Paleobiota of the Hell Creek Formation

Fossil flora and fauna of North American site

This is an overview of the fossil flora and fauna of the Maastrichtian-Danian Hell Creek Formation.

## Invertebrates

[edit]

### Insects

[edit]

Insects from the groups Diptera, Zygoptera, and possibly Hemiphlebiidae have been unearthed in Hell Creek in amber.[1][2] Fossils found in the Hell Creek Formation and the Fort Union Formation of these insects went extinct during the K-T Event.[3][4][5]

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Color key
| Taxon | Reclassified taxon | Taxon falsely reported as present | Dubious taxon or junior synonym | Ichnotaxon | Ootaxon | Morphotaxon

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| Notes
Uncertain or tentative taxa are in small text; ~~crossed out~~ taxa are discredited.
Genus  | Species  | Location  | Stratigraphic position  | Material  | Notes  | Images

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Cephaloleichnites

Cephaloleichnites strongi

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Possible hispine beetle herbivory on Zingiberopsis attenuta

?Hemiphlebiidae[2]

Indeterminate

|  |  |  |

Possible Hemiphlebiid damselflies

Brachycera[1]

Indeterminate

|  |  |  |

Undescribed brachyceran flies

Nematocera[1]

Indeterminate

|  |  |  |

Undescribed nematoceran flies

Aeschnidiidae[6]

Indeterminate

|  |  |  |

Indeterminate aeschnidiid dragonflies

### Molluscs

[edit]

Genus  | Species  | Location  | Stratigraphic position  | Material  | Notes  | Images

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Plesielliptio |

P. postbiplicatus

|  |  |  |

Freshwater Unionid river mussels

P. gibbosoides

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Freshwater Unionid river mussels

P. whitfieldi

|  |  |  |

Freshwater Unionid river mussels

Rhabdotophorus | R. aldrichi |  |  |  | Freshwater mussel of family Unionidae.[7] |
Pleurobema | P. cryptorhynchus |  |  |  | Freshwater mussel of family Unionidae.[7] |
Plethobasus | P. aesopiformis |  |  |  | Freshwater mussel of family Unionidae.[7] |
P. biesopoides |  |  |  |  |
Quadrula | Q. cylindricoides |  |  |  | Freshwater mussel of family Unionidae.[7] |
Proparreysia | P. verrucosiformis |  |  |  | Freshwater mussel of family Unionidae.[7] |
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 | South Dakota  |  |  | From a marine facies ("tongue"). Modern members of the genus live in fresh water  |
Sphaerium | S. beckmani |  |  |  | "Pill clam". "Nut clam". "Fingernail clam". "Pea clam". Family Sphaeriidae.  |
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 (cockle). 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.  |

## Amphibians

[edit]

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Color key
| Taxon | Reclassified taxon | Taxon falsely reported as present | Dubious taxon or junior synonym | Ichnotaxon | Ootaxon | Morphotaxon

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| Notes
Uncertain or tentative taxa are in small text; ~~crossed out~~ taxa are discredited.
Genus  | Species  | Location  | Stratigraphic position  | Material  | Notes  | Images

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Anura (frog)[8]

indeterminate[8]

* North Dakota[9]
* South Dakota[9]

Middle to upper Hell Creek Formation[10]

3 unassigned specimens[11]

Anura indet. consists of material not currently assigned to any genus of frog.[8]

Barbourula[12]

Indeterminate[13]

* Montana[14]

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Caudata (salamander)[8]

indeterminate[8]

* North Dakota[9]
* South Dakota[9]

Lower to uppermost Hell Creek Formation[10]

149 unassigned specimens[11]

Material of Caudata indet. is not currently assigned to any genus.[8]

Eopelobates[15]

Indeterminate[13]

* Montana[14]

|  |  |  |

Habrosaurus[8][13]

H. dilatus[8][13]

* Montana[14]
* North Dakota[9]
* South Dakota[9]

Middle to upper Hell Creek Formation[10]

6 specimens[11]

Habrosaurus is a sirenid amphibian.[8]

Lisserpeton[13]

L. bairdi[13]

* Montana[14]

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Opisthotriton[8][13]

O. kayi[8][13]

* Montana[14]
* North Dakota[9]
* South Dakota[9]

Lower to upper Hell Creek Formation[10]

22 specimens[11]

Opisthotriton is classified as a Batrachosauroididae.[8]

Paranecturus[16]

P. garbanii[16]

* Montana[16]

|  |  |

A member of Proteidae.[16]

Proamphiuma[13]

P. cretacica[13]

* Montana[14]

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Prodesmodon[13]

P. copei[13]

* Montana[14]

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Scapherpeton[8][13]

S. tectum[8][13]

* Montana[14]
* North Dakota[9]
* South Dakota[9]

Lower to upper Hell Creek Formation[10]

144 specimens[11]

Scapherpeton is a scapherpetonid that is very common in the Hell Creek Formation.[8]

Scotiophryne[13]

S. pustulosa[13]

* Montana[14]

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A small frog

## Fish

[edit]

### Bony fish

[edit]

Bony fishes

Genus | Species | Location | Stratigraphic position | Material | Notes | Images
Acipenser[8][17][18] | A. amnisinferos[18] |

* North Dakota (Tanis)[18]

|  |  | A sturgeon |
A. eruciferus[17] |

* Montana[19]

|  |  |
A. praeparatorum[18] |

* North Dakota (Tanis)[18]

|  |  |
A. cf. A. amnisinferos[18] |

* North Dakota (Tanis)[18]

|  |  |

cf. A. sp.[8]

* North Dakota[9]
* South Dakota[9]

Lower to upper Hell Creek Formation[10]

18 specimens are tentatively assigned to Acipenser sp.[11]

Acipenser sp. is tentatively referred to the genus.[8]

Anchiacipencer[20] | A. acanthaspis[20] |

* Montana[20]

|  |  | A sturgeon, originally considered as indeterminate material[20] |
Belonostomus[8][17] | B. longirostris[8][17] |

* Montana[19]
* North Dakota[9]
* South Dakota[9]

| Lower to upper Hell Creek Formation[10] | 28 specimens[11] | A long-snouted slender fish classified as an aspidorhynchid.[8] |
Coriops[21] | C. amnicolus[21] |

* Montana[22]

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Cyclurus[17]

C. fragosus[17]

* Montana[19]
* North Dakota[9]
* South Dakota[9]

|  |  | A small amiid fish (ubiquitous). Previously known as Amia fragosa or Kindleia fragosa.[23] 2610 specimens have been assigned to Kindleia, making it an extremely common genus.[11] | Cyclurus kehreri from Messel Pit, species within same genus as C. fragosus
"Lepisosteus"[8][17] | "L. occidentalis"[8][17] |

* Montana[19]
* North Dakota[9]
* South Dakota[9]

| Lower to uppermost Hell Creek Formation[10] | 938 specimens are assigned to Lepidosteus[11] | A lepidosteid that is very common in the Hell Creek Formation.[8] Nomen dubium.[24] |
Melvius[8] | M. thomasi[8] |

* North Dakota[9]
* South Dakota[9]

| Lower to upper Hell Creek Formation[10] | 6 specimens are assigned to Melvius[11] | A large amiid fish.[8] |
Phyllodus | P. paulkatoi |  |  |  | Fish with columnar teeth  |
Palaeolabrus[17] | P. montanensis[17] |

* Montana[19]

|  |  |  |
Paleopsephurus[17] | P. wilsoni[17] |

* Montana[19]

|  |  | A paddlefish |
Paralbula[25] | P. casei[25] |

* Montana[22]

|  |  |  |
Parapsephurus[26] | P. willybemisi[26] |

* North Dakota (Tanis)[26]

|  |  | A paddlefish  |
Platacodon[21] | P. nanus[21] |

* Montana[22]

|  |  | Small teleost fish |
Protamia[17] | Indeterminate[17] |

* Montana[19]

|  |  |  |
Pachyrhizodontoidei | Indeterminate  |  |  |  | Fish  |
Polyodontidae[27] | Indeterminate[27] |

* Montana[27]

|  |  | Paddlefish  |
Protoscaphirhynchus[17] | P. squamosus[17] |

* Montana[19]

|  |  | A sturgeon  |
Pugiopsephurus[26] | P. inundatus[26] |

* North Dakota (Tanis)[26]

|  |  | A paddlefish  |

### Cartilaginous fish

[edit]

Chondrichthyes reported from the Hell Creek Formation

Genus  | Species  | Location  | Stratigraphic position  | Material  | Notes  | Images

Chiloscyllium[28]

C. sp.[28]

* Montana[28]

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A member of Hemiscylliidae.[28]

Galagadon[29]

G. nordquistae

* South Dakota

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Isolated teeth

A carpet shark

Lonchidion[30]

L. selachos[30]

* Montana[31]
* North Dakota[9]
* South Dakota[9]

Lower to upper Hell Creek Formation[10]

40 specimens[11]

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.[8]

Myledaphus[28]

M. pustulosus[28]

* Montana[28]
* North Dakota[9]
* South Dakota[9]

Lower to upper Hell Creek Formation.[10]

1677 specimens[11] previously assigned to M. bipartitus.[28]

Is an anacoracid batoid[8] rajiform related to guitarfishes.[28] Described on the basis of teeth formerly assigned to the species M. bipartitus.[28] The material assigned to Myledaphus bipartitus and makes up 16.5% of the vertebrate remains.[8]

Protoginglymostoma[28]

P. estesi[28]

* Montana[28]

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A member of Ginglymostomatidae.[28] Formerly assigned to the genus Brachaelurus.

Restesia[28]

R. americana[28]

* Montana[28]
* North Dakota[9]
* South Dakota[9]

Middle Hell Creek Formation[10]

5 specimens previously assigned to Squatirhina[11]

A wobbegong-like shark.[28] Formerly assigned to Squatirhina. The remains consist of 0.05% of the vertebrates.[11] Also known from the Lance Formation.[28]

Carcharhinidae indet.[29]

Indeterminate

* South Dakota

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An isolated tooth.

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Scapanorhynchus[32]

.sp.

