Paleobiota of the Hell Creek Formation

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

## Contents

* 1 Invertebrates
* 2 Amphibians
* 3 Fish
* 3.1 Bony fish
* 3.2 Cartilaginous fish
* 4 Dinosaurs
* 4.1 Ornithischians
* 4.1.1 Ankylosaurs
* 4.1.2 Pachycephalosaurs
* 4.1.3 Ceratopsians
* 4.1.4 Ornithopods and relatives
* 4.2 Theropods
* 4.2.1 Alvarezsaurs
* 4.2.2 Tyrannosaurids
* 4.2.3 Ornithomimosaurs
* 4.2.4 Oviraptorosaurs
* 4.2.5 Eumaniraptorans
* 5 Pterosaurs
* 6 Crocodylomorphs
* 7 Plesiosaurs
* 8 Turtles
* 9 Squamata
* 10 Choristoderans
* 11 Mammals
* 11.1 Multituberculates
* 11.2 Metatherians
* 11.3 Eutherians
* 12 Flora
* 13 See also
* 14 References
* 14.1 Bibliography
* 15 External links

## Invertebrates

Insects like Diptera, Zygopteran, and possibly hemiphlebiid damselflies 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]

Invertebrates

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

P. postbiplicatus

|  |  |  |

Freshwater Pelecypods

P. gibbosoides

|  |  |  |

Freshwater Pelecypods

P. whitfieldi

|  |  |  |

Freshwater Pelecypods

Rhabdotophorus | R. aldrichi |  |  |  | Freshwater mussel of family Unionidae.[6] |
Pleurobema | P. cryptorhynchus |  |  |  | Freshwater mussel of family Unionidae.[6] |
Plethobasus | P. aesopiformis |  |  |  | Freshwater mussel of family Unionidae.[6] |
P. biesopoides |  |  |  |  |
Quadrula | Q. cylindricoides |  |  |  | Freshwater mussel of family Unionidae.[6] |
Proparreysia | P. verrucosiformis |  |  |  | Freshwater mussel of family Unionidae.[6] |
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.  |
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.  |
Cephaloleichnites | C. strongi |  |  |  | hispine beetle. ("leaf beetle")  |

## Amphibians

Amphibians reported from the Hell Creek Formation

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

Anura (frog)[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 frog.[7]

Barbourula[11]

Indeterminate[12]

* Montana[13]

|  |  |  |

Caudata (salamander)[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]

* Montana[13]

|  |  |  |

Habrosaurus[7][12]

H. dilatus[7][12]

* Montana[13]
* North Dakota[8]
* South Dakota[8]

Middle to upper Hell Creek Formation[9]

6 specimens[10]

Habrosaurus is a sirenid amphibian.[7]

Lisserpeton[12]

L. bairdi[12]

* Montana[13]

|  |  |  |

Opisthotriton[7][12]

O. kayi[7][12]

* Montana[13]
* North Dakota[8]
* South Dakota[8]

Lower to upper Hell Creek Formation[9]

22 specimens[10]

Opisthotriton is classified as a Batrachosauroididae.[7]

Paranecturus[15]

P. garbanii[15]

* Montana[15]

|  |  |

A member of Proteidae.[15]

Proamphiuma[12]

P. cretacica[12]

* Montana[13]

|  |  |  |

Prodesmodon[12]

P. copei[12]

* Montana[13]

|  |  |  |

Scapherpeton[7][12]

S. tectum[7][12]

* Montana[13]
* North Dakota[8]
* South Dakota[8]

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]

* Montana[13]

|  |  |

A small frog

## Fish

### Bony fish

Bony fishes

Genus | Species | Location | Stratigraphic position | Material | Notes | Images
Acipenser[7][16] | A. eruciferus[16] |

* Montana[17]

|  |  | 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]

* Montana[17]

|  |  |

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

Belonostomus[7][16] | B. longirostris[7][16] |

* Montana[17]
* North Dakota[8]
* South Dakota[8]

| 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] |

* Montana[19]

|  |  |  |
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] |

* Montana[17]
* North Dakota[8]
* South Dakota[8]

| 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] |
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] |
Phyllodus | P. paulkatoi |  |  |  | Fish with columnar teeth  |
Palaeolabrus[16] | P. montanensis[16] |

* Montana[17]

|  |  |  |
Paleopsephurus[16] | P. wilsoni[16] |

* Montana[17]

|  |  | A paddlefish |
Paralbula[20] | P. casei[20] |

* Montana[19]

|  |  |  |
Platacodon[18] | P. nanus[18] |

* Montana[19]

|  |  | Small teleost fish  |
Protamia[16] | Indeterminate[16] |

* Montana[17]

|  |  |  |
Pachyrhizodontoidei  | Indeterminate  |  |  |  | Fish  |
Protoscaphirhynchus[16] | P. squamosus[16] |

* Montana[17]

|  |  | A sturgeon  |

### Cartilaginous fish

Chondrichthyes reported from the Hell Creek Formation

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

Chiloscyllium[21]

C. sp.[21]

* Montana[21]

|  |  |

A member of Hemiscylliidae.[21]

Galagadon[22]

G. nordquistae

* South Dakota

|  |

Isolated teeth

A carpet shark

Lonchidion[23]

L. selachos[23]

* Montana[24]
* North Dakota[8]
* South Dakota[8]

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]

* Montana[21]
* North Dakota[8]
* South Dakota[8]

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]

Protoginglymostoma[21]

P. estesi[21]

* Montana[21]

|  |  |

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

Restesia[21]

R. americana[21]

* Montana[21]
* North Dakota[8]
* South Dakota[8]

Middle Hell Creek Formation[9]

5 specimens previously assigned to Squatirhina[10]

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

Carcharhinidae indet.[22]

Indeterminate

* South Dakota

|  |

An isolated tooth.

|  |

## Dinosaurs

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). [citation needed]

* Ceratopsidae 61%
* Hadrosauridae 23%
* Ornithomimidae 5%
* Tyrannosauridae 4%
* Hypsilophodontidae 3%
* Dromaeosauridae 2%
* 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. 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.[25] 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.[26]

### Ornithischians

#### Ankylosaurs

Indeterminate nodosaur remains have been unearthed in the Hell Creek Formation and other nearby areas.[27][28]

Ankylosauria reported from the Hell Creek Formation

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

Ankylosaurus[29]

A. magniventris[29]

* Montana[29]

| 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[29]

D. schlessmani[29]

* Montana[29]
* South Dakota[30]

|  | Skull roof, pelvis and osteoderms.  |

A nodosaurid ankylosaur whose remains have been found in the Lance and Laramie Formation.[27]

#### Pachycephalosaurs

An undescribed and unnamed pachycephalosaur is present in North Dakota.[31] 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.[32]

Pachycephalosaurs reported from the Hell Creek Formation

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

Dracorex[33]

D. hogwartsia[33]

* South Dakota[33]

* Middle[33]

|  |

A pachycephalosaur, possibly synonymous with Pachycephalosaurus.

Pachycephalosaurus[29]

P. wyomingensis[29]

* Montana[29]
* South Dakota[30]

|  |  |

A pachycephalosaur. Also found in the Lance Formation.

Platytholus[34] | P. clemensi[34] |

* Montana[34]

* Lower[34]

| A partial skull[34] | A medium-sized pachycephalosaurine closely related to Acrotholus and Prenocephale |

Sphaerotholus[29]

S. buchholtzae[29]

* Montana[29]

* Upper[35]

"Skull material."[36]

A pachycephalosaur whose remains have been found in the Frenchman Formation, Kirtland Formation, and the Horseshoe Canyon Formation.

