Redwood seed cones are known from the Hell Creek.

MetaseqLeaves.jpg

Grewiopsis

Gsaportana

Another generic Hamamelididae.

Annona?

A?. robusta

Abundant at Brownie Butte, Montana.

Annona muricata Blanco1.196.png

Cobbania

C. corrugata

A prehistoric species of water lettuce, previously assigned to the genus Pistia.

Pistia stratiotes0.jpg

Araucaria

A. araucana

Casts of Monkey-puzzle leaves are found in Hell Creek.

Araucaria araucana cones.jpg

Artocarpus

A. lessigiana

Abundant at Brownie Butte, Montana.

Artocarpus.altilis1web.jpg

Celastrus

C. taurenensis

Some may be Eucommiacaea.

Celastrus scandens.jpg

Cinnamomum

c. lineafolia

Included in "Ficus" affinis by L. Hickey. Belongs in Rhamnaceae (modern buckthorns and Ceanothus). Some other specimens referred to Cinnamomum sezanensis(?) sp.), a real cinnamon bush.

CinnamonLeaves.jpg

Cissu

C. marginata

Also spelled "marginatus".

Juglans

J. leconteana

Juglans major Morton.jpg

Liriodendrites

L. bradacci

Johnson, 1996. In the Magnoliidae: a common taxon.

Liriodendron

L. laramiense

May be related to today's tulip tree (yellow poplar).

Liriodendron tulipifera.jpg

Leepiesceia

L. presrtocarpoides

another laurel.

Marmarthia

M. pearsonii

Johnson, 1996. In the Lauraceae: a common taxon.

Lauraceae sp Blanco2.360.png

M. trivialis

Johnson, 1996. In the Lauraceae: a common taxon.

Platanites

P. marginata

Johnson, 1996. In the Platanaceae: Hamamelididae. A common taxon.

London plane flower.jpg

Quercus

Q. viburnifolia

Included within "Cissus" marginata. May be in the Platanaceae.

Dombeyopsis

D. trivialis

Included within "Cissus" marginata. May be in the Platanaceae.

D. obtusa

Included within "Cissus" marginata. May be in the Platanaceae.

Rhamnus

R. cleburnii

A buckthorn look-alike.

Rhamnus frangula - Köhler–s Medizinal-Pflanzen-120.jpg

Vitis

V. stantonii

This could be a real Vitus (a real grape).

Abhar-iran.JPG

Ziziphus

Z. fibrillosus

Zizyphus zizyphus Ypey54.jpg

Androvettia

A. catenulata

Araliaephyllum

A. polevoi

Bisonia

B. niemii

Incertae sedis. Johnson, 1996. A broad leaf, probably in the Laurales. A common taxon. Type specimen was found near a Tyrannosaurus skeleton in South Dakota.

Cannabaceae

C. sp

Cannabis 01 bgiu.jpg

Cissites

C. insignis

May belong in Hamemelididae.

C. lobata

C. puilasokensis

Cupressinocladus

C. interruptus

Dombeyopsis

D. trivialis

Elatides

E. longifolia

In Platanales, according to Leo Hickey.

Erlingdorfia

E. montana

Johnson, 1996. In the Platanaceae: Hamamelididae (related to today's Sycamore). A common taxon.

Gingko

G. adiantoides

The only gingko in the Hell Creek Formation; uncommon

Ginkgo adiantoides - G. cranii.jpg

Glyptostrobus

G. nordenskioldii

Glyptostrobus 01.jpg

G. sp

Glyptostrobus pensilis 2007.06.28 10.10.35-p6280031.jpg

Laurophyllum

L. wardiana

Magnolia

M. pulchra

This species was thought to occur only in southern Wyoming flora, but Leo Hickey claims it is found further north in Montana and the Dakotas.