* North Dakota

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## 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.[33]

* Ceratopsidae 61%
* Hadrosauridae 23%
* Ornithomimidae 5%
* Tyrannosauridae 4%
* Hypsilophodontidae 3%
* Dromaeosauridae 2%
* Pachycephalosauridae 1%
* Ankylosauridae 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. Other dinosaurs, such as Sphaerotholus, Denversaurus, Torosaurus, Struthiomimus, Acheroraptor, Dakotaraptor, Pectinodon, Richardoestesia, Paronychodon, Anzu, Leptorhynchos and Troodon (more likely Pectinodon), 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.

Fossil footprints of dinosaurs from the Hell Creek Formation are very rare. As of 2017, there is only one find of a possible Tyrannosaurus rex footprint, dating from 2007 and described a year later.[34] A trackway made by mid-sized theropod, possibly a small tyrannosaurid individual, was discovered in South Dakota in 1997, and in 2014 these footprints were named Wakinyantanka styxi.[35]

### Ornithischians

[edit]

#### Ankylosaurs

[edit]

Indeterminate nodosaur remains have been unearthed in the Hell Creek Formation and other nearby areas.[36][37]

Ankylosauria reported from the Hell Creek Formation

Genus  | Species  | State  | Stratigraphic position  | Material  | Notes  | Images

Ankylosaurus[38]

A. magniventris[38]

* Montana[38]

* Upper

| A partial skull, teeth, cervical vertebrae, dorsal vertebrae, caudal vertebrae, right scapulocoracoid, otic capsule, maxilla fragment, right jugal, left jugal and quadratojugal, sacral centra, additional fragments of the cervical half rings and a partial tail club handle.  |

An ankylosaur. Also found in the Lance, Frenchman, Ferris and Scollard Formations.

Denversaurus[39]

| D. schlessmani[39] |

* South Dakota[36]

* Lower[36]

| A complete skull without the lower jaw and associated plates (DMNH 468)[36] | A nodosaurid ankylosaur whose remains have been also found in the Lance Formation[40] |

#### Pachycephalosaurs

[edit]

An undescribed and unnamed pachycephalosaur is present in North Dakota.[41] Pachycephalosaur remains have been unearthed in Montana as in the case of Platytholus and the now invalid genus Stenotholus kohleri, which is now a junior synonym of Pachycephalosaurus.[42] Dracorex hogwartsia is agreed by paleontologists to be an ontogimorph of either Pachycephalosaurus or Stygimoloch, while the synonymy of Stygimoloch spinifer with Pachycephlosaurus remains uncertain due to difference in stratigraphic level.[43][44][45]

Pachycephalosaurs reported from the Hell Creek Formation

Genus  | Species  | State  | Stratigraphic position  | Material  | Notes  | Images

Pachycephalosaurus[38]

P. wyomingensis[38]

* Montana[38]
* South Dakota[46]

|  |  |

A pachycephalosaur. Also found in the Lance Formation.

Platytholus[47] | P. clemensi[47] |

* Montana[47]

* Lower[47]

| A partial skull[47] | A medium-sized pachycephalosaurine closely related to Acrotholus and Prenocephale |

Sphaerotholus[38]

S. buchholtzae[38]

* Montana[38]

* Lower to upper[48][49]

"Skull material."[50]

A pachycephalosaur whose remains have also been found in the Frenchman Formation. Genus also known from the Kirtland Formation, Dinosaur Park Formation and the Horseshoe Canyon Formation.

S. triregnum[49]

* Montana[49]

* Middle[49]

A left squamosal.[49]

A pachycephalosaur distinguished from S. buchholtzae by its more ornamented squamosal.[49]

Stygimoloch[38]

S. spinifer[38]

* Montana[38]
* South Dakota
* North Dakota

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

#### Ceratopsians

[edit]

Indeterminate ceratopsid teeth and some identifiable bones from Triceratops can be extremely common.[51][52][53][54][55] 8.31% of all vertebrate remains from the Hell Creek Formation are unassigned ceratopsids.[11] In 2012, a new unidentified species of chasmosaur ceratopsian with noticeable differences from Triceratops was unearthed in South Dakota by a fossil hunter named John Carter.[56][57][58]

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Color key
| Taxon | Reclassified taxon | Taxon falsely reported as present | Dubious taxon or junior synonym | Ichnotaxon | Ootaxon | Morphotaxon

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| 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[38]

L. gracilis[38]

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* Montana[38]

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A small primitive-looking ceratopsian. Fossils have also been found in the Lance Formation in Wyoming.[59]

Tatankaceratops[60]

T. sacrisonorum[60]

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* South Dakota[60]

|  |  |

A controversial ceratopsian possibly synonymous with Triceratops[61]

Torosaurus[8][38]

T. latus[8][38]

|  |

* Montana[38]
* North Dakota[9][41]
* South Dakota[9][46]

Upper Hell Creek Formation[10]

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A ceratopsian that was once proposed to be synonymous with Triceratops,[62] but is now regarded as a valid and distinct ceratopsian.[63] A rare ceratopsid.[10] Fossils have been in the Lance Formation, Javelina Formation, North Horn Formation, Laramie Formation, El Picacho Formation, Frenchman Formation and Scollard Formation.

Triceratops[8][38]

T. horridus[8][38]

* T. serratus[38]
* Ugrosaurus olsoni[64]

* Montana[38]
* North Dakota[9][41]
* Wyoming
* South Dakota[9][46]

Lowermost to the middle Hell Creek Formation[65]

Four specimens are assigned to Triceratops horridus from the Hell Creek Formation.[11] Isolated, shed ceratopsid teeth are incredibly common in the Hell Creek and Lance Formations, being by most collectors, with some being nothing more than worn down fragments up to superb teeth containing complete, preserved roots. Because the teeth of different ceratopsians are so similar to one another, its hard to differentiate between genera/species, but based on the abundance of identifiable bones belonging to Triceratops in Lancian-aged North American formations, especially the Hell Creek, isolated ceratopsid teeth from the lower and middle Hell Creek Formation have a high likelihood of originating from T. horridus.

A ceratopsian.[8] Also found in the Evanston, Frenchman, Lance, Laramie, and Scollard Formations.

T. prorsus[38]

|  |

* Montana[38]
* South Dakota

| Upper 1/3 of the Hell Creek Formation[65] |

Very common.[citation needed] Because the teeth of different ceratopsians are so similar to one another, its hard to differentiate between genera/species, but based on the abundance of identifiable bones belonging to Triceratops in Lancian-aged North American formations, especially the Hell Creek, isolated ceratopsid teeth from the upper 1/3 of the Hell Creek Formation have a high likelihood of originating from T. prorsus.

Also found in the Frenchman and Lance Formations.

#### Ornithopods and relatives

[edit]

Indeterminate hadrosaurid remains are very common in the Hell Creek Formation.[8] Fossils of indeterminate lambeosaurs have been unearthed in Hell Creek, specifically in South Dakota and Montana.[66][67][68][69][70][71]

Ornithopods and Thescelosaurs reported from the Hell Creek Formation

Genus  | Species  | Synonyms  | State  | Stratigraphic position  | Material  | Notes  | Images

Edmontosaurus

E. annectens

* Anatosaurus annectens[72]
* Anatotitan copei[72]

* Montana[38]
* South Dakota[46]
* North Dakota(Mummy Fossil)[73][74]

|  |

Very common.

A hadrosaur. Also found in the Denver, Frenchman, Lance, Laramie, and Scollard Formations.[75][76] Hatchlings have also been unearthed.[76]

Thescelosaurus[46]

T. garbanii[77][78]

* Bugenasaura garbanii[78]

* Montana[77]
* South Dakota[79]

|  |  |  |

T. neglectus[8][46]

|  |

* North Dakota[9]
* South Dakota[9][46]

Lower to upper Hell Creek Formation[10]

50 specimens[11]

A small thescelosaurine. Also found in the Frenchman, Lance, Laramie, and Scollard Formations.[80] Two species are known from Hell Creek; T. neglectus and T. garbanii.[81]

### Theropods

[edit]

Theropod tracks have been found in South Dakota.[46] A trackway from South Dakota, named Wakinyantanka, was made by a mid-sized theropod with three slender toes, possibly a small tyrannosaurid.[35] A second footprint that may have been made by a specimen of Tyrannosaurus was first reported in 2007 by British paleontologist Phil Manning, from the Hell Creek Formation of Montana.[82] This second track measures 72 centimeters (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 is the only large theropod known to have existed in the Hell Creek Formation, though in past albertosaurine remains have described here but its most likely that they are the remains of Tyrannosaurus rex.[83][84] Theropod remains are very common in Hell Creek, some of which belong to indeterminate species on maniraptorans.[85]

#### Alvarezsaurs

[edit]

Alvarezsaurs reported from the Hell Creek Formation

Genus  | Species  | Synonyms  | State  | Stratigraphic position  | Material  | Notes  | Images
"Ornithomimus" | "O." minutus |  |  |  |  |  |

Trierarchuncus[86]

T. prairiensis[86]

|  |

* Montana[38]

upper Hell Creek Formation.

|  |

An alvarezsaur known from a partial post-cranial skeleton.[87]

#### Tyrannosaurids

[edit]

Tyrannosaurids reported from the Hell Creek Formation

Genus  | Species  | Synonyms  | State  | Stratigraphic position  | Material  | Notes  | Images

Tyrannosaurus[8][38]

T. rex[8][38]

* Albertosaurus megagracilis[38]
* Aublysodon molnari[38]
* Dinotyrannus megagracilis[38]
* Nanotyrannus lancensis?

* Montana[38]
* North Dakota[9][41]
* South Dakota[9][46]

Lower to upper Hell Creek Formation.

|  |

A tyrannosaur, known from several specimens including a juvenile nicknamed "Jane".[88] Also found in the Denver, Frenchman, Hill Creek South, Javelina, Lance, Ferris, Livingston, McRae, North Horn, Scollard, Willow Creek Formation, and also found in Lomas Coloradas Formations. Isolated teeth in the Hell Creek are common enough to be dug commercially by collectors, but rare enough that they are often sold for very high prices with fragmentary teeth usually beginning at least in the hundreds of USD, and complete teeth in the thousands of USD. Perhaps the best known iconic dinosaur.

Nanotyrannus?[8][38]

N.lancensis[8][38]

* Stygivenator?
* Deinodon lancensis
* Albertosaurus lancensis[38]
* Tyrannosaurus lancensis?