Stygimoloch[29]

S. spinifer[29]

* Montana[29]
* South Dakota
* North Dakota

|  |  |

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

#### Ceratopsians

Indeterminate ceratopsid teeth and some identifiable bones from Triceratops can be extremely common.[37][38][39][40][41] 8.31% of all vertebrate remains from the Hell Creek Formation are unassigned ceratopsids.[10] 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.[42][43][44]

Ceratopsians reported from the Hell Creek Formation

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

Leptoceratops[29]

L. gracilis[29]

|  |

* Montana[29]

|  |  |

A small primitive-looking ceratopsian. Fossils have also been found in the Lance Formation in Wyoming.[45]

Tatankaceratops[46]

T. sacrisonorum[46]

|  |

* South Dakota[46]

|  |  |

A controversial ceratopsian possibly synonymous with Triceratops[47]

Torosaurus[7][29]

T. latus[7][29]

|  |

* Montana[29]
* North Dakota[8][31]
* South Dakota[8][30]

Upper Hell Creek Formation[9]

|  |

A ceratopsian that was once proposed to be synonymous with Triceratops,[48] but is now regarded as a valid and distinct ceratopsian.[49] A rare ceratopsid.[9] Fossils have been in the Lance Formation, Javelina Formation, North Horn Formation, Laramie Formation, El Picacho Formation, Frenchman Formation and Scollard Formation.

Triceratops[7][29]

T. horridus[7][29]

* T. serratus[29]
* Ugrosaurus olsoni[50]

* Montana[29]
* North Dakota[8][31]
* Wyoming
* South Dakota[8][30]

Lowermost to the middle Hell Creek Formation[51]

Four specimens are assigned to Triceratops horridus from the Hell Creek Formation.[10] 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.[7] Also found in the Evanston, Frenchman, Lance, Laramie, and Scollard Formations.

T. prorsus[29]

|  |

* Montana[29]
* South Dakota

| Upper 1/3 of the Hell Creek Formation[51] |

Very common. 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

Indeterminate hadrosaurid remains are very common in the Hell Creek Formation.[7]

Ornithopods and Thescelosaurs reported from the Hell Creek Formation

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

Edmontosaurus

E. annectens

* Anatosaurus annectens[52]
* Anatotitan copei[52]

* Montana[29]
* South Dakota[30]
* North Dakota(Mummy Fossil)[53][54]

|  |

Very common.

A hadrosaur. Also found in the Denver, Frenchman, Lance, Laramie, and Scollard Formations.[55][56] Hatchlings have also been unearthed.[56]

Thescelosaurus[30]

T. garbanii[57][58]

* Bugenasaura garbanii[58]

* Montana[57]
* South Dakota[59]

|  |  |  |

T. neglectus[7][30]

|  |

* North Dakota[8]
* South Dakota[8][30]

Lower to upper Hell Creek Formation[9]

50 specimens[10]

A small thescelosaurine. Also found in the Frenchman, Lance, Laramie, and Scollard Formations.[60] Two species are known from Hell Creek; T. neglectus and T. garbanii.[61]

### Theropods

Theropod tracks have been found in South Dakota.[30] A trackway from South Dakota, named Wakinyantanka, was made by a mid-sized theropod with three slender toes, possibly a small tyrannosaurid.[26] 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.[62] 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.[63][64] Theropod remains are very common in Hell Creek, some of which belong to indeterminate species on maniraptorans.[65]

#### Alvarezsaurs

Alvarezsaurs reported from the Hell Creek Formation

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

Trierarchuncus[29]

T. prairiensis[29]

|  |

* Montana[29]

upper Hell Creek Formation.

|  |

An alvarezsaur known from a partial post-cranial skeleton.[66]

#### Tyrannosaurids

Tyrannosaurids reported from the Hell Creek Formation

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

Tyrannosaurus[7][29]

T. rex[7][29]

* Albertosaurus megagracilis[29]
* Aublysodon molnari[29]
* Dinotyrannus megagracilis[29]
* Nanotyrannus lancensis?

* Montana[29]
* North Dakota[8][31]
* South Dakota[8][30]

Lower to upper Hell Creek Formation.

|  |

A tyrannosaur, known from several specimens including a juvenile nicknamed "Jane".[67] 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.

Nanotyrannus?[7][29]

N.lancensis[7][29]

* Stygivenator?
* Deinodon lancensis
* Albertosaurus lancensis[29]
* Tyrannosaurus lancensis?

* Montana
* Wyoming

Lower to upper Hell Creek Formation.

A few specimens are known

Invalid genus, now recognised as juvenile T. rex.

#### Ornithomimosaurs

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

Ornithomimids reported from the Hell Creek Formation

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

"Orcomimus"

unnamed

* South Dakota[68]

|  |

One partial skeleton.

An ornithomimid. Numem nudum

Struthiomimus[30]

S. sedens[69]

* 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.[69]

Ornithomimus

O. velox[69]

* Montana
* South Dakota
* North Dakota

|  |

Fragmentary specimens

An ornithomimid which was also found in the Denver Formation.

#### Oviraptorosaurs

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 Caenagnathus, Chirostenotes, and Elmisaurus.[29][70][71][72][73] In 2016, an undescribed large-bodied caenagnathid was unearthed in Montana.[74]

Oviraptorosaurs reported from the Hell Creek Formation

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

Anzu[29][70]

A. wyliei[70]

* North Dakota[8][70]
* South Dakota[8][70]

Lower to upper Hell Creek Formation[10]

12 well-preserved specimens[9]

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.[70]

Caenagnathidae

Indeterminate

* Montana

|  |  |

Similar to Citipes and Elmisaurus.

#### Eumaniraptorans

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 disproved in a 2015 study, DePalma et al., when they described the new genus Dakotaraptor, a large species of dromaeosaur.[75] 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[76] and Saurornitholestes[77] 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[75]

A. temertyorum [75]

* Montana[75]
* North Dakota?[7]
* South Dakota?[7]

Lower? to upper Hell Creek Formation[7]

* ROM 63777, a maxilla and tooth[75]
* ROM 63778, a partial dentary[75]
* isolated teeth[75]

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.[75]

Avisaurus[7]

A. archibaldi[7][29]

* Montana[7]

Middle Hell Creek Formation[9]

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

An avisaurid.[7]

cf. A. archibaldi[78]

* Montana[78]

Uppermost Hell Creek Formation[78]

* YPM 57235, a coracoid

An avisaurid tentatively referred to A. archibaldi based on its size.[78]

A. sp.[79]

* Montana[79]

|  |

* distal tarsals, metatarsus (juvenile)[79]

|  |

Brodavis[80]

B. baileyi[80]

* South Dakota[80]

|  |

* UNSM 50665, a left tarsometatarsus missing proximal end, trochleae II and III.[80]

A primitive hesperornithiform.[80]

Dakotaraptor[81]

D. steini [81]

* South Dakota[81]

Upper Hell Creek Formation[81]

* PBMNH.P.10.113.T, a partial skeleton.[81]
* PBMNH.P.10.115.T, a tibia.[81]
* PBMNH.P.10.118.T, an astragalocalcaneum.[81]
* isolated teeth.[81]

A dromaeosaurid. Second-largest dromaeosaurid known.[75]

Paronychodon[82]

P. caperatus [82]

* 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[83][82]

P. bakkeri [83][82]

* 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[80] |

P. skutchi [84]

* Montana[84]

|  |

* UCMP 117605, a tarsometatarsus

A hesperornithiform also found in the Lance Formation.[84]

Richardoestesia [85][86]

R. sp. [85][86]

* 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"[87] | "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"[78]

Unnamed

* Montana[78]

|  |

* YPM 57823, a partial coracoid[78]

An unnamed enantiornithean.[78]

"Unnamed hesperornithiform A"[78]