M.macrophylla var. ashei 200706.jpg

Marchantia

M. pealii

MarchantiaPolymorpha.jpg

Nilssonia

N. yukonensis

The only Hell Creek Formation cycad. Uncommon. A distant living relative is our sago palm.

Cycad leaves semicircle.jpg

Onoclea

O. hesperia

Paranymphaea

P. hastata

Platanophyllum

P. montanum

Porosia

P. verrucosa

Rhamnus

R. salicifolius

Another buckthorn look-alike. Abundant at Brownie Butte, Montana

Rhamnus frangula.jpg

Sabalites

S. sp

Palm tree.

Puka beach.jpg

Sapindopsis

S. powelliana

Sequoites

S. artus

Sequoia tree.

Del Norte Titan 230.jpg

Taxodium

T. olrikii

Related to today's bald cypress.

Taxodium distichum NRCSMS01010.jpg

Trochodendroides

T. arctica

T. nebrascensis

Zingiberopsis

Z. attenuata

Related to today's ginger plant. Its closest living relative is the Asian genus Alpinia. Some Hell Creek Formation. specimens show damage from hispine beetles ("leaf beetles" (Wilf et al., 2000)).

Zingiber officinale Blanco1.131.png

Dryophyllum

D. subfalcatum

One of the most common plant taxa in the Hell Creek and Lance Formations. Common at Brownie Butte, Montana. If it is close to real Dryophyllum then it is a beech/chestnut-like tree (Fagaceae). It may also be a walnut-like tree (Juglandaceae).

D. tenneseensis

see above.

aff. "Dryophyllum" subfalcatum

sea above.

Populus

P. nebrascensis

Populus tremula 002.jpg

Cocculus

cf. C. flabella

Cocculus orbiculatus HRM.jpg

Cissites

cf. C. acerifolia

Pistia

cf. P. corrugata

Floating aquatic herb.

Pistia stratiotes 2.jpg

Palaeoaster

P. inquirenda

Angiosperm. Produces large seed pods.

See also[edit]

Footnotes[edit]