* Montana
* Wyoming

Lower to upper Hell Creek Formation.

A few specimens are known

Invalid genus, now recognised as juvenile T. rex.

#### Ornithomimosaurs

[edit]

Ornithomimid remains are not uncommon in the Hell Creek Formation.[8] Fifteen specimens from the Hell Creek Formation are undetermined ornithomimids[11]

|  |

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Color key
| Taxon | Reclassified taxon | Taxon falsely reported as present | Dubious taxon or junior synonym | Ichnotaxon | Ootaxon | Morphotaxon

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|
|
|

| 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

* South Dakota[89]

|  |

One partial skeleton.

An ornithomimid; nomen nudum.

Struthiomimus[46]

S. sedens[90]

* Montana

|  |

* AMNH 975, a foot claw
* UCMP 154569, a partial skeleton

A large ornithomimid similar to Gallimimus in size. Also found in the Lance Formation.[90]

Ornithomimus

O. velox[90]

* Montana
* South Dakota
* North Dakota

|  |

Fragmentary specimens

An ornithomimid which was also found in the Denver Formation.

#### Oviraptorosaurs

[edit]

Oviraptorosaur fossils have been found at the Hell Creek Formation for many years, most notably from isolated elements until the discovery of Anzu. In the past, oviraptorosaur fossils found were thought to have belonged to Leptorhynchos, Caenagnathus, Chirostenotes, and Elmisaurus.[38][91][92][93][94][95] In 2016, an undescribed large-bodied caenagnathid was unearthed in Montana.[96]

|  |

|
|

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[38][91]

A. wyliei[91]

* North Dakota[9][91]
* South Dakota[9][91]

Lower to upper Hell Creek Formation[11]

12 well-preserved specimens[10]

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.[91]

Caenagnathidae

Indeterminate

* Montana

|  |  |

Similar to Citipes and Elmisaurus.

Eoneophron | E. infernalis |

* South Dakota[97]

|  | A partial right hindlimb[97] | Closely related to Citipes and Elmisaurus.[97] |

#### Eumaniraptorans

[edit]

Historically, numerous teeth have been attributed to various dromaeosaurid and troodontid taxa with known body fossils from only older formations, including Saurornithoides, Zapsalis, Dromaeosaurus, Saurornitholestes, and Troodon. 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. This was seemingly disproven in 2015, when DePalma et al., described the new genus Dakotaraptor, a large species of dromaeosaur.[98] However, Dakotaraptor’s validity has been called into question since, as the holotype may be a chimeric assemblage of various non-dromaeosaurid coelurosaurians.[99] Fossilized teeth of various troodontids and coelurosaurs are common throughout the Hell Creek Formation; the best known examples include Paronychodon, Pectinodon and Richardoestesia, respectively. Teeth belonging to possible intermediate species of Dromaeosaurus[100] and Saurornitholestes[101] have been unearthed at the Hell Creek Formation and the nearby Lance Formation.

Eumaniraptorans reported from the Hell Creek Formation

Genus  | Species  | State  | Stratigraphic position  | Material  | Notes  | Images

Acheroraptor[98]

A. temertyorum [98]

* Montana[98]
* North Dakota?[8]
* South Dakota?[8]

Lower? to upper Hell Creek Formation[8]

* ROM 63777, a maxilla and tooth[98]
* ROM 63778, a partial dentary[98]
* isolated teeth[98]

A velociraptorine dromaeosaurid. Teeth previously referred to various 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 the former two taxa being present in the Hell Creek-Lance assemblages.[98]

Avisaurus[8]

A. archibaldi[8][38]

* Montana[8]

Middle Hell Creek Formation[10]

* UCMP 117600, holotype, a tarsometatarsus
* PU 17324, a tarsometatarsus

An avisaurid.[8]

cf. A. archibaldi[102]

* Montana[102]

Uppermost Hell Creek Formation[102]

* YPM 57235, a coracoid

An avisaurid tentatively referred to A. archibaldi based on its size.[102]

A. darwini[103] |

* Montana

|  |

* DDM 1577.730, a right tarsometatarsus

|  |

A. sp.[104]

* Montana[104]

|  |

* distal tarsals, metatarsus (juvenile)[104]
* MOR3070, a partial right tarsometatarsus

|  |

Brodavis[105]

B. baileyi[105]

* South Dakota[105]

|  |

* UNSM 50665, a left tarsometatarsus missing proximal end, trochleae II and III.[105]

A primitive hesperornithiform.[105]

Dakotaraptor[106]

D. steini [106]

* South Dakota[106]

Upper Hell Creek Formation[106]

* PBMNH.P.10.113.T, a partial skeleton.[106]
* PBMNH.P.10.115.T, a tibia.[106]
* PBMNH.P.10.118.T, an astragalocalcaneum.[106]
* isolated teeth.[106]

A large dromaeosaurid. Possibly chimeric.[98][99]

Magnusavis[103] | M. ekalakaensis |

* Montana

|  |

* CCM V2019.5.1, partial right tarsometatarsus and toe bone

| A large enantiornithine closely related to avisaurids.  |

Paronychodon[107]

P. caperatus[107]

* North Dakota, South Dakota, and Montana.

|  |

* YPM 10624, a fossilized tooth. Teeth of this genus have been found too.

A troodontid theropod who is known from fossil teeth. Fossils have also been found in the Lance Formation in Wyoming.

Pectinodon[108][107]

P. bakkeri[108][107]

* Montana

|  |

* UCM 38445, a fossilized tooth. Teeth of this genus have been found too.

* A troodontid theropod who is known from fossil teeth. Fossils have also been found in the Lance Formation in Wyoming.

Potamornis[105] |

P. skutchi [109]

* Montana[109]

|  |

* UCMP 117605, a tarsometatarsus

A hesperornithiform also found in the Lance Formation.[109]

Richardoestesia[110][111]

R. sp.[110][111]

* Montana.

|  |

* Teeth.

A coelurosaur that is known from teeth and from two species Richardoestesia gilmorei and Richardestesia isosceles, which have also been unearthed in the Lance Formation in Wyoming.

"Styginetta"[112] | "S. lofgreni."  |

* Montana.

|  |  | A Presbyornithid, it is notable for being one of the few birds known to have survived the Cretaceous–Paleogene extinction event.  |

"Unnamed enantiornithine B"[102]

Unnamed

* Montana[102]

|  |

* YPM 57823, a partial coracoid[102]

An unnamed enantiornithean.[102]

"Unnamed hesperornithiform A"[102]

Unnamed

* Montana

|  |

* UCMP 13355, a tarsometatarsus

A primitive hesperornithiform.[105] The Hell Creek specimen was referred to the same unnamed taxon as RSM P 2315.1 from the Canadian Frenchman Formation.[102] RSM P 2315.1 was later made the holotype of Brodavis americanus.[105] May be a synonym of Potamornis.[102]

"Unnamed ornithurine B"[102]

Unnamed[113]

* Montana[114]

|  |

* UCMP 129143, a partial coracoid[102]

An ornithurine possibly similar to Cimolopteryx[102][113]

"Unnamed ornithurine C"[102]

Unnamed

* Montana[102]
* South Dakota[102]

|  |

* SDSM 64281A, a partial coracoid[102]
* SDSM 64281B, a partial coracoid[102]
* UCMP 175251, a partial coracoid[102]
* MOR 2918, a partial coracoid[102]

An ornithurine, also present in the Lance Formation and Fort Union Formation, one of the few individual bird species known to have survived the Cretaceous–Paleogene extinction[102]

"Unnamed ornithurine D"[102]

Unnamed

* Montana[102]

|  |

* UCMP 187207, a partial coracoid[102]

An ichthyornithean also present in the Frenchman Formation[102]

## Pterosaurs

[edit]

Undescribed pterosaur remains were reported from North Dakota.[115] Undescribed pteranodontian specimen has also been mentioned in the supplementary material of Longrich et al. (2018).[116]

Pterosaurs of the Hell Creek Formation

Taxa  | Species  | State  | Stratigraphic location  | Material  | Notes  | Images

Infernodrakon[117]

I. hastacollis

| Montana[115] |  |  | A single azhdarchid neck bone originally considered to belong to the genus Quetzalcoatlus.[115] |

## 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[118]

* B. sternbergii[118]

* Montana
* North Dakota
* South Dakota

|  |  |

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

Brachychampsa[118]

* B. montana[118]

* Montana
* South Dakota
* North Dakota

|  |  |

Extinct genus of alligatoroid.

Thoracosaurus[118]

* T. neocesariensis[118]

* Montana

|  |  |

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

## 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[119]

Indeterminate[119]

* Montana[120]

|  |  |

Extinct genus of aquatic turtles belonging to the family Adocidae.

Axestemys[121]

A. infernalis[121]

* Montana
* North Dakota
* South Dakota
* Wyoming

|  |  |

A turtle belonging to the family Trionychidae. Its fossils from the Hell Creek Formation were formerly assigned to the late Campanian species Axestemys splendidus.[122][121]

Compsemys[119]

C. victa[119]

* Montana[120]

|  |  |

A relative of Dermatemydidae.

Peckemys

P. brinkman

* Montana
* North Dakota

|  |  |

A relative of Baenidae.

Emarginachelys

E. cretacea

* Montana

|  |  |

A relative of chelydrids.[123]

Eubaena[119]

E. cephalica[119]

* Montana[120]

|  |  |

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[123]

H. clark[123]

* North Dakota[123]

|  |  |

A kinosternoid related to the Central American river turtle.[123]

Hutchemys[124] | H. walkerorum[124] |

* North Dakota[124]

|  | A shell[124] | A Plastomeninae related to the softshell turtle.[124] |

Plastomenus

P. sp

|  |  |  |

Trionychidae turtle.

Basilemys

B. sinuosa

|  |  |  |

Largest dermatemydid land tortoise.

Trionyx[119]

Indeterminate[119]

* Montana[120]

|  |  |

A genus of softshell turtles belonging to the family Trionychidae.

Aspideretoides

A. foveatus

|  |  |  |

Trionychidae turtle.

Helopanoplia

H. distincta

|  |  |  |

Trionychidae turtle.

Judithemys

J. backmani

|  |  |  |

Thin-shelled macrobaenid turtle.