Unnamed

* Montana

|  |

* UCMP 13355, a tarsometatarsus

A primitive hesperornithiform.[80] The Hell Creek specimen was referred to the same unnamed taxon as RSM P 2315.1 from the Canadian Frenchman Formation.[78] RSM P 2315.1 was later made the holotype of Brodavis americanus.[80] May be a synonym of Potamornis.[78]

"Unnamed ornithurine B"[78]

Unnamed[88]

* Montana[89]

|  |

* UCMP 129143, a partial coracoid[78]

An ornithurine possibly similar to Cimolopteryx[78][88]

"Unnamed ornithurine C"[78]

Unnamed

* Montana[78]
* South Dakota[78]

|  |

* SDSM 64281A, a partial coracoid[78]
* SDSM 64281B, a partial coracoid[78]
* UCMP 175251, a partial coracoid[78]
* MOR 2918, a partial coracoid[78]

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[78]

"Unnamed ornithurine D"[78]

Unnamed

* Montana[78]

|  |

* UCMP 187207, a partial coracoid[78]

An ichthyornithean also present in the Frenchman Formation[78]

## Pterosaurs

Indeterminate azhdarchid remains, most likely belong to Quetzalcoatlus or an unidentified genus, have been found in Hell Creek as well as the Javelina Formation and the Ojo Alamo Formation.[90][91] Indeterminate pteranodontid remains have also been found here as well.[92][93]

Pterosaurs of the Hell Creek Formation

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

Azhdarchidae spp.

Indeterminate

* Montana[90]
* 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, though they are not diagnostic to the generic level.[90]

Pterosaur spp.[94]

Indeterminate

* South Dakota

|  |  |  |

## Crocodylomorphs

Crocodylomorphs reported from the Hell Creek Formation

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

Borealosuchus[95]

* B. sternbergii[95]

* Montana
* North Dakota
* South Dakota

|  |  |

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

Brachychampsa[95]

* B. montana[95]

* Montana
* South Dakota
* North Dakota

|  |  |

Extinct genus of alligatoroid.

Thoracosaurus[95]

* T. neocesariensis[95]

* Montana

|  |  |

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

## Plesiosaurs

Indeterminate plesiosaur remains have been found in Hell Creek.[96]

## Turtles

Turtles reported from the Hell Creek Formation

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

Adocus[97]

Indeterminate[97]

* Montana[98]

|  |  |

Extinct genus of aquatic turtles belonging to the family Adocidae.

Axestemys[99]

A. infernalis[99]

* 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.[100][99]

Compsemys[97]

C. victa[97]

* Montana[98]

|  |  |

A relative of Dermatemydidae.

Peckemys

P. brinkman

* Montana
* North Dakota

|  |  |

A relative of Baenidae.

Emarginachelys

E. cretacea

* Montana

|  |  |

A relative of chelydrids.[101]

Eubaena[97]

E. cephalica[97]

* Montana[98]

|  |  |

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[101]

H. clark[101]

* North Dakota[101]

|  |  |

A kinosternoid related to the Central American river turtle.[101]

Hutchemys[102] | H. walkerorum[102] |

* North Dakota[102]

|  | A shell[102] | A Plastomeninae related to the softshell turtle.[102] |

Plastomenus

P. sp

|  |  |  |

Trionychidae turtle.

Basilemys

B. sinuosa

|  |  |  |

Largest dermatemydid land tortoise.

Trionyx[97]

Indeterminate[97]

* Montana[98]

|  |  |

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[103]

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

Indeterminate mosasaur remains have been unearthed in North Dakota; they may belong to a mosasaur measuring 11 m (36 ft) in length.[104][105]Template:Paleobiota-key-compact

Squamates reported from the Hell Creek Formation

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

Cemeterius[106][107]

C. monstrosus[106][107]

* Montana[106]

|  |  |

A platynotan lizard of uncertain phylogenetic placement, also known from the Lance Formation.[106]

Cerberophis[106][107]

C. robustus[106][107]

* Montana[106]

|  |  |

An alethinophidian snake of uncertain phylogenetic placement.[106]

Obamadon[106][107]

O. gracilis[106][107]

* Montana[106]

|  |  |

A polyglyphanodontian lizard of uncertain phylogenetic placement. Also known from the Lance Formation.[106]

Peneteius[106]

P. aquilonius[106]

* Montana[106]

|  |  |

A chamopsiid polyglyphanodontian lizard.[106]

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.

## Choristoderans

Choristoderans reported from the Hell Creek Formation

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

Champsosaurus[95]

C. laramiensis[95]

* Montana

|  |  |

A champsosaur.

## Mammals

### Multituberculates

Multituberculates reported from the Hell Creek Formation

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

Cimexomys[108]

C. minor[108]

* Montana[108]

|  |  |

A multituberculate of uncertain phylogenetic placement.

Cimolodon[108]

C. nitidus

* Montana
* North Dakota[108]

|  |  |

A cimolodontid multituberculate.

C. cf. nitidus[108]

* South Dakota[108]

|  |  |

A cimolodontid multituberculate.

C. sp.[108]

* North Dakota[108]

|  |  |

A cimolodontid multituberculate.

Cimolomys[108]

C. gracilis

* Montana[108]

|  |  |

A cimolomyid multituberculate.

* C. cf. gracilis[108]

* South Dakota[108]

|  |  |

A cimolomyid multituberculate.

Essonodon[108]

E. browni[108]

* Montana[108]

|  |  |

A cimolomyid multituberculate.

Meniscoessus[108]

M. conquistus

* South Dakota[108]

|  |  |

A cimolomyid multituberculate.

M. robustus

* Montana
* North Dakota
* South Dakota[108]

|  |  |

A cimolomyid multituberculate.

M. cf. robustus

* South Dakota[108]

|  |  |

A cimolomyid multituberculate.

M. sp.

* North Dakota[108]

|  |  |

A cimolomyid multituberculate.

?M. sp.[108]

* North Dakota[108]

|  |  |

A cimolomyid multituberculate.

Mesodma[108]

M. formosa

* Montana
* South Dakota[108]

|  |  |

A neoplagiaulacid multituberculate.

M. cf. formosa

* Montana[108]

|  |  |

A neoplagiaulacid multituberculate.

M. hensleighi

* Montana
* South Dakota[108]

|  |  |

A neoplagiaulacid multituberculate.

M. cf. hensleighi

* South Dakota[108]

|  |  |

A neoplagiaulacid multituberculate.

M. thompsoni

* Montana
* North Dakota
* South Dakota[108]

|  |  |

A neoplagiaulacid multituberculate.

M. cf. thompsoni

* Montana[108]

|  |  |

A neoplagiaulacid multituberculate.

M sp.[108]

* Montana[108]

|  |  |

A neoplagiaulacid multituberculate.

?M sp.[108]

* Montana[108]

|  |  |

A neoplagiaulacid multituberculate.

?Neoplagiaulax[108]

?N. burgessi[108]

* Montana[108]

|  |  |

A neoplagiaulacid multituberculate.

Paracimexomys[108]

P. priscus[108]

* Montana[108]

|  |  |

A multituberculate of uncertain phylogenetic placement.

Paressonodon[109]

P. nelsoni[109]

|  |  |  |

A cimolomyid multituberculate.

Stygimys

S. kuszmauli

* Montana

|  |  |

It was a member of the extinct order Multituberculata.

### Metatherians

Metatherians reported from the Hell Creek Formation

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

Aletridelphys[110][111]

A. florencae

* Montana
* North Dakota
* South Dakota[108]

|  |  |

A pediomyid.

A. hatcheri[110]

* Montana
* South Dakota[108]

|  |  |

A pediomyid.