  1. ^ Husson, D., Galbrun, B., Laskar, J., Hinnov, L. A., Thibault, N., Gardin, S., & Locklair, R. E. (2011). "Astronomical calibration of the Maastrichtian (late Cretaceous)". Earth and Planetary Science Letters 305 (3): 328–340. doi:10.1016/j.epsl.2011.03.008. 
  2. ^ a b Pearson, D. A., Schaefer, T., Johnson, K. R., Nichols, D. J., & Hunter, J. P. (2002). Vertebrate biostratigraphy of the Hell Creek formation in southwestern North Dakota and northwestern South Dakota. Hartman et al, 145-167.
  3. ^ Johnson, K. R., Nichols, D. J., & Hartman, J. H. (2002). Hell Creek Formation: A 2001 synthesis. The Hell Creek Formation and the Cretaceous-Tertiary Boundary in the northern Great Plains: Geological Society of America Special Paper, 361, 503-510.
  4. ^ Lofgren, D.F. (1997). "Hell Creek Formation". In: Currie, P.J. & Padian, K. (eds.). The Encyclopedia of Dinosaurs. San Diego: Academic Press. pp. 302–303. ISBN 978-0-122-26810-6.  Check date values in: |date= (help)
  5. ^ Cite error: The named reference breithaupt1997 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference eberth1997 was invoked but never defined (see the help page).
  7. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd Pearson et al. (2002) p. 154
  8. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar Pearson et al. (2002) pp. 145–167
  9. ^ a b c d e f g h i j k l m n o p q r s t u v Pearson et al. (2002) p. 155
  10. ^ a b c d e f g h i j k l m n o p q r s t u Pearson et al. (2002) pp. 156
  11. ^ Listed as "cf. Barbourula sp." in "Class Amphibia," Estes and Berberian, (1970). Page 4.
  12. ^ a b c d e f g h i j k l m n o p "Class Amphibia," in Estes and Berberian, (1970). Page 4.
  13. ^ a b c d e f g h i "Class Amphibia," in Estes and Berberian, (1970). Page 4. All taxa listed occur in Montana, see page 1.
  14. ^ Listed as "Eopelobates? sp." in "Class Amphibia," Estes and Berberian, (1970). Page 4.
  15. ^ a b c d David G. Demar Jr. (2013). "A new fossil salamander (Caudata, Proteidae) from the Upper Cretaceous (Maastrichtian) Hell Creek Formation, Montana, U.S.A.". Journal of Vertebrate Paleontology 33 (3): 588–598. doi:10.1080/02724634.2013.734887. 
  16. ^ a b c d e f g h i j k l m n o p "Class Osteichthyes," in Estes and Berberian, (1970). Page 3.
  17. ^ a b c d e f g h "Class Osteichthyes," in Estes and Berberian, (1970). Page 3. All taxa listed occur in Montana, see page 1.
  18. ^ a b c d "Class Osteichthyes," in Estes and Berberian, (1970). Page 4.
  19. ^ a b c "Class Osteichthyes," in Estes and Berberian, (1970). Page 4. All taxa listed occur in Montana, see page 1.
  20. ^ a b Listed as "cf. Paralbula casei" in "Class Osteichthyes," Estes and Berberian, (1970). Page 4.
  21. ^ a b c d e f g h i j k l m n o p q r s t u v w x y Todd D. Cook, Michael G. Newbrey, Donald B. Brinkman and James I. Kirkland (2014). "Euselachians from the freshwater deposits of the Hell Creek Formation of Montana". GSA Special Papers 503: 229–246. doi:10.1130/2014.2503(08). 
  22. ^ a b c d "Class Chondrichthyes," in Estes and Berberian, (1970). Page 3.
  23. ^ a b "Class Chondrichthyes," in Estes and Berberian, (1970). Page 3. All taxa listed occur in Montana, see page 1.
  24. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw "Dinosaur distribution (Late Cretaceous; North America; Montana)." Weishampel, et al. (2004). Page 584.
  25. ^ a b c d e f g h i j k l "Dinosaur distribution (Late Cretaceous; North America; South Dakota)." Weishampel, et al. (2004). Page 586.
  26. ^ a b c d "Dinosaur distribution (Late Cretaceous; North America; North Dakota)." Weishampel, et al. (2004). Page 585.
  27. ^ a b c d Bakker et al. (2006)
  28. ^ "Table 21.1," in Weishampel, et al. (2004). Page 465.
  29. ^ Nicholas R. Longrich (2011). "Titanoceratops ouranous, a giant horned dinosaur from the Late Campanian of New Mexico". Cretaceous Research 32. doi:10.1016/j.cretres.2010.12.007. 
  30. ^ Scannella, J. and Horner, J.R. (2010). "Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny." Journal of Vertebrate Paleontology, 30(4): 1157 - 1168. doi:10.1080/02724634.2010.483632
  31. ^ a b Campione, N.E. and Evans, D.C. (2011). "Cranial Growth and Variation in Edmontosaurs (Dinosauria: Hadrosauridae): Implications for Latest Cretaceous Megaherbivore Diversity in North America." PLoS ONE, 6(9): e25186. doi:10.1371/journal.pone.0025186
  32. ^ a b Listed as "?Thescelosaurus garbanii" in "Dinosaur distribution (Late Cretaceous; North America; Montana)." Weishampel, et al. (2004). Page 584.
  33. ^ Noted as being present, although misspelled as "Thescelosaurus garbani, in " "Dinosaur distribution (Late Cretaceous; North America; South Dakota)." Weishampel, et al. (2004). Page 586.
  34. ^ Boyd, Brown, et al. (2009)
  35. ^ Hutchinson and Chiappe, 1998. The first known alvarezsaurid (Theropoda: Aves) from North America. Journal of Vertebrate Paleontology. 18(3), 447–450.