Plesiobaena

P. antiqua

|  |  |  |

Baenid turtle.

Stygiochelys

S. estesi

|  |  |  |

Baenid turtle.

Neurankylus

N. eximius

|  |  |  |

Largest baenid turtle in Hell Creek Formation.

Saxochelys[125]

S. gilberti

* North Dakota

|  |

* A population of over 30 individual skeletons

A member of the family Baenidae.

Thescelus

T. insiliens

|  |  |  |

Baenid turtle.

Chelydridae

Indeterminate

|  |  |  |

Chelydrids-like turtle.

## Squamata

[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[126][127] | C. monstrosus[126][127] | Montana[126] |  |  |

A platynotan lizard of uncertain phylogenetic placement, also known from the Lance Formation.[126]

Cerberophis[126][127] | C. robustus[126][127] | Montana[126] |  |  | An alethinophidian snake of uncertain phylogenetic placement.[126] |
Obamadon[126][127] | O. gracilis[126][127] | Montana[126] |  |  | A polyglyphanodontian lizard of uncertain phylogenetic placement. Also known from the Lance Formation.[126] |
Peneteius[126] | P. aquilonius[126] | Montana[126] |  |  | A chamopsiid polyglyphanodontian lizard.[126] |
Haptosphenus | H. placodon |  |  |  | Teiidae lizard.  |
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.  |
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.  |
Mosasaurinae | Indeterminate  | North Dakota  |  |  | Indeterminate mosasaurine remains have been unearthed in North Dakota; they may belong to a mosasaur measuring 11 m (36 ft) in length.[128][129] |

## 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[130]

* C. ambulator[130]
* C. laramiensis[130]

* Montana[130]

|  |  |

A champsosaur. Indeterminate species also known from North Dakota.[118]

## 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[131]

C. minor[131]

* Montana[131]

|  |  |

A multituberculate of uncertain phylogenetic placement.

Cimolodon[131]

C. nitidus

* Montana
* North Dakota[131]

|  |  |

A cimolodontid multituberculate.

C. cf. nitidus[131]

* South Dakota[131]

|  |  |

A cimolodontid multituberculate.

C. sp.[131]

* North Dakota[131]

|  |  |

A cimolodontid multituberculate.

Cimolomys[131]

C. gracilis

* Montana[131]

|  |  |

A cimolomyid multituberculate.

* C. cf. gracilis[131]

* South Dakota[131]

|  |  |

A cimolomyid multituberculate.

Essonodon[131]

E. browni[131]

* Montana[131]

|  |  |

A cimolomyid multituberculate.

Meniscoessus[131]

M. conquistus

* South Dakota[131]

|  |  |

A cimolomyid multituberculate.

M. robustus

* Montana
* North Dakota
* South Dakota[131]

|  |  |

A cimolomyid multituberculate.

M. cf. robustus

* South Dakota[131]

|  |  |

A cimolomyid multituberculate.

M. sp.

* North Dakota[131]

|  |  |

A cimolomyid multituberculate.

?M. sp.[131]

* North Dakota[131]

|  |  |

A cimolomyid multituberculate.

Mesodma[131]

M. formosa

* Montana
* South Dakota[131]

|  |  |

A neoplagiaulacid multituberculate.

M. cf. formosa

* Montana[131]

|  |  |

A neoplagiaulacid multituberculate.

M. hensleighi

* Montana
* South Dakota[131]

|  |  |

A neoplagiaulacid multituberculate.

M. cf. hensleighi

* South Dakota[131]

|  |  |

A neoplagiaulacid multituberculate.

M. thompsoni

* Montana
* North Dakota
* South Dakota[131]

|  |  |

A neoplagiaulacid multituberculate.

M. cf. thompsoni

* Montana[131]

|  |  |

A neoplagiaulacid multituberculate.

M sp.[131]

* Montana[131]

|  |  |

A neoplagiaulacid multituberculate.

?M sp.[131]

* Montana[131]

|  |  |

A neoplagiaulacid multituberculate.

?Neoplagiaulax[131]

?N. burgessi[131]

* Montana[131]

|  |  |

A neoplagiaulacid multituberculate.

Paracimexomys[131]

P. priscus[131]

* Montana[131]

|  |  |

A multituberculate of uncertain phylogenetic placement.

Paressonodon[132]

P. nelsoni[132]

|  |  |  |

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[131]

A. marshi

* Montana
* North Dakota[131]

|  |  |

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[131]

|  |  |

An alphadontid.

A. wilsoni

* Montana[131]

|  |  |

An alphadontid.

A. cf. wilsoni

* Montana[131]

|  |  |

An alphadontid.

A. sp.[131]

* North Dakota
* South Dakota[131]

|  |  |

An alphadontid.

Didelphodon[131]

D. padanicus

* South Dakota[131]

|  |  |

A stagodontid.

D. vorax

* Montana
* North Dakota[131]

|  |  |

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

D. cf. vorax

* South Dakota[131]

|  |  |

A stagodontid.

D. sp.

* North Dakota[131]

|  |  |

A stagodontid.

cf. D. sp.[131]

* North Dakota
* South Dakota[131]

|  |  |

A stagodontid.

Glasbius[131]

G. twitchelli

* Montana[131]

|  |  |

A glasbiid.

G. cf. twitchelli[131]

* Montana[131]

|  |  |

A glasbiid.

Leptalestes[133]

L. cooki

* Montana[131]

|  |  |

A pediomyid.

L. krejcii[133]

* Montana
* South Dakota[131]

|  |  |

A pediomyid.

Nanocuris[132]

N. improvida[132]

|  |  |  |

A deltatheridiid.

Nortedelphys

N. jasoni (= N. intermedius)[132][134]

* Montana
* South Dakota

|  |  |

A herpetotheriid.

Pediomys[131]

P. elegans[131]

* Montana
* South Dakota[131]

|  |  |

A pediomyid.

Protalphadon[131]

P. foxi

* Montana[131]

|  |  |

An alphadontid.

P. lulli[131]

* Montana[131]

|  |  |

An alphadontid.

Protolambda[133][135] |

P. florencae[133][135]

* Montana
* North Dakota
* South Dakota[131]

|  |  |

A pediomyid.

P. hatcheri[133][135] |

* Montana
* South Dakota[131]

|  |  |

A pediomyid.

P. mcgilli[136] |

* Montana[136]

|  |  |

A pediomyid.

Turgidodon[131]

T. rhaister[131]

* Montana[131]

|  |  |

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

Altacreodus

A. magnus

* Montana
* North Dakota

|  |  |

a possible creodont, formerly a species of Cimolestes[137]

Alostera[131]

A. saskatchewanensis[131]

* Montana[131]

|  |  |

A eutherian of uncertain phylogenetic placement.

Ambilestes

A. cerberoides

* Montana

|  |  |

A eutherian of uncertain classification, formally a species of Cimolestes

Batodon[131]

B. tenuis[131]

* Montana[131]

|  |  |

A cimolestid eutherian.

Cimolestes[131]

C. incisus

* Montana[131]

|  |  |

A cimolestid eutherian.

C. stirtoni[131]

* Montana[131]

|  |  |

A cimolestid eutherian.

Gypsonictops[131]

G. hypoconus

* Montana
* South Dakota[131]

|  |  |

A gypsonictopsid eutherian.

G. illuminatus

* Montana
* North Dakota[131]

|  |  |

A gypsonictopsid eutherian.

G. cf. illuminatus

* Montana[131]

|  |  |

A gypsonictopsid eutherian.

G. sp.[131]

* Montana[131]

|  |  |

A gypsonictopsid eutherian.

cf. Paranyctoides[131]

cf. Paranyctoides sp.[131]

* Montana[131]

|  |  |

A nyctitheriid eutherian.

Protungulatum[133]

P. coombsi[133]

* Montana[133]

|  |  |

A stem-placental.

Purgatorius

P. ceratops

* Montana

|  |  |

A genus with four species believed to be either stem-placentals or stem-primates.

Scollardius

S. propalaeoryctes

* Montana

|  |  |

A eutherian of uncertain classification, formally a species of Cimolestes

## Flora

[edit]

The Hell Creek Formation was a low floodplain at the time before the sea retreated, and in the wet ground of the dense woodland, the diversity of angiosperms and conifers were present. A diversity of herbaceous flowering plants, ferns and moss grew in the forest understory. On the exposed point bars of large river systems, there were shrubs and vines. The evidence of the forested environment is supported by petrified wood, rooted gley paleosols,[138] and ubiquitous tree leaves. The presence of the simple and lobed leaves, combined with a high dicot diversity, extinct cycadeoid Nilssoniocladus, Ginkgo, many types of monocots, and several types of conifers is different from any modern plant community. There are numerous types of leaves, seeds, flowers and other structures from Angiosperms, or flowering plants. The Hell Creek Formation of this layer contains over 300 tablets, of which angiosperms are the most diverse and dominant flora of the population, about 90 percent, followed by about 5% of conifers, 4% of ferns, and others. Compared to today Hell Creek's flora which is prairie, then Hell Creek's flora was hardwood forest mixed with deciduous and evergreen forest. In sharp contrast to the Great Plains today, the presence of some thermophilous taxa such as palm trees and gingers meant the climate was warmer and wetter then.

Fossil fruits from the Hell Creek Formation of Spinifructus antiquus of the palm family (Arecaceae).

The plants of the Hell Creek Formation generally represent angiosperm-dominated riparian forests of variable diversity, depending on stratigraphic position and sedimentary environment. There appears to be floral transitions visible on a stratigraphic range from the lower to the upper Hell Creek Formation. For this reason, Kirk Johnson and Leo Hickey divided it into five zones and described them as HCIa, HCIb, HCIIa, HCIIb, and HCIII as a reflection of floral change through time.[139] For example, the HCIa zone is dominated by "Dryophyllum" subfalcatum, Leepierceia preartocarpoides, "Vitis" stantonii, and "Celastrus" taurenensis, and is located 55 to 105 meters below the K-Pg boundary layer. Although the HCIb zone is a very thin layer, about 5 meters of rock, it bears unusually high diversity of herbaceous and shrubby plants, including Urticaceae, Ranunculaceae, Rosaceae, and Cannabaceae.[140][141]

Bisonia niemii is one of the common fossil leaf species in the HCIII zone.