Alphadon[108]

A. marshi

* Montana
* North Dakota[108]

|  |  |

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[108]

|  |  |

An alphadontid.

A. wilsoni

* Montana[108]

|  |  |

An alphadontid.

A. cf. wilsoni

* Montana[108]

|  |  |

An alphadontid.

A. sp.[108]

* North Dakota
* South Dakota[108]

|  |  |

An alphadontid.

Didelphodon[108]

D. padanicus

* South Dakota[108]

|  |  |

A stagodontid.

D. vorax

* Montana
* North Dakota[108]

|  |  |

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

D. cf. vorax

* South Dakota[108]

|  |  |

A stagodontid.

D. sp.

* North Dakota[108]

|  |  |

A stagodontid.

cf. D. sp.[108]

* North Dakota
* South Dakota[108]

|  |  |

A stagodontid.

Glasbius[108]

G. twitchelli

* Montana[108]

|  |  |

A glasbiid.

G. cf. twitchelli[108]

* Montana[108]

|  |  |

A glasbiid.

Leptalestes[110]

L. cooki

* Montana[108]

|  |  |

A pediomyid.

L. krejcii[110]

* Montana
* South Dakota[108]

|  |  |

A pediomyid.

Nanocuris[109]

N. improvida[109]

|  |  |  |

A deltatheridiid.

Nortedelphys

N. jasoni (= N. intermedius)[109][112]

* Montana
* South Dakota

|  |  |

A herpetotheriid.

Pediomys[108]

P. elegans[108]

* Montana
* South Dakota[108]

|  |  |

A pediomyid.

Protalphadon[108]

P. foxi

* Montana[108]

|  |  |

An alphadontid.

P. lulli[108]

* Montana[108]

|  |  |

An alphadontid.

Turgidodon[108]

T. rhaister[108]

* Montana[108]

|  |  |

An alphadontid.

### Eutherians

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[113]

Alostera[108]

A. saskatchewanensis[108]

* Montana[108]

|  |  |

A eutherian of uncertain phylogenetic placement.

Ambilestes

A. cerberoides

* Montana

|  |  |

A eutherian of uncertain classification, formally a species of Cimolestes

Batodon[108]

B. tenuis[108]

* Montana[108]

|  |  |

A cimolestid eutherian.

Cimolestes[108]

C. incisus

* Montana[108]

|  |  |

A cimolestid eutherian.

C. stirtoni[108]

* Montana[108]

|  |  |

A cimolestid eutherian.

Gypsonictops[108]

G. hypoconus

* Montana
* South Dakota[108]

|  |  |

A gypsonictopsid eutherian.

G. illuminatus

* Montana
* North Dakota[108]

|  |  |

A gypsonictopsid eutherian.

G. cf. illuminatus

* Montana[108]

|  |  |

A gypsonictopsid eutherian.

G. sp.[108]

* Montana[108]

|  |  |

A gypsonictopsid eutherian.

cf. Paranyctoides[108]

cf. Paranyctoides sp.[108]

* Montana[108]

|  |  |

A nyctitheriid eutherian.

Protungulatum[110]

P. coombsi[110]

* Montana[110]

|  |  |

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

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 floodplain 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, Glyptostrobus and cupressaceous conifers; the monocot Limnobiophyllum (a relative of duckweeds); and the dicots Cercidiphyllum and Platanus.[114][115] 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 fruits from the Hell Creek Formation of Spinifructus antiquus of the palm family (Arecaceae), closely related to the genus Astrocaryum.

Dr. Kirk Johnson 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)

* Ferns from Hell Creek

* Cycads are found in Hell Creek

* Ginkgo (uncommon) are found in Hell Creek

* Various angiosperms from Hell Creek

* Monkey-puzzle leaves are found in Hell Creek

* Fossil palm trees indicate a hotter paleoclimate

* Redwood seed cones are known from Hell Creek

* Laurus are found in Hell Creek

* Cercidiphyllum are found in Hell Creek

* Magnolia is commonly found in Hell Creek

Plants of the Hell Creek Formation

* various ferns and cycads.
* Equisetum (Equisetaceae)

Gymnosperms

* Platyspiroxylon (Cupressaceae)
* Podocarpoxylon (Podocarpaceae)
* Elatocladus (Taxodiaceae)
* Sequoiaxylon (Taxodiaceae)
* Taxodioxylon (Taxodiaceae)
* Araucaria (Araucariaceae)
* †Cheirolepidiaceae

Ginkgos

* Baiera
* Ginkgo adiantoides

Angiosperms

* Artocarpus (Moraceae)
* Barberry family (Berberidaceae)
* Cercidiphyllum (Cercidiphyllaceae)
* Dombeyopsis (Sterculiaceae)
* Laurel family (Lauraceae)
* Magnolia (Magnoliaceae)
* Palms (Arecaceae)
* Platanus, sycamore or plane tree (Platanaceae)

Flora of the Hell Creek Formation

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

Aquilapollenites

"Aquilapollenites" attenuatus

|  |  |  |  |

"Aquilapollenites" collaris

|  |  |  |  |

"Aquilapollenites" conatus

|  |  |  |  |

"Aquilapollenites" delicatus

|  |  |  |  |

"Aquilapollenites" marmarthensis

|  |  |  |  |

"Aquilapollenites" quadricretaeus

|  |  |  |  |

"Aquilapollenites" quadrilobus

|  |  |  |  |

"Aquilapollenites" reductus

|  |  |  |  |

"Aquilapollenites" senonicus

|  |  |  |  |

"Aquilapollenites" turbidus

|  |  |  |  |

"Aquilapollenites" striatus

|  |  |  |  |

Alnipollenites

|  |  |  |  |  |

"Ficus"

"Ficus" planicostata

|  |  |  |  |

"Ficus" artocarpoides

|  |  |  |  |

"Ficus" trinervis

|  |  |  |  |

Ilexpollenites

Ilexpollenites compactus

|  |  |  |  |

Interpollis

Interpollis cf. I. supplingensis

|  |  |  |  |

Balmeisporites

Balmeisporites sp.

|  |  |  |  |

Marmarthia

Marmarthia pearsonii

|  |  |  |  |

"Myrica"

"Myrica" torreyi

|  |  |  |  |

Platanites

Platanites marginata

|  |  |  |  |

Sabalites

Sabalites sp.

|  |  |  |  |

Tricolpites

Tricolpites interangulus

|  |  |  |  |

Metasequoia

M. sp

|  |  |  |

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

"Grewiopsis"

"G" saportana

|  |  |  |

Another generic Hamamelididae.

Annona?

A?. robusta

|  |  |  |

Abundant at Brownie Butte, Montana.

Cobbania

C. corrugata

|  |  |  |

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

Araucaria

A. araucana

|  |  |  |

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

Artocarpus

A. lessigiana

|  |  |  |

Abundant at Brownie Butte, Montana.

Celastrus

C. taurenensis

|  |  |  |

Some may be Eucommiacaea.

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.

Cissus

C. marginata

|  |  |  |

Also spelled "marginatus".

Juglans

J. leconteana

|  |  |  |  |

Liriodendrites

L. bradacci

|  |  |  |

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

Liriodendron

L. laramiense

|  |  |  |

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

Leepiesceia

L. presrtocarpoides

|  |  |  |

another laurel.

Marmarthia

M. pearsonii

|  |  |  |

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

M. trivialis

|  |  |  |

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

Platanites

P. marginata

|  |  |  |

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

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.

Vitis

"V." stantonii

|  |  |  |

Possibly a member of the Platanaceae rather than Vitaceae[116][117]

Ziziphus

Z. fibrillosus

|  |  |  |  |

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

indeterminate

|  |  |  |  |

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.