  36. ^ Triebold, 1997. The Sandy Site: Small Dinosaurs from the Hell Creek Formation of South Dakota. in Wolberg, Stump and Rosenberg (eds). Dinofest International: Proceedings of a Symposium sponsored by Arizona
  37. ^ Listed as "?Ornithomimus sp." in "Dinosaur distribution (Late Cretaceous; North America; North Dakota)." Weishampel, et al. (2004). Page 585.
  38. ^ a b Longrich (2008), pages 983-996.
  39. ^ a b c d e f Lamanna, M. C.; Sues, H. D.; Schachner, E. R.; Lyson, T. R. (2014). "A New Large-Bodied Oviraptorosaurian Theropod Dinosaur from the Latest Cretaceous of Western North America". PLoS ONE 9 (3): e92022. doi:10.1371/journal.pone.0092022.  edit
  40. ^ a b c d e f Evans, D. C.; Larson, D. W.; Currie, P. J. (2013). "A new dromaeosaurid (Dinosauria: Theropoda) with Asian affinities from the latest Cretaceous of North America". Naturwissenschaften. doi:10.1007/s00114-013-1107-5.  edit
  41. ^ a b c d e f g h Larry D. Martin, Evgeny N. Kurochkin and Tim T. Tokaryk (2012). "A new evolutionary lineage of diving birds from the Late Cretaceous of North America and Asia". Palaeoworld 21. doi:10.1016/j.palwor.2012.02.005. 
  42. ^ Cite error: The named reference Potamornis was invoked but never defined (see the help page).
  43. ^ a b c d e f g h i j Longrich, N.R., Tokaryk, T. and Field, D.J. (2011). "Mass extinction of birds at the Cretaceous–Paleogene (K–Pg) boundary." Proceedings of the National Academy of Sciences, 108(37): 15253-15257. doi:10.1073/pnas.1110395108
  44. ^ a b "Class Aves," in Estes and Berberian, (1970). Page 7.
  45. ^ "Class Aves," in Estes and Berberian, (1970). Page 7. All taxa listed occur in Montana, see page 1.
  46. ^ a b Henderson and Peterson (2006) 192–195.
  47. ^ a b c d e f g h R. Matsumoto, S. E. Evans (2010). "Choristoderes and the freshwater assemblages of Laurasia". Journal of Iberian Geology 36 (2): 253–274. doi:10.5209/rev_jige.2010.v36.n2.11. 
  48. ^ a b c d e f g h "Order Testudinata," in Estes and Berberian, (1970). Page 5.
  49. ^ a b c d "Order Testudinata," in Estes and Berberian, (1970). Page 5. All taxa listed occur in Montana, see page 1.
  50. ^ a b c d e Georgia E. Knauss, Walter G. Joyce, Tyler R. Lyson and Dean Pearson (2011). "A new kinosternoid from the Late Cretaceous Hell Creek Formation of North Dakota and Montana and the origin of the Dermatemys mawii lineage". Paläontologische Zeitschrift 85 (2): 124–142. doi:10.1007/s12542-010-0081-x. 
  51. ^ a b c d e f g h i j k l m n o p Nicholas R. Longrich, Bhart-Anjan S. Bhullar and Jacques A. Gauthier (2012). "Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary". Proceedings of the National Academy of Sciences of the United States of America 109 (52): 21396–21401. doi:10.1073/pnas.1211526110. PMC 3535637. PMID 23236177. 
  52. ^ a b c d e f Nicholas R. Longrich, Bhart-Anjan S. Bhullar and Jacques A. Gauthier (2013). "Correction for "Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary," by Nicholas R. Longrich, Bhart-Anjan S. Bhullar, and Jacques A. Gauthier, which appeared in issue 52, December 26, 2012, of Proc Natl Acad Sci USA (109:21396–21401; first published December 10, 2012; 10.1073/pnas.1211526110)". Proceedings of the National Academy of Sciences of the United States of America 110 (16): 6608. doi:10.1073/pnas.1303907110. 
  53. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd be bf bg bh bi bj bk bl bm bn bo bp bq br bs bt bu bv bw bx by bz ca cb cc cd ce cf cg ch ci cj ck cl cm cn co cp Zofia Kielan-Jaworowska, Richard L. Cifelli, and Zhe-Xi Luo, Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure, Columbia University Press, New York, 2004 ISBN 0-231-11918-6, p. 98-99
  54. ^ a b c d e Gregory P. Wilson (2013). "Mammals across the K/Pg boundary in northeastern Montana, U.S.A.: dental morphology and body-size patterns reveal extinction selectivity and immigrant-fueled ecospace filling". Paleobiology 39 (3): 429–469. doi:10.1666/12041. 
  55. ^ a b c d e f g J. David Archibald, Yue Zhang, Tony Harper and Richard L. Cifelli (2011). "Protungulatum, confirmed Cretaceous occurrence of an otherwise Paleocene eutherian (placental?) mammal". Journal of Mammalian Evolution 18 (3): 153–161. doi:10.1007/s10914-011-9162-1. 
  56. ^ Thomas E. Williamson, Stephen L. Brusatte, Thomas D. Carr, Anne Weil and Barbara R. Standhardt (2012). "The phylogeny and evolution of Cretaceous–Palaeogene metatherians: cladistic analysis and description of new early Palaeocene specimens from the Nacimiento Formation, New Mexico". Journal of Systematic Palaeontology 10 (4): 625–651. doi:10.1080/14772019.2011.631592. 
  57. ^ Chandrasekharam, A., 1974. Megafossil flora from the Genesee locality, Alberta, Canada. Palaeontographica, Abt. A, Band 174, 41 p.
  58. ^ Christophel, D.C., 1976. Fossil floras from the Smoky Tower locality, Alberta, Canada. Palaeontographica, Abt. B, Band 157, 43 p.