There is evidence of transitional floras in the middle of the Hell Creek Formation as shown by HCII and HCIII zones. The HCII flora represents a transitional period where taxa from the lower Hell Creek are replaced by the HCIII flora. The diversity of the HCIII zone is very high, and its composition is more uniform than that of HCII, many of which were rare or absent from the zones below, and some others that used to be common below became rarer in the HCIII zone. These forms include Elatides longifolia, "Dryophyllum" tennessensis, Liriodendrites bradacii, and many members of the Laurales including Bisonia niemii, "Ficus" planicostata, and Marmarthia trivialis, while "Celastrus" taurenensis, Leepierceia preartocarpoides, and many cupressaceous conifers became rarer. This phenomenon suggests that the global temperature was warming during the last 300,000-500,000 years of the Cretaceous period.[140][141][142][143]

There is no evidence of fern prairie in the Hell Creek Formation.[144] However, there was high angiosperm diversity — common plane trees, "Dryophyllum" subfalcatum, Leepierceia preartocarpoides, and sabal palms — along with extinct cycadeoid Nilssoniocladus, Ginkgo, araucariaceous, Taxodiaceous, and cupressaceous conifers. This represents the mixed deciduous and evergreen broad-leaved forest of the Hell Creek landscape. The nature of these forests is uncertain because Johnson found that the majority of the angiosperm and conifer genera are now extinct. He also believes that, very roughly 80% of the terrestrial plant taxa died out in what is now Great Plains at the K-Pg boundary. On other hand, 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-Pg boundary layer). This increase in fern spore abundance is commonly referred 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).

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 Ficus 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. Among the localities, the Mud Buttes, located in Bowman County, North Dakota, is probably the richest megaflora assemblage known and the most diverse leaf quarry from the Hell Creek Formation.[141] "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; "DMNH" is for the Denver Museum of Nature & Science; "USNM" is for Smithsonian National Museum of Natural History; and so on. The majority of Hell Creek megafloral specimens are collected at the Denver Museum of Nature & Science.

### Overview (from Johnson, 2002)

[edit]

302 plant morphotypes based on leaf only, including:

* 1 bryophyte (mosses and liverworts)
* 11 ferns
* 1 sphenopsid
* 10 conifers
* 1 ginkgo (uncommon)
* 278 angiosperms (roughly 92% of all taxa found)

### Paleoflora

[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.

#### Liverworts

[edit]

Genus  | Species  | Location  | Stratigraphic position  | Abundance  | Notes  | Images

|
|
|
|
|
|

Marchantia

M. pealii

|  |  |  |

Only known liverwort in Hell Creek.

#### Ferns

[edit]

Genus  | Species  | Location  | Stratigraphic position  | Abundance  | Notes  | Images

|
|
|
|
|
|

Equisetum

E. sp.

|  |  |  |

Rare in the Hell Creek Formation.

Polypodiaceae?

indeterminate

|  |  |  |  |

Salvinia

S. sp.

|  |  |  |

Floating aquatic plant.

#### Cycadophytes

[edit]

Genus  | Species  | Location  | Stratigraphic position  | Abundance  | Notes  | Images

|
|
|
|
|
|

Nilssoniocladus |

N. comtula

|  |  |  | Unlike N. yukonensis, its leaves are pinnatisect pinnules. Common.  |

N. yukonensis

|  |  |  |

The only Hell Creek Formation cycadeoid. A simple leaf. Common.

#### Ginkgoales

[edit]

Genus  | Species  | Location  | Stratigraphic position  | Abundance  | Notes  | Images

|
|
|
|
|
|

Ginkgo

G. adiantoides

|  |  |  |

The only ginkgoalean in the Hell Creek Formation; uncommon

#### Conifers

[edit]

Genus  | Species  | Location  | Stratigraphic position  | Abundance  | Notes  | Images

|
|
|
|
|
|

Cupressinocladus

C. interruptus

|  |  |  |

Casts of cupressaceae foliage, very common.[145]

Dammarites

D. sp.

|  |  |  | A conifer seed cone. It's likely to belong to Elatides longifolia.[145] |

Ditaxocladus

D. catenulata

|  |  |  |

A cupressaceous conifer closely related to Cupressinocladus, Common.[145]

Elatides

E. longifolia

|  |  |  |

Araucaria-like conifer. Less common in the lower 2/3 but more common in the upper 1/3 of the Hell Creek Formation.[141]

Glyptostrobus |

G. europaeus

|  |  |  | A very common conifer.[145] |

Metasequoia

M. occidentalis

|  |  |  |

M. occidentalis seed cones are known from the Hell Creek.[145]

Sequoia | S. dakotensis[146] |  |  |  | A sequoioid known from cones.  |

Taxodium

T. olrikii

|  |  |  |

Related to today's bald cypress.[145]

#### Angiosperms

[edit]

Genus  | Species  | Location  | Stratigraphic position  | Abundance  | Notes  | Images

|
|
|
|
|
|

"Artocarpus"

"A." lessigiana

|  |  |  |

Abundant at Brownie Butte, Montana. Affinities with Sassafras in the Lauraceae.[147]

Araliaephyllum |

A. polevoi

|  |  |  | A lobed leaf. Closely relating to Bisonia. Fairly common.[145] |
Averrhoites | cf. A. affinis |  |  |  | An uncommon taxon with compound leaves.  |
Berberidaceae indet.  |  |  |  |  | Common in HClb.[148] |
“Betula” | “B.” perantigua |  |  |  | Incertae sedis. Venation and tooth form consistent with the extant Betula.[149] |
Bisonia |

B. niemi

|  |  |  |

Belongs to Lauraceae, A common taxon. Type specimen was found in South Dakota.[145]

Browniea | B. serrata |  |  |  | In the Nyssaceae, closely relating to extant Camptotheca. Less common.[150] |
Cannabaceae indet.  |  |  |  |  | Belongs in Cannabaceae.[145][151] |

Carpites | C. ulmiformis |  |  |  | Though this fossil fruit is abundant in the Early Paleocene, it's also found in Hell Creek. It may belong to Apiaceae.[152] |

"Celastrus"

"C." taurenensis

|  |  |  |

Incertae sedis. It's common in the lowermost to the middle Hell Creek Formation, but less common in the upper 1/3 Hell Creek Formation.[141]

"Cinnamomum"

"C." lineafolia

|  |  |  |

Included in Ficus affinis by L. Hickey. Some other specimens referred to Cinnamomum sezanensis(?) sp.), a real cinnamon bush. Its affinity is questionable.[145]

Cissites | cf. C. acerifolia |  |  |  | This morphotype was first described from the Cenomanian Dakota Group.[140] |

C. insignis

|  |  |  |

This form is represented in the group of Cenomanian leaves from the Dakota Formation.[140]

C. lobata

|  |  |  | A lobed leaf with half-naked basal lateral veins. Common in the upper 1/3 of the Hell Creek Formation.[145] |

C. puilasokensis

|  |  |  | A palmately lobed leaf with 5 primary veins. Common in the upper 1/3 of the Hell Creek Formation.[145] |

Cobbania

C. corrugata

|  |  |  |

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

C. hickeyi |  |  |  | Another Cobbania species from pond sediments known as "Licking Leaves."[153]
Cornophyllum | C. newberryi |  |  |  | The majority of leaves are entire-margined but some may develop a few teeth. Belongs to Cornaceae.[140] |
"Cyperacites" | "C." sp. |  |  |  | A reed-type plant.  |
Dicotophyllum | D. anomalum |  |  |  | Incertae sedis.[154] |
Dryophyllum |

D. subfalcatum

|  |  |  |

This taxon is very common in the Hell Creek Formation, but is rare in Paleocene sediments.
It is believed to be in Sabiaceae, closely related to the living Meliosma.[140][155][better source needed]

"D." tenneseensis

|  |  |  | This taxon is similar to D. subfalcatum but with high L/W ratio and craspedodromous venation.[140] |
Erlingdorfia |

E. montana

|  |  |  |

Johnson, 1996. In the Platanaceae. A very common taxon.[145]

Fagaceae indet.  |  |  |  |  | Indeterminate Fagaceous leaves.[154] |

"Ficus"

"F." planicostata

|  |  |  | Despite the genus name, it's in Lauraceae.[145] |

Grewiopsis

G. saportana

|  |  |  |

Belongs to Platanaceae.[145]

Harmsia

H. hydrocotyloidea

|  |  |  | Incertae sedis. An uncommon taxon.[145] |

Humulus?

aff. H sp.

|  |  |  | May be related to the extant genus Humulus.[145][151] |

Hydropteris

H. pinnata

|  |  |  |

Floating aquatic fern.[145]

Limnobiophyllum |

L. scutatum

|  |  |  | Floating aquatic monocot, closely related to Lemna.[153] |

Liriodendrites

L. bradacii

|  |  |  |

Johnson, 1996. Belongs to Magnoliaceae, a common taxon.[145]

"Liriodendron"

"L." laramiense

|  |  |  | Unlobed leaf. Related to Liriodendron, an uncommon taxon.[145] |

Liriodendron

L. sp.

|  |  |  |

Four-lobed leaf. Related to Liriodendron, an uncommon taxon.[145]

Leepierceia

L. preartocarpoides

|  |  |  |

Belong to Platanaceae. Johnson, 1996.[145]

Laurophyllum |

L. wardiana

|  |  |  | Large leaves, closely related to "Dryophyllum" subfalcatum.  |
L. lanceolatum |  |  |  | Belongs to Lauraceae.[149] |
Marmarthia |

M. johnsonii

|  |  |  | A new Marmarthia species described in Peppe et al. 2007. Similar to Lindera.[156] |

M. pearsonii

|  |  |  |

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

M. trivialis

|  |  |  |

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

"Myrica"

"M." torreyi

|  |  |  | Incertae sedis. Not actually a bayberry.[145] |

Nelumbo

N. sp.

|  |  |  | One of the most common aquatic plants in Hell Creek.[145] |
Nelumbium |

N. montanum

|  |  |  | An aquatic angiosperm, closely related to lotus. Uncommon.[145] |
Nordenskioldia |

N. borealis

|  |  |  |

A fossil fruit likely to belonging to Zizyphoides flabella.[157]