Ginkgo

G. adiantoides

|  |  |  |

The only ginkgo in the Hell Creek Formation; uncommon

Glyptostrobus

G. nordenskioldii

|  |  |  |  |

G. sp

|  |  |  |  |

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.

Marchantia

M. pealii

|  |  |  |  |

Nilssonia

N. yukonensis

|  |  |  |

The only Hell Creek Formation cycadeoid. Uncommon.

Onoclea

O. hesperia

|  |  |  |  |

Paranymphaea

P. hastata

|  |  |  |  |

Platanophyllum

P. montanum

|  |  |  |  |

Porosia

P. verrucosa

|  |  |  |  |

Rhamnus

R. salicifolius

|  |  |  |

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

Sabalites

S. sp

|  |  |  |

Palm tree.

Sapindopsis

S. powelliana

|  |  |  |  |

Sequoites

S. artus

|  |  |  |

Sequoia tree.

Taxodium

T. olrikii

|  |  |  |

Related to today's bald cypress.

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)).

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

|  |  |  |

see above.

Populus

P. nebrascensis

|  |  |  |  |

Cocculus

cf. C. flabella

|  |  |  |  |

Cissites

cf. C. acerifolia

|  |  |  |  |

Pistia

cf. P. corrugata

|  |  |  |

Floating aquatic herb.

Palaeoaster

P. inquirenda

|  |  |  |

A poppy with quite similar seed pods and seeds to that of the extant poppy genus Romneya.