References[edit]

  • Pearson, D.A.; Schaefer, T.; Johnson, K.R.; Nichols, D.J.; Hunter, J.P. (2002). "Vertebrate Biostratigraphy of the Hell Creek Formation in Southwestern North Dakota and Northwestern South Dakota". In Hartman, John H.; Johnson, Kirk R.; Nichols, Douglas J.. "The Hell Creek Formation and the Cretaceous-Tertiary boundary in the northern Great Plains: An integrated continental record of the end of the Cretaceous". Geological Society of America Special Paper (Boulder, Colorado) 361: 145–167. 
  • Bakker, R. T., Sullivan, R. M., Porter, V., Larson, P. and Saulsbury, S.J. (2006). "Dracorex hogwartsia, n. gen., n. sp., a spiked, flat-headed pachycephalosaurid dinosaur from the Upper Cretaceous Hell Creek Formation of South Dakota." in Lucas, S. G. and Sullivan, R. M., eds., Late Cretaceous vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35, pp. 331–345. [1]
  • Boyd, Clint A.; Brown, Caleb M.; Scheetz, Rodney D.; Clarke; Julia A. (2009). "Taxonomic revision of the basal neornithischian taxa Thescelosaurus and Bugenasaura". Journal of Vertebrate Paleontology 29 (3): 758–770. doi:10.1671/039.029.0328. 
  • Estes, R., and P. Berberian. 1970. Paleoecology of a late Cretaceous vertebrate community from Montana. Breviora volume 343, 35 pages.
  • 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.
  • 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.
  • Varricchio, D. J. 2001. Late Cretaceous oviraptorosaur (Theropoda) dinosaurs from Montana. pp. 42–57 in D. H. Tanke and K. Carpenter (eds.), Mesozoic Vertebrate Life. Indiana University Press, Indianapolis, Indiana.
  • Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.

External links[edit]