Paranymphaea

P. hastata

|  |  |  | Despite the name, it's not related to extant genus Nymphaea. Belongs to Polygonaceae.[147] |
Palaeoaster |

P. porosa

|  |  |  |

A papaveraceous fruit.[158]

Penosphyllum

P. cordatum

|  |  |  | Related to Sterculioideae. A common taxon.[147] |

Platanites

P. marginata

|  |  |  |

Johnson, 1996. Belongs to Platanaceae, a common taxon.[145]

P. raynoldsii

|  |  |  | An uncommon taxon.  |
Platanophyllum | P. sp. |  |  |  | Belongs to Platanaceae. Common in the lowermost Hell Creek.[149] |

Porosia

P. verrucosa

|  |  |  | A fossil fruit that may belong to Rutaceae.[159] |

Quereuxia

Q. angulata

|  |  |  |

A water caltrop look-alike.[145]

Rannunculaceae indet.  |  |  |  |  | Common in HCIb.[160] |

Rhamnica

R. cleburnii

|  |  |  |

Possibly belongs to Rhamnaceae.[147][161]

Rosaceae indet.  |  |  |  |  | Very common in HCIb.[161] |

Sabalites

S. sp.

|  |  |  |

Coryphoid palm frond. A common taxon.[145]

Cf. Sarcandra | cf. S. sp. |  |  |  | Venation and tooth form similar to Sarcandra glabra. Belongs to Chloranthaceae.[149] |

Spinifructus

S. antiquus

|  |  |  |

A fruit seed that may belong to the palm family (Arecaceae).[162]

Symplocarpus | S. hoffmaniae |  |  |  | Originally described as aff. Philodendron, now known to be related to Symplocarpus.[163] |

Trochodendroides

T. arctica

|  |  |  | A fossil fruit that may belong to Trochodendroides nebrascensis.  |
T. ellipticum |  |  |  | A katsura look-alike. An uncommon taxon.  |
T. genetrix |  |  |  | A katsura look-alike. A common taxon.  |

T. nebrascensis

|  |  |  | A very common taxon.  |
Urticaceae indet.  |  |  |  |  | Common in HCIb.[164] |

"Vitis"

"V." stantonii

|  |  |  |

Possibly a member of the Platanaceae rather than Vitaceae[141][165]

"Ziziphus"

"Z." fibrillosus

|  |  |  | A common taxon, possibly in Piperaceae.[145] |

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)).

Z. magnifolia |  |  |  | Another Zinigberopsis species, previously assigned to Canna? magnifolia.  |

Zizyphoides

Z. flabella

|  |  |  | An uncommon taxon.[145] |

### Palynology

[edit]

Genus  | Species  | Location  | Stratigraphic position  | Abundance  | Notes  | Images

|
|
|
|
|
|

Abietineaepollenites |

Abietineaepollenites foveoreticulatus[166]

Montana

|  |  |

A conifer palynomorph

Abietineaepollenites microalatus[166]

Montana

|  |  |

A conifer palynomorph

Abietineaepollenites varius[166]

Montana

|  |  |

A conifer palynomorph

Acanthotriletes

Acanthotriletes levidensis[166]

Montana

|  |  |  |

Alnipollenites

Alnipollenites verus[166]

Montana

|  |  |  |

Appendicisporites

Appendicisporites tricornitatus[166]

Montana

|  |  |  |
Aquilapollenites |

Aquilapollenites amplus[166]

Montana

|  |  |  |

Aquilapollenites attenuatus

|  |  |  |  |

Aquilapollenites collaris

|  |  |  |  |

Aquilapollenites conatus[166]

Montana

|  |  |  |

Aquilapollenites delicatus[166]

Montana

|  |  |  |

Aquilapollenites marmarthensis

|  |  |  |  |

Aquilapollenites polaris[166]

Montana

|  |  |  |

Aquilapollenites pulvinus[166]

Montana

|  |  |  |

Aquilapollenites pyriformis[166]

Montana

|  |  |  |

Aquilapollenites quadricretaeus

|  |  |  |  |

Aquilapollenites quadrilobus

|  |  |  |  |

Aquilapollenites reductus[166]

Montana

|  |  |  |

Aquilapollenites reticulatus[166]

Montana

|  |  |  |

Aquilapollenites senonicus

|  |  |  |  |

Aquilapollenites turbidus

|  |  |  |  |

Aquilapollenites striatus

|  |  |  |  |

Azolla

Azolla cretacea[166]

Montana

|  |  |

A mosquito fern palynomorph

Balmeisporites

Balmeisporites sp.

|  |  |  |  |

Calamospora

Calamospora mesozoica[166]

Montana

|  |  |  |

Camarozonosporites

Camarozonosporites heskemensis[166]

Montana

|  |  |  |
Cicatricosisporites |

Cicatricosisporites carlylensis[166]

Montana

|  |  |  |

Cicatricosisporites dorogensis[166]

Montana

|  |  |  |
Cingulatisporites |

Cingulatisporites dakotaensis[166]

Montana

|  |  |  |

Cingulatisporites scabratus[166]

Montana

|  |  |  |

Clavatricolpites

Clavatricolpites prolatus[166]

Montana

|  |  |  |
Concavisporites |

Concavisporites rugulatus[166]

Montana

|  |  |  |

Concavisporites rugulatus[166]

Montana

|  |  |  |

Converrucosisporites

Converrucosisporites sp.[166]

Montana

|  |  |  |

Corylus

Corylus granilabratus[166]

Montana

|  |  |

A hazelnut palynomorph

Cupanieidites

Cupanieidites major[166]

Montana

|  |  |  |
Cyathidites |

Cyathidites foveolatus[166]

Montana

|  |  | A tree fern palynomorph  |

Cyathidites minor[166]

Montana

|  |  | A tree fern palynomorph  |
Cyathidites australis | North Dakota  |  |  | A tree fern palynomorph  |
Cyathidites diaphana  | North Dakota[167] |  |  | A tree fern palynomorph  |

Cycadopites

Cycadopites scabratus[166]

Montana

|  |  |  |

Deltoidospora

Deltoidospora diaphana[166]

Montana

|  |  |  |

Dicotetradites

Dicotetradites granulatus[166]

Montana

|  |  |  |
Ephedripites |

Ephedripites ovatus[166]

Montana

|  |  |  |

Ephedripites undulatus[166]

Montana

|  |  |  |

Erdtmanipollis

Erdtmanipollis cretaceus[166]

Montana
South Dakota

|  |  |  |
Gleicheniidites |

Gleicheniidites excelsus[166]

Montana

|  |  |  |

Gleicheniidites senonicus[166]

Montana

|  |  |  |

Gnetaceaepollenites

Gnetaceaepollenites eocenipites[166]

Montana

|  |  |  |

Haloragacidites

Haloragacidites quadratus[166]

Montana

|  |  |  |

Hamulatisporis

Hamulatisporis hamulatis[166]

Montana

|  |  |  |
Hymenophyllumsporites |

Hymenophyllumsporites parvus[166]

Montana

|  |  |

A fern spore palynomorph

Hymenophyllumsporites pseudomaximus[166]

Montana

|  |  |

A fern spore palynomorph

Ilexpollenites

Ilexpollenites compactus

|  |  |  |  |

Inaperturopollenites

Inaperturopollenites rugulatus[166]

Montana

|  |  |  |

Interpollis

Interpollis cf. I. supplingensis

|  |  |  |  |
Kurtzipites |

Kurtzipites trispissatus[166]

Montana

|  |  |  |

Kurtzipites trispissatus[166]

Montana

|  |  |  |
Laevigatosporites |

Laevigatosporites anomalus[166]

Montana

|  |  |  |

Laevigatosporites discordatus[166]

Montana

|  |  |  |

Laevigatosporites gracilis[166]

Montana

|  |  |  |

Laevigatosporites ovatus[166]

Montana

|  |  |  |
Liliacidites |

Liliacidites variegatus[166]

Montana

|  |  |  |

Liliacidites sp.[166]

Montana

|  |  |  |

Lycopodiumsporites

Lycopodiumsporites austroclavatidites[166]

Montana

|  |  |  |
Momipites |

Momipites circularis[166]

Montana

|  |  |  |

Momipites parvus[166]

Montana

|  |  |  |
Monosulcites |

Monosulcites carpentieri[166]

Montana

|  |  |  |

Monosulcites crescentus[166]

Montana

|  |  |  |

Monosulcites latus[166]

Montana

|  |  |  |

Monosulcites tectatus[166]

Montana

|  |  |  |

Monosulcites sp.[166]

Montana

|  |  |  |
Myrtipites |

Myrtipites granulatus[166]

Montana

|  |  |  |

Myrtipites scabratus[166]

Montana

|  |  |  |
Nyssapollenites |

Nyssapollenites analepticus[166]

Montana

|  |  |  |

Nyssapollenites pseudocruciatus[166]

Montana

|  |  |  |

Osmundacidites

Osmundacidites wellmanii[166]

Montana

|  |  |  |

Pachysandra

Pachysandra cretaceae[166]

Montana
South Dakota

|  |  |  |

Palmidites

Palmidites maximus[166]

Montana

|  |  |  |

Peromonolites

Peromonolites granulatus[166]

Montana

|  |  |  |
Phyllocladidites |

Phyllocladidites mawsonii[166]

Montana

|  |  |  |

Phyllocladidites ruei[166]

Montana

|  |  |  |

Podocarpidites

Podocarpidites otagoensis[166]

Montana

|  |  |  |

Pinuspollenites

Pinuspollenites labdacus

North Dakota

|  |  | A pine palynomorph showing evidence of the genus Pinus in Hell Creek.[167]
Pinuspollenites sp | North Dakota  |  |  | A pine palynomorph showing evidence of the genus Pinus in Hell Creek.[167]
Piceapollis | Piceapollis sp | North Dakota[167] |  |  | A spruce palynomorph

Polyadopollenites

Polyadopollenites psilatus[166]

Montana

|  |  |  |

Polycolpites

Polycolpites granulatus[166]

Montana

|  |  |  |

Polypodiidites

Polypodiidites inangahuensis[166]

Montana

|  |  |  |
Proteacidites |

Proteacidites retusus[166]

Montana

|  |  |  |

Proteacidites retusus[166]