## See also

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

## References

1. ↑ DePalma, Robert; Cichocki, Frederich; Dierick, Manuel; Feeney, Robert (2010). "Preliminary Notes on the First Recorded Amber Insects from the Hell Creek Formation". The Journal of Paleontological Sciences. JPS. C 10: 1–7. https://aaps-journal.org/pdf/JPS-C-10-0001.pdf. Retrieved 16 November 2020.
2. ↑ 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.
3. ↑ Messer, A'ndrea Eluse. "Leaf-mining insects destroyed with the dinosaurs, others quickly appeared". Pennsylvania State University. https://news.psu.edu/story/321434/2014/07/24/research/leaf-mining-insects-destroyed-dinosaurs-others-quickly-appeared.
4. ↑ "North Dakota site shows wreckage from same object that killed the dinosaurs". University of Washington. https://www.washington.edu/news/2019/03/29/north-dakota-site-shows-wreckage-from-same-object-that-killed-the-dinosaurs/.
5. ↑ Peterson, Douglas. "The Day the Dinosaurs Died". The New Yorker. https://www.newyorker.com/magazine/2019/04/08/the-day-the-dinosaurs-died.
6. ↑ 6.0 6.1 6.2 6.3 6.4 Graf, Dan; Cummings, Kevin. "The Mussel Project". The University of Wisconsin-Stevens Point. http://mussel-project.uwsp.edu/fmuotwaolcb/.
7. ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 7.11 7.12 7.13 7.14 7.15 7.16 7.17 7.18 7.19 7.20 7.21 7.22 7.23 7.24 7.25 7.26 7.27 7.28 7.29 7.30 7.31 7.32 7.33 7.34 7.35 7.36 7.37 7.38 7.39 7.40 7.41 7.42 7.43 7.44 7.45 7.46 7.47 7.48 7.49 7.50 7.51 Pearson et al. (2002) p. 154
8. ↑ 8.00 8.01 8.02 8.03 8.04 8.05 8.06 8.07 8.08 8.09 8.10 8.11 8.12 8.13 8.14 8.15 8.16 8.17 8.18 8.19 8.20 8.21 8.22 8.23 8.24 8.25 8.26 8.27 8.28 8.29 8.30 8.31 8.32 8.33 8.34 8.35 Pearson et al. (2002) pp. 145–167
9. ↑ 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 9.10 9.11 9.12 9.13 9.14 9.15 9.16 9.17 Pearson et al. (2002) p. 155
10. ↑ 10.00 10.01 10.02 10.03 10.04 10.05 10.06 10.07 10.08 10.09 10.10 10.11 10.12 10.13 10.14 10.15 10.16 10.17 10.18 Pearson et al. (2002) pp. 156
11. ↑ Listed as "cf. Barbourula sp." in "Class Amphibia," Estes and Berberian, (1970). Page 4.
12. ↑ 12.00 12.01 12.02 12.03 12.04 12.05 12.06 12.07 12.08 12.09 12.10 12.11 12.12 12.13 12.14 12.15 "Class Amphibia," in Estes and Berberian, (1970). Page 4.
13. ↑ 13.0 13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8 "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. ↑ 15.0 15.1 15.2 15.3 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. ↑ 16.00 16.01 16.02 16.03 16.04 16.05 16.06 16.07 16.08 16.09 16.10 16.11 16.12 16.13 16.14 16.15 "Class Osteichthyes," in Estes and Berberian, (1970). Page 3.
17. ↑ 17.0 17.1 17.2 17.3 17.4 17.5 17.6 17.7 "Class Osteichthyes," in Estes and Berberian, (1970). Page 3. All taxa listed occur in Montana, see page 1.
18. ↑ 18.0 18.1 18.2 18.3 "Class Osteichthyes," in Estes and Berberian, (1970). Page 4.
19. ↑ 19.0 19.1 19.2 "Class Osteichthyes," in Estes and Berberian, (1970). Page 4. All taxa listed occur in Montana, see page 1.
20. ↑ 20.0 20.1 Listed as "cf. Paralbula casei" in "Class Osteichthyes," Estes and Berberian, (1970). Page 4.
21. ↑ 21.00 21.01 21.02 21.03 21.04 21.05 21.06 21.07 21.08 21.09 21.10 21.11 21.12 21.13 21.14 21.15 21.16 21.17 21.18 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. Geological Society of America Special Papers. 503. 229–246. doi:10.1130/2014.2503(08). ISBN 978-0-8137-2503-1.
22. ↑ 22.0 22.1 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. doi:10.1017/jpa.2018.92.
23. ↑ 23.0 23.1 "Class Chondrichthyes," in Estes and Berberian, (1970). Page 3.
24. ↑ "Class Chondrichthyes," in Estes and Berberian, (1970). Page 3. All taxa listed occur in Montana, see page 1.
25. ↑ 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. doi:10.2110/palo.2008.p08-030r. Bibcode: 2008Palai..23..645M.
26. ↑ 26.0 26.1 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. https://econtent.unm.edu/digital/collection/bulletins/id/7309.
27. ↑ 27.0 27.1 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. doi:10.1080/02724634.1986.10011619.
28. ↑ Carpenter, K. (1 November 2002). "Late Cretaceous dinosaurs from the Denver Basin, Colorado". Rocky Mountain Geology 37 (2): 237–254. doi:10.2113/11. http://doc.rero.ch/record/14415/files/PAL_E1598.pdf.
29. ↑ 29.00 29.01 29.02 29.03 29.04 29.05 29.06 29.07 29.08 29.09 29.10 29.11 29.12 29.13 29.14 29.15 29.16 29.17 29.18 29.19 29.20 29.21 29.22 29.23 29.24 29.25 29.26 29.27 29.28 29.29 29.30 29.31 29.32 29.33 29.34 29.35 29.36 29.37 29.38 29.39 29.40 29.41 29.42 "Dinosaur distribution (Late Cretaceous; North America; Montana)." Weishampel, et al. (2004). Page 584.
30. ↑ 30.00 30.01 30.02 30.03 30.04 30.05 30.06 30.07 30.08 30.09 30.10 "Dinosaur distribution (Late Cretaceous; North America; South Dakota)." Weishampel, et al. (2004). Page 586.
31. ↑ 31.0 31.1 31.2 31.3 "Dinosaur distribution (Late Cretaceous; North America; North Dakota)." Weishampel, et al. (2004). Page 585.
32. ↑ Giffin, Emily B.; Gabriel, Diane L.; Johnson, Rolf E. (22 January 1988). "A New Pachycephalosaurid Hell Creek Formation of Montana". Journal of Vertebrate Paleontology 7 (4): 398–407. doi:10.1080/02724634.1988.10011672.
33. ↑ 33.0 33.1 33.2 33.3 Bakker et al. (2006)
34. ↑ 34.0 34.1 34.2 34.3 34.4 Horner, John R.; Goodwin, Mark B.; Evans, David C. (2023-04-14). "A new pachycephalosaurid from the Hell Creek Formation, Garfield County, Montana, U.S.A.". Journal of Vertebrate Paleontology 42 (4): e2190369. doi:10.1080/02724634.2023.2190369. ISSN 0272-4634.
35. ↑ 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:ANGODP2.0.CO;2].
36. ↑ "Table 21.1," in Weishampel, et al. (2004). Page 465.
37. ↑ Carpenter, Kenneth (2006). Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Bloomington, IN: Indiana University Press. ISBN 978-0253348173. https://muse.jhu.edu/book/49401. Retrieved 13 November 2020.
38. ↑ Ryan, Michael J.; Chinnery-Allgeier, Brenda J.; Eberth, David A. (2010). New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium. Indiana University Press. ISBN 978-0-253-35358-0.
39. ↑ Scannella, John B.; Fowler, Denver W. (2014). "A stratigraphic survey of Triceratops localities in the Hell Creek Formation, northeastern Montana (2006–2010)". Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas. doi:10.1130/2014.2503(12).
40. ↑ Scannella, B.; Fowler, W.; Goodwin, B.; Horner, R. (2014). Evolutionary Trends in Triceratops from the Hell Creek Formation, Montana (Project). doi:10.7934/p1099.
41. ↑ Scannella, John (10 November 2020). "A chasmosaurine ceratopsid premaxilla from the basal sandstone of the Hell Creek Formation, Montana". Vertebrate Anatomy Morphology Palaeontology 8: 154–169. doi:10.18435/vamp29366.
42. ↑ Biles, Jan. "Rare dinosaur skull being prepared for exhibition". Topeka Capital-Journal. http://cjonline.com/news-local/2015-09-07/rare-dinosaur-skull-being-prepared-exhibition.
43. ↑ "Super-sized Ceratopsian Skull Might be New Species". 29 August 2015. https://blog.everythingdinosaur.co.uk/blog/_archives/2015/08/29/super-sized-ceratopsian-skull-might-be-new-species.html.
44. ↑ O' Connell, Max. "Dinosaur skull found in Buffalo likely a new species". http://rapidcityjournal.com/news/local/dinosaur-skull-found-in-buffalo-likely-a-new-species/article_b33d3375-b74c-5941-aa0b-281ad59b430a.html.
45. ↑ Ostrom, John H. (May 1978). "Leptoceratops gracilis from the 'Lance' Formation of Wyoming". Journal of Paleontology 52 (3): 697–704.
46. ↑ 46.0 46.1 46.2 Christopher J. Ott and Peter L. Larson, 2010, "A New, Small Ceratopsian Dinosaur from the Latest Cretaceous Hell Creek Formation, Northwest South Dakota, United States: A Preliminary Description", In: Ryan, M.J., Chinnery-Allgeier, B.J., and Eberth, D.A. (eds.) New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium, Bloomington, Indiana University Press, 656 pp.