Montana

|  |  |  |

Proteacidites thalmannii[166]

Montana

|  |  |  |

Psilatricolporites

Psilatricolporites prolatus[166]

Montana

|  |  |  |

Pterocaryapollenites

Pterocaryapollenites stellatus[166]

Montana

|  |  |  |

Reticuloidosporites

Reticuloidosporites dentatus[166]

Montana

|  |  |  |
Schizosporis |

Schizosporis complexus[166]

Montana

|  |  |  |

Schizosporis parvus[166]

Montana

|  |  |  |

Spheripollenites

Spheripollenites subgranulatus[166]

Montana

|  |  |  |

Spinamonoporites

Spinamonoporites typicus[166]

Montana

|  |  |  |
Stereisporites |

Stereisporites antiquasporites[166]

Montana

|  |  |  |

Stereisporites psilatus[166]

Montana

|  |  |  |

Striainaperturites

Striainaperturites ovatus[166]

Montana

|  |  |  |
Styx |

Styx major[166]

Montana

|  |  |  |

Styx minor[166]

Montana

|  |  |  |

Taxodiaceaepollenites

Taxodiaceaepollenites hiatus[166]

Montana

|  |  |  |

Triatriopollenites

Triatriopollenites granilabratus[166]

Montana

|  |  |  |
Tricolpites |

Tricolpites bacustriatus[166]

Montana

|  |  |  |

Tricolpites delicatulus[166]

Montana

|  |  |  |

Tricolpites foveolatus[166]

Montana

|  |  |  |

Tricolpites interangulus

|  |  |  |  |

Tricolpites parvistriatus[166]

Montana

|  |  |  |

Tricolpites psilascabratus[166]

Montana

|  |  |  |

Tricolpites reticulatus[166]

Montana

|  |  |  |

Tricolpites striatus[166]

Montana

|  |  |  |
Tricolpopollenites |

Tricolpopollenites clavireticulatus[166]

Montana

|  |  |  |

Tricolpopollenites megaexactus[166]

Montana

|  |  |  |

Tricolpopollenites microreticulatus[166]

Montana

|  |  |  |

Tricolpopollenites microscabratus[166]

Montana

|  |  |  |

Tricolpopollenites sp1, sp2[166]

Montana

|  |  |  |
Tricolporopollenites |

Tricolporopollenites elongatus[166]

Montana

|  |  |  |

Tricolporopollenites foveotectatus[166]

Montana

|  |  |  |

Tricolporopollenites granustriatus[166]

Montana

|  |  |  |

Tricolporopollenites megaexactus[166]

Montana

|  |  |  |

Tricolporopollenites prolatus[166]

Montana

|  |  |  |

Tricolporopollenites striatus[166]

Montana

|  |  |  |

Triplanosporites

Triplanosporites sinuosus[166]

Montana

|  |  |  |

Triporopollenites

Triporopollenites rugatus[166]

Montana

|  |  |  |
Ulmipollenites |

Ulmipollenites undulosus[166]

Montana

|  |  |  |

Ulmipollenites verrucatus[166]

Montana

|  |  |  |

Ulmoideipites

Ulmoideipites tricostatus[166]

Montana

|  |  |  |

Wodehouseia

Wodehouseia spinata[166]

Montana

|  |  |  |

Zlivisporis

Zlivisporis blanensis[166]

Montana

|  |  |  |

## See also

[edit]

* List of fossil sites (with link directory)
* Lists of dinosaur-bearing stratigraphic units
* Paleobiota of the Morrison Formation
* Lance fauna
* Cretaceous-Paleogene formations
* Tremp Formation, Spain
* Tremp Formation, Spain
* Lefipán Formation, Argentina
* Lopez de Bertodano Formation, Antarctica

## References

[edit]

1. ^ a b c DePalma, Robert; Cichocki, Frederich; Dierick, Manuel; Feeney, Robert (2010). "Preliminary Notes on the First Recorded Amber Insects from the Hell Creek Formation" (PDF). The Journal of Paleontological Sciences. 10: 1–7. Retrieved 16 November 2020.
2. ^ a b Nel, André; DePalma, Robert A.; Engel, Michael S. (2010). "A possible hemiphlebiid damselfly in Late Cretaceous amber from South Dakota (Odonata: Zygoptera)". Transactions of the Kansas Academy of Science. 113 (3/4): 231–234\. doi:10.1660/062.113.0312. JSTOR 41309615. S2CID 84827761.
3. ^ Messer, A'ndrea Eluse. "Leaf-mining insects destroyed with the dinosaurs, others quickly appeared". Penn State News. Pennsylvania State University. Retrieved 20 August 2014.
4. ^ "North Dakota site shows wreckage from same object that killed the dinosaurs". UW News. University of Washington. Retrieved 29 March 2019.
5. ^ Peterson, Douglas. "The Day the Dinosaurs Died". The New Yorker.
6. ^ Nel, André (2021). "Maastrichtian representatives of the dragonfly family Aeschnidiidae question the entomofaunal turnover of the early Late Cretaceous". Palaeoentomology. 4 (3). Bibcode:2021Plegy...4..3.5N. doi:10.11646/palaeoentomology.4.3.5. Retrieved 17 Feb 2024.
7. ^ a b c d e Graf, Dan; Cummings, Kevin. "The Mussel Project". UWSP Mussel Project. The University of Wisconsin-Stevens Point. Retrieved 7 June 2021.
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 as at au av aw Pearson et al. (2002) p. 154
9. ^ 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 Pearson et al. (2002) pp. 145–167
10. ^ a b c d e f g h i j k l m n o p q Pearson et al. (2002) p. 155
11. ^ a b c d e f g h i j k l m n o p q r s Pearson et al. (2002) pp. 156
12. ^ Listed as "cf. Barbourula sp." in "Class Amphibia," Estes and Berberian, (1970). Page 4.
13. ^ 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.
14. ^ 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.
15. ^ Listed as "Eopelobates? sp." in "Class Amphibia," Estes and Berberian, (1970). Page 4.
16. ^ 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\. Bibcode:2013JVPal..33..588D. doi:10.1080/02724634.2013.734887. S2CID 128532897.
17. ^ 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.
18. ^ a b c d e f g Hilton, Eric J.; Grande, Lance (2022-10-03). "Late Cretaceous sturgeons (Acipenseridae) from North America, with two new species from the Tanis site in the Hell Creek Formation of North Dakota". Journal of Paleontology. 97 (1): 189–217\. doi:10.1017/jpa.2022.81. S2CID 252702937.
19. ^ 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.
20. ^ a b c d Sato, Hiroki; Murray, Alison M.; Vernygora, Oksana; Currie, Philip J. (4 July 2018). "A rare, articulated sturgeon (Chondrostei: Acipenseriformes) from the Upper Cretaceous of Dinosaur Provincial Park, Alberta, Canada". Journal of Vertebrate Paleontology. 38 (4): (1)-(15). doi:10.1080/02724634.2018.1488137. S2CID 92574712.
21. ^ a b c d "Class Osteichthyes," in Estes and Berberian, (1970). Page 4.
22. ^ a b c "Class Osteichthyes," in Estes and Berberian, (1970). Page 4. All taxa listed occur in Montana, see page 1.
23. ^ Grande, Lance; Bemis, William E. (10 April 1998). "A Comprehensive Phylogenetic Study of Amiid Fishes (Amiidae) Based on Comparative Skeletal Anatomy. an Empirical Search for Interconnected Patterns of Natural History". Journal of Vertebrate Paleontology. 18 (sup1): 1–696\. Bibcode:1998JVPal..18S...1G. doi:10.1080/02724634.1998.10011114.
24. ^ Grande, Lance (2010). "An Empirical Synthetic Pattern Study of Gars (lepisosteiformes) and Closely Related Species, Based Mostly on Skeletal Anatomy. the Resurrection of Holostei". Copeia. 2010 (2A): iii–871. JSTOR 20787269.
25. ^ a b Listed as "cf. Paralbula casei" in "Class Osteichthyes," Estes and Berberian, (1970). Page 4.
26. ^ a b c d e f Hilton, Eric J.; During, Melanie A.D.; Grande, Lance; Ahlberg, Per E. (May 2023). "New paddlefishes (Acipenseriformes, Polyodontidae) from the Late Cretaceous Tanis Site of the Hell Creek Formation in North Dakota, USA". Journal of Paleontology. 97 (3): 675–692\. Bibcode:2023JPal...97..675H. doi:10.1017/jpa.2023.19. S2CID 258095684.
27. ^ a b c Grande, Lance; Bemis, William E. (1991). "Osteology and Phylogenetic Relationships of Fossil and Recent Paddlefishes (Polyodontidae) with Comments on the Interrelationships of Acipenseriformes". Memoir. 1. Society of Vertebrate Paleontology: ii–121. doi:10.2307/3889328. JSTOR 3889328.
28. ^ a b c d e f g h i j k l m n o p q r s Todd D. Cook; Michael G. Newbrey; Donald B. Brinkman; James I. Kirkland (2014). "Euselachians from the freshwater deposits of the Hell Creek Formation of Montana". Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas. Geological Society of America Special Papers. Vol. 503\. pp. 229–246\. doi:10.1130/2014.2503(08). ISBN 978-0-8137-2503-1.
29. ^ a b Terry A. Gates; Eric Gorscak; Peter J. Makovicky (2019). "New sharks and other chondrichthyans from the latest Maastrichtian (Late Cretaceous) of North America". Journal of Paleontology. 93 (3): 512–530\. Bibcode:2019JPal...93..512G. doi:10.1017/jpa.2018.92.
30. ^ a b "Class Chondrichthyes," in Estes and Berberian, (1970). Page 3.
31. ^ "Class Chondrichthyes," in Estes and Berberian, (1970). Page 3. All taxa listed occur in Montana, see page 1.
32. ^ "Stratigraphy and paleontology of the Cretaceous Hell Creek Formation, Stumpf site, Morton County, North Dakota". Proceedings of the North Dakota Academy of Sciences. 48. 1994.
33. ^ White, Paul; Fastovsky, David; Sheehan, Peter (1998). "Taphonomy and suggested structure of the dinosaurian assemblage of the Hell Creek Formation (Maastrichtian), eastern Montana and western North Dakota". PALAIOS. 13 (1): 41. Bibcode:1998Palai..13...41W. doi:10.2307/3515280. JSTOR 3515280.
34. ^ Manning, P. L.; Ott, C.; Falkingham, P. L. (2008). "The first tyrannosaurid track from the Hell Creek Formation (Late Cretaceous), Montana, U.S.A". PALAIOS. 23 (10): 645–647\. Bibcode:2008Palai..23..645M. doi:10.2110/palo.2008.p08-030r. S2CID 129985735.
35. ^ a b Lockley, M.; Triebold, M.; Janke, P. R. (2014). "Dinosaur Tracks from the Hell Creek Formation (Upper Cretaceous, Maastrichtian), South Dakota". Fossil Footprints of Western North America: New Mexico Museum of Natural History and Science, Bulletin. 62: 459–468.
36. ^ a b c d Carpenter, Kenneth; Breithaupt, Brent (2 September 1986). "Latest Cretaceous occurrence of nodosaurid ankylosaurs (Dinosauria, Ornithischia) in Western North America and the gradual extinction of the dinosaurs". Journal of Vertebrate Paleontology. 6 (3): 251–257\. Bibcode:1986JVPal...6..251C. doi:10.1080/02724634.1986.10011619.
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39. ^ a b Bakker, R.T. (1988). Review of the Late Cretaceous nodosauroid Dinosauria: Denversaurus schlessmani, a new armor-plated dinosaur from the Latest Cretaceous of South Dakota, the last survivor of the nodosaurians, with comments on Stegosaur-Nodosaur relationships. Hunteria 1(3):1–23.(1988).
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43. ^ Fowler, D.W. (2017). "'Revised geochronology, correlation, and dinosaur stratigraphic ranges of the Santonian-Maastrichtian (Late Cretaceous) formations of the Western Interior of North America". PLOS ONE. 12 (11): 1–20\. Bibcode:2017PLoSO..1288426F. doi:10.1371/journal.pone.0188426. PMC 5699823. PMID 29166406.
44. ^ Evans, David; Brown, Caleb M.; You, Hailu; Campione, Nicolás E. (2021). "Description and revised diagnosis of Asia's first recorded pachycephalosaurid, Sinocephale bexelli gen. nov., from the Upper Cretaceous of Inner Mongolia, China". Canadian Journal of Earth Sciences. 58 (10): 981–992\. Bibcode:2021CaJES..58..981E. doi:10.1139/cjes-2020-0190. S2CID 244227050.
45. ^ Wroblewski, A. F.-J. (2025). "Southernmost record of the pachycephalosaurine Stygimoloch spinifer and palaeobiogeography of latest Cretaceous North American dinosaurs". Lethaia. 57 (4): 1–10\. doi:10.18261/let.57.4.7.
46. ^ a b c d e f g h i j "Dinosaur distribution (Late Cretaceous; North America; South Dakota)." Weishampel, et al. (2004). Page 586.
47. ^ a b c d e Horner, John R.; Goodwin, Mark B.; Evans, David C. (28 October 2022). "A new pachycephalosaurid from the Hell Creek Formation, Garfield County, Montana, U.S.A.". Journal of Vertebrate Paleontology. 42 (4). Bibcode:2022JVPal..42E0369H. doi:10.1080/02724634.2023.2190369. S2CID 258154892.
48. ^ Williamson, Thomas E.; Carr, Thomas D. (2003). "A new genus of derived pachycephalosaurian from western North America". Journal of Vertebrate Paleontology. 22 (4): 779–801\. doi:10.1671/0272-4634(2002)022[0779:ANGODP]2.0.CO;2. S2CID 86112901.
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77. ^ a b Listed as "?Thescelosaurus garbanii" in "Dinosaur distribution (Late Cretaceous; North America; Montana)." Weishampel, et al. (2004). Page 584.
78. ^ a b Boyd, Clint A.; Brown, Caleb Marshal; Scheetz, Rodney D.; Clarke, Julia A. (12 September 2009). "Taxonomic Revision of the Basal Neornithischian Taxa Thescelosaurus and Bugenasaura". Journal of Vertebrate Paleontology. 29 (3): 758–770\. Bibcode:2009JVPal..29..758B. doi:10.1671/039.029.0328. JSTOR 20627088. S2CID 84273584.
79. ^ Noted as being present, although misspelled as "Thescelosaurus garbani, in " "Dinosaur distribution (Late Cretaceous; North America; South Dakota)." Weishampel, et al. (2004). Page 586.
80. ^ Boyd, Brown, et al. (2009)
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84. ^ Molnar, R.E. (January 1980). "An Albertosaur from the Hell Creek Formation of Montana". Journal of Paleontology. 54 (1): 102–108\. JSTOR 1304167.
85. ^ Molnar, R. E. (January 1978). "A New Theropod Dinosaur from the Upper Cretaceous of Central Montana". Journal of Paleontology. 52 (1): 73–82\. JSTOR 1303791.
86. ^ a b Denver W. Fowler; John P. Wilson; Elizabeth A. Freedman Fowler; Christopher R. Noto; Daniel Anduza; John R. Horner (2020). "Trierarchuncus prairiensis gen. et sp. nov., the last alvarezsaurid: Hell Creek Formation (uppermost Maastrichtian), Montana". Cretaceous Research. 116: Article 104560. Bibcode:2020CrRes.11604560F. doi:10.1016/j.cretres.2020.104560. S2CID 225630913.
87. ^ Hutchinson and Chiappe, 1998. The first known alvarezsaurid (Theropoda: Aves) from North America. Journal of Vertebrate Paleontology. 18(3), 447–450.
88. ^ Horner, John R.; Goodwin, Mark B.; Myhrvold, Nathan (9 February 2011). "Dinosaur Census Reveals Abundant Tyrannosaurus and Rare Ontogenetic Stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA". PLOS ONE. 6 (2): e16574. Bibcode:2011PLoSO...616574H. doi:10.1371/journal.pone.0016574. PMC 3036655. PMID 21347420.
89. ^ 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
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* 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, 100 (11): 1041–1049, Bibcode:2013NW....100.1041E, doi:10.1007/s00114-013-1107-5, PMID 24248432 Bibcode:/abstract 2013NW....100.1041E
* 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, Bibcode:2011E&PSL.305..328H, doi:10.1016/j.epsl.2011.03.008 Bibcode:2011E&PSL.305..328H
* LeCain, Rebecca (2010), "Magnetostratigraphy of the Hell Creek and lower Fort Union formations in northeast Montana", Master's Theses and Capstones, p. 1, retrieved 2020-03-30
* 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

Paleontology

* DePalma, Robert (2010), "Preliminary Notes on the First Recorded Amber Insects from the Hell Creek Formation", The Journal of Paleontological Sciences, retrieved 2019-02-21
* 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, Bibcode:2009JVPal..29..758B, doi:10.1671/039.029.0328
* 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, Bibcode:2008Palgy..51..983L, doi:10.1111/j.1475-4983.2008.00791.x
* Manning, P.L.; Ott, C.; Falkingham, P.L. (2008), "The first tyrannosaurid track from the Hell Creek Formation (Late Cretaceous), Montana, U.S.A", PALAIOS, 23 (10): 645–647, Bibcode:2008Palai..23..645M, doi:10.2110/palo.2008.p08-030r Bibcode:2008Palai..23..645M
* Bakker, R.T.; Sullivan, R.M.; Porter, V.; Larson, P.; 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" (PDF), New Mexico Museum of Natural History and Science Bulletin, 35: 331–354, archived from the original (PDF) on 2011-07-17
* Henderson, M.D.; Peterson, J.E. (2006), "An azhdarchid pterosaur cervical vertebra from the Hell Creek Formation (Maastrichtian) of southeastern Montana" (PDF), Journal of Vertebrate Paleontology, 26 (1): 192–195, doi:10.1671/0272-4634(2006)26[192:AAPCVF]2.0.CO;2, JSTOR 4524549, S2CID 130751879
* Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (2004), The Dinosauria, 2nd edition, Berkeley: University of California Press, pp. 1–880, ISBN 0-520-24209-2, retrieved 2019-02-21`{{citation}}`: CS1 maint: publisher location (link)
* Pearson, D.A.; Schaefer, T.; Johnson, K.R.; Nichols, D.J.; Hunter, J.P. (2002), "The Hell Creek Formation and the Cretaceous-Tertiary boundary in the northern Great Plains: An integrated continental record of the end of the Cretaceous", Vertebrate Biostratigraphy of the Hell Creek Formation in Southwestern North Dakota and Northwestern South Dakota, Geological Society of America, Special Paper 361: 145–167, ISBN 9780813723617, retrieved 2019-03-22
* Varricchio, D.J (2001), Late Cretaceous oviraptorosaur (Theropoda) dinosaurs from Montana, D. H. Tanke and K. Carpenter (eds.), Mesozoic Vertebrate Life. Indiana University Press, Indianapolis, Indiana, pp. 42–57
* Currie, P.J.; Padian, K. (1997), The Encyclopedia of Dinosaurs, Academic Press, pp. 1–901, ISBN 978-0-122-26810-6, retrieved 2020-03-30
* Eberth, D.A. (1997). Edmonton Group. San Diego: Academic Press. pp. 199–204. ISBN 978-0-122-26810-6.
* Lofgren, D.F. (1997). Hell Creek Formation. San Diego: Academic Press. pp. 302–303. ISBN 978-0-122-26810-6.
* Breithaupt, B.H (1997). Lance Formation. San Diego: Academic Press. pp. 394–395. ISBN 978-0-122-26810-6.
* Christophel, D.C. (1976), "Fossil floras from the Smoky Tower locality, Alberta, Canada", Palaeontographica, Abt. B, 157
* Chandrasekharam, A. (1974), "Megafossil flora from the Genesee locality, Alberta, Canada", Palaeontographica, Abt. A, 174
* Estes, R.; Berberian, P. (1970), "Paleoecology of a late Cretaceous vertebrate community from Montana", Breviora, 343: 1

## External links

[edit]

* Cretaceous Hell Creek Faunal Facies provides a faunal list
* Phillip Bigelow, "Hell Creek life: Fossil Flora & Fauna, a Paleoecosystem"
* Paleobiology Database: MPM locality 3850 (Hell Creek Formation): Maastrichtian, Montana