47. ↑ Nicholas R. Longrich (2011). "Titanoceratops ouranous, a giant horned dinosaur from the Late Campanian of New Mexico". Cretaceous Research 32 (3): 264–276. doi:10.1016/j.cretres.2010.12.007.
48. ↑ Scannella, J.; 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.
49. ↑ Mallon, Jordan C; Holmes, Robert B; Bamforth, Emily L; Schumann, Dirk (7 May 2022). "The record of Torosaurus (Ornithischia: Ceratopsidae) in Canada and its taxonomic implications". Zoological Journal of the Linnean Society 195 (1): 157–171. doi:10.1093/zoolinnean/zlab120.
50. ↑ Forster, Catherine A. (2016). "Taxomomic validity of the ceratopsid dinosaur Ugrosaurus olsoni (Cobabe and Fastovsky)". Journal of Paleontology 67 (2): 316–318. doi:10.1017/S0022336000032273. ISSN 0022-3360.
51. ↑ 51.0 51.1 Scannella, John B.; Fowler, Denver W.; Goodwin, Mark B.; Horner, John R. (2014-07-15). "Evolutionary trends in Triceratops from the Hell Creek Formation, Montana". Proceedings of the National Academy of Sciences of the United States of America 111 (28): 10245–10250. doi:10.1073/pnas.1313334111. ISSN 0027-8424. PMID 24982159. Bibcode: 2014PNAS..11110245S.
52. ↑ 52.0 52.1 Campione, N.E.; 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. PMID 21969872. Bibcode: 2011PLoSO...625186C.
53. ↑ Manning, Phillip L.; Morris, Peter M.; McMahon, Adam; Jones, Emrys; Gize, Andy; Macquaker, Joe H. S.; Wolff, George; Thompson, Anu et al. (7 October 2009). "Mineralized Soft-Tissue Structure and Chemistry in a Mummified Hadrosaur from the Hell Creek Formation, North Dakota (USA)". Proceedings: Biological Sciences 276 (1672): 3429–3437. doi:10.1098/rspb.2009.0812. PMID 19570788.
54. ↑ Vajda, Vivi; Lyson, Tyler R.; Bercovici, Antonie; Doman, Jessman H.; Pearson, Dean A. (November 2013). "A snapshot into the terrestrial ecosystem of an exceptionally well-preserved dinosaur (Hadrosauridae) from the Upper Cretaceous of North Dakota, USA". Cretaceous Research 46: 114–122. doi:10.1016/j.cretres.2013.08.010. http://urn.kb.se/resolve?urn=urn:nbn:se:nrm:diva-1409.
55. ↑ Rohrer, W. L.; Konizeski, R. (May 1960). "On the Occurrence of Edmontosaurus in the Hell Creek Formation of Montana". 34 34 (3): 464–466.
56. ↑ 56.0 56.1 Wosik, Mateusz; Goodwin, Mark B.; Evans, David C. (2 November 2017). "A nestling-sized skeleton of Edmontosaurus (Ornithischia, Hadrosauridae) from the Hell Creek Formation of northeastern Montana, U.S.A., with an analysis of ontogenetic limb allometry". Journal of Vertebrate Paleontology 37 (6): e1398168. doi:10.1080/02724634.2017.1398168. https://figshare.com/articles/journal_contribution/5899300.
57. ↑ 57.0 57.1 Listed as "?Thescelosaurus garbanii" in "Dinosaur distribution (Late Cretaceous; North America; Montana)." Weishampel, et al. (2004). Page 584.
58. ↑ 58.0 58.1 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. doi:10.1671/039.029.0328.
59. ↑ Noted as being present, although misspelled as "Thescelosaurus garbani, in " "Dinosaur distribution (Late Cretaceous; North America; South Dakota)." Weishampel, et al. (2004). Page 586.
60. ↑ Boyd, Brown, et al. (2009)
61. ↑ Galton, Peter M. (September 1974). "Notes on Thescelosaurus, a Conservative Ornithopod Dinosaur from the Upper Cretaceous of North America, with Comments on Ornithopod Classification". Journal of Paleontology 48 (5): 1048–1067.
62. ↑ Manning, Phillip L.; Ott, Christopher; Falkingham, Peter L. (September–October 2008). "A Probable Tyrannosaurid Track from the Hell Creek Formation (Upper Cretaceous), Montana, United States". PALAIOS 23 (9/10): 645–647. doi:10.2110/palo.2008.p08-030r. Bibcode: 2008Palai..23..645M.
63. ↑ Dalman, S.G.; Lucas, S.G.. "A new large Tyrannosaurid Alamotyrannus brinkmani, n. gen., n. sp. (Theropoda: Tyrannosauridae), from the Upper Cretaceous Ojo Alamo Formation (Naashoibito Member), San Juan Basin, New Mexico". New Mexico Museum of Natural History and Science Bulletin.
64. ↑ Molnar, R.E. (January 1980). "An Albertosaur from the Hell Creek Formation of Montana". Journal of Paleontology 54 (1): 102–108.
65. ↑ Molnar, R. E. (January 1978). "A New Theropod Dinosaur from the Upper Cretaceous of Central Montana". Journal of Paleontology 52 (1): 73–82.
66. ↑ Hutchinson and Chiappe, 1998. The first known alvarezsaurid (Theropoda: Aves) from North America. Journal of Vertebrate Paleontology. 18(3), 447–450.
67. ↑ Horner, John R.; Goodwin, Mark B.; Myhrvold, Nathan (2011-02-09). "Dinosaur Census Reveals Abundant Tyrannosaurus and Rare Ontogenetic Stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA" (in en). PLOS ONE 6 (2): e16574. doi:10.1371/journal.pone.0016574. ISSN 1932-6203. PMID 21347420. Bibcode: 2011PLoSO...616574H.
68. ↑ 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
69. ↑ 69.0 69.1 69.2 Longrich (2008), pages 983–996.
70. ↑ 70.0 70.1 70.2 70.3 70.4 70.5 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. PMID 24647078. Bibcode: 2014PLoSO...992022L.
71. ↑ Stein, Walter W. (2019). "TAKING COUNT: A Census of Dinosaur Fossils Recovered From the Hell Creek and Lance Formations (Maastrichtian).". The Journal of Paleontological Sciences 8: 1–42. https://www.aaps-journal.org/pdf/JPS.C.2019.01a.pdf.
72. ↑ Schachner, Emma; Larson, Tyler; Hanks, Harold. A preliminary report of a new specimen of Chirostenotes (Oviraptorosauria: Theropoda) from the Hell Creek Formation of North Dakota. in "Abstracts of Papers". Journal of Vertebrate Paleontology 26: 1–152. 2006. doi:10.1080/02724634.2006.10010069.
73. ↑ Russel, Dale A.; Manabe, Makoto (2002). "Synopsis of the Hell Creek (uppermost Cretaceous) dinosaur assemblage.". Geological Society of America Special Papers 361: 169–176. ISBN 9780813723617. https://books.google.com/books?id=cHvcIeh2f84C&dq=Hell+Creek+Chirostenotes&pg=PA169. Retrieved 18 October 2020.
74. ↑ Benner, Elizabeth K. C.; Cullen, T. M.; Evans, D. C. (May 18–21, 2016). "MORPHOLOGICAL AND HISTOLOGICAL ANALYSIS OF A NEW LARGE-BODIED 10 CAENAGNATHID SPECIMEN (THEROPODA: OVIRAPTOROSAURIA) FROM THE HELL CREEK FORMATION (MONTANA)". Canadian Society of Vertebrate Paleontology: 17–18. https://cansvp.files.wordpress.com/2013/08/csvp-2016-abstract-book-compressed.pdf. Retrieved 17 November 2020.
75. ↑ 75.0 75.1 75.2 75.3 75.4 75.5 75.6 75.7 75.8 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): 1041–9. doi:10.1007/s00114-013-1107-5. PMID 24248432. Bibcode: 2013NW....100.1041E.
76. ↑ Russel, Dale A.; Manabe, Makoto (2002). "Synopsis of the Hell Creek (uppermost Cretaceous) dinosaur assemblage.". Geological Society of America Special Papers 361: 169–176. ISBN 9780813723617. https://books.google.com/books?id=cHvcIeh2f84C&dq=Hell+Creek+Dromaeosaurus&pg=PA169. Retrieved 23 October 2020.
77. ↑ Dinosaur distribution (Late Cretaceous; North America; North Dakota). Weishampel, et al. (2004). Page 585
78. ↑ 78.00 78.01 78.02 78.03 78.04 78.05 78.06 78.07 78.08 78.09 78.10 78.11 78.12 78.13 78.14 78.15 78.16 78.17 78.18 78.19 78.20 78.21 78.22 78.23 78.24 78.25 Longrich, N.R.; Tokaryk, T.; 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. PMID 21914849. Bibcode: 2011PNAS..10815253L.
79. ↑ 79.0 79.1 79.2 Stidham, 1999. North American avisaurids (Aves: Enantiornithes): New data on morphology and phylogeny. VII International Symposium on Mesozoic Terrestrial Ecosystems, abstracts.
80. ↑ 80.0 80.1 80.2 80.3 80.4 80.5 80.6 80.7 Larry D. Martin; Evgeny N. Kurochkin; Tim T. Tokaryk (2012). "A new evolutionary lineage of diving birds from the Late Cretaceous of North America and Asia". Palaeoworld 21: 59–63. doi:10.1016/j.palwor.2012.02.005.
81. ↑ 81.0 81.1 81.2 81.3 81.4 81.5 81.6 81.7 Bakker, Robert T.; Larson, Peter L.; Martin, Larry D.; Burnham, David A.; DePalma, Robert A. (30 October 2015). "The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation". Paleontological Contributions 14: 1–16. doi:10.17161/paleo.1808.18764.
82. ↑ 82.0 82.1 82.2 82.3 Olshevsky, G., 1991, A Revision of the Parainfraclass Archosauria Cope, 1869, Excluding the Advanced Crocodylia. Mesozoic Meanderings 2 pp 196
83. ↑ 83.0 83.1 Carpenter, K. (1982). "Baby dinosaurs from the Late Cretaceous Lance and Hell Creek formations and a description of a new species of theropod". Contributions to Geology, University of Wyoming 20 (2): 123–134. http://doc.rero.ch/record/232469/files/PAL_E4465.pdf.
84. ↑ 84.0 84.1 84.2 Elzanowski, A.; Paul, G.S.; Stidham, T.A. (2001). "An avian quadrate from the Late Cretaceous Lance Formation of Wyoming". Journal of Vertebrate Paleontology 20 (4): 712–719. doi:10.1671/0272-4634(2000)020[0712:aaqftl2.0.co;2].
85. ↑ 85.0 85.1 Estes, Richard (1964). Fossil vertebrates from the late Cretaceous Lance formation, eastern Wyoming. University of California Press. OCLC 3753287. [page needed]
86. ↑ 86.0 86.1 Larson, Derek W.; Currie, Philip J. (23 January 2013). "Multivariate Analyses of Small Theropod Dinosaur Teeth and Implications for Paleoecological Turnover through Time". PLOS ONE 8 (1): e54329. doi:10.1371/journal.pone.0054329. PMID 23372708. Bibcode: 2013PLoSO...854329L.
87. ↑ Stidham, Thomas Allen (2001). The origin and ecological diversification of modern birds: Evidence from the extinct wading ducks, Presbyornithidae (Neornithes: Anseriformes) (Thesis). OCLC 892837810. ProQuest 304684225.
88. ↑ 88.0 88.1 "Class Aves," in Estes and Berberian, (1970). Page 7.
89. ↑ "Class Aves," in Estes and Berberian, (1970). Page 7. All taxa listed occur in Montana, see page 1.
90. ↑ 90.0 90.1 90.2 Henderson, Michael; Peterson, Joseph (30 March 2006). "An Azhdarchid Pterosaur Cervical Vertebra from the Hell Creek Formation (Maastrichtian) of Southeastern Montana". Journal of Vertebrate Paleontology 26 (1): 192–195. doi:10.1671/0272-4634(2006)26[192:AAPCVF2.0.CO;2]. http://doc.rero.ch/record/15687/files/PAL_E2073.pdf.
91. ↑ Averianov, Alexander (11 August 2014). "Review of taxonomy, geographic distribution, and paleoenvironments of Azhdarchidae (Pterosauria)". ZooKeys (432): 1–107. doi:10.3897/zookeys.432.7913. PMID 25152671.
92. ↑ Longrich, Nicholas; Martill, David; Andres, Brian (13 March 2018). "Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary". PLOS Biology 16 (3): e2001663. doi:10.1371/journal.pbio.2001663. PMID 29534059.
93. ↑ Longrich, Nicholas; Martill, David; Andres, Brian (11 April 2018). "Correction: Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary". PLOS Biology 16 (4): e1002627. doi:10.1371/journal.pbio.1002627. PMID 29641516.
94. ↑ "New Hell Creek Pterosaur Species". http://trieboldpaleontology.com/hellcreekpterosaur.html.
95. ↑ 95.0 95.1 95.2 95.3 95.4 95.5 95.6 95.7 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. http://revistas.ucm.es/index.php/JIGE/article/view/33860.
96. ↑ DePalma, 2010
97. ↑ 97.0 97.1 97.2 97.3 97.4 97.5 97.6 97.7 "Order Testudinata," in Estes and Berberian, (1970). Page 5.
98. ↑ 98.0 98.1 98.2 98.3 "Order Testudinata," in Estes and Berberian, (1970). Page 5. All taxa listed occur in Montana, see page 1.
99. ↑ 99.0 99.1 99.2 Walter G. Joyce; Donald B. Brinkman; Tyler R. Lyson (2019). "A new species of trionychid turtle, Axestemys infernalis sp. nov., from the Late Cretaceous (Maastrichtian) Hell Creek and Lance formations of the Northern Great Plains, USA". Palaeontologia Electronica 22 (3): Article number 22.3.72. doi:10.26879/949.
100. ↑ Arbour, Victoria M.; Zanno, Lindsay E.; Larson, Derek W.; Evans, David C.; Sues, Hans-Dieter (9 February 2016). "The furculae of the dromaeosaurid dinosaur Dakotaraptor steini are trionychid turtle entoplastra". PeerJ 4: e1691. doi:10.7717/peerj.1691. PMID 26893972.
101. ↑ 101.0 101.1 101.2 101.3 101.4 Georgia E. Knauss; Walter G. Joyce; Tyler R. Lyson; 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.
102. ↑ 102.0 102.1 102.2 102.3 102.4 "Cretaceous-Period Softshell Turtle Lived alongside Giant Dinosaurs | Sci-News.com" (in en-US). 14 March 2022. http://www.sci-news.com/paleontology/hutchemys-walkerorum-10616.html.
103. ↑ Tyler R. Lyson; Jacob L. Sayler; Walter G. Joyce (2019). "A new baenid turtle, Saxochelys gilberti, gen. et sp. nov., from the uppermost Cretaceous (Maastrichtian) Hell Creek Formation: sexual dimorphism and spatial niche partitioning within the most speciose group of Late Cretaceous turtles". Journal of Vertebrate Paleontology 39 (4): e1662428. doi:10.1080/02724634.2019.1662428. https://figshare.com/articles/dataset/A_new_baenid_turtle_i_Saxochelys_gilberti_i_gen_et_sp_nov_from_the_uppermost_Cretaceous_Maastrichtian_Hell_Creek_Formation_sexual_dimorphism_and_spatial_niche_partitioning_within_the_most_speciose_group_of_Late_Cretaceous_turtles/9944129.
104. ↑ "Fossils may capture the day the dinosaurs died. Here's what you should know." (in en). 2019-03-31. https://www.nationalgeographic.com/science/article/fossils-found-from-day-dinosaurs-died-chicxulub-tanis-cretaceous-extinction.
105. ↑ Van Vranken, Nathan E.; Boyd, Clint A. (2021-08-19). "The first in situ collection of a mosasaurine from the marine Breien Member of the Hell Creek Formation in south-central North Dakota, USA" (in en). PaleoBios 38. doi:10.5070/P938054460. ISSN 0031-0298. https://escholarship.org/content/qt8v08w2d6/qt8v08w2d6.pdf.
106. ↑ 106.00 106.01 106.02 106.03 106.04 106.05 106.06 106.07 106.08 106.09 106.10 106.11 106.12 106.13 106.14 106.15 Nicholas R. Longrich; Bhart-Anjan S. Bhullar; 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. PMID 23236177. Bibcode: 2012PNAS..10921396L.
107. ↑ 107.0 107.1 107.2 107.3 107.4 107.5 Nicholas R. Longrich; Bhart-Anjan S. Bhullar; 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. Bibcode: 2013PNAS..110Q6608..
108. ↑ 108.00 108.01 108.02 108.03 108.04 108.05 108.06 108.07 108.08 108.09 108.10 108.11 108.12 108.13 108.14 108.15 108.16 108.17 108.18 108.19 108.20 108.21 108.22 108.23 108.24 108.25 108.26 108.27 108.28 108.29 108.30 108.31 108.32 108.33 108.34 108.35 108.36 108.37 108.38 108.39 108.40 108.41 108.42 108.43 108.44 108.45 108.46 108.47 108.48 108.49 108.50 108.51 108.52 108.53 108.54 108.55 108.56 108.57 108.58 108.59 108.60 108.61 108.62 108.63 108.64 108.65 108.66 108.67 108.68 108.69 108.70 108.71 108.72 108.73 108.74 108.75 108.76 108.77 108.78 108.79 108.80 108.81 108.82 108.83 108.84 108.85 108.86 108.87 108.88 108.89 108.90 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
109. ↑ 109.0 109.1 109.2 109.3 109.4 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.
110. ↑ 110.0 110.1 110.2 110.3 110.4 110.5 110.6 J. David Archibald; Yue Zhang; Tony Harper; 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.
111. ↑ Davis, B. M. (2007). "A revision of 'pediomyid' marsupials from the Late Cretaceous of North America". Acta Palaeontologica Polonica 2 (52). https://www.infona.pl/resource/bwmeta1.element.agro-article-dd7126e7-9923-4ef2-870f-f8f654995651.
112. ↑ Thomas E. Williamson; Stephen L. Brusatte; Thomas D. Carr; Anne Weil; 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.
113. ↑ Fox, Richard C. (December 2015). "A revision of the Late Cretaceous–Paleocene eutherian mammal Cimolestes Marsh, 1889". Canadian Journal of Earth Sciences 52 (12): 1137–1149. doi:10.1139/cjes-2015-0113. Bibcode: 2015CaJES..52.1137F.
114. ↑ Chandrasekharam, A., 1974. Megafossil flora from the Genesee locality, Alberta, Canada. Palaeontographica, Abt. A, Band 174
115. ↑ Christophel, D.C., 1976. Fossil floras from the Smoky Tower locality, Alberta, Canada. Palaeontographica, Abt. B, Band 157
116. ↑ Johnson, Kirk R. (2002). "Megaflora of the Hell Creek and lower Fort Union Formations in the western Dakotas: Vegetational response to climate change, the Cretaceous-Tertiary boundary event, and rapid marine transgression". The Hell Creek Formation and the Cretaceous-Tertiary Boundary in the Northern Great Plains: An Integrated Continental Record of the End of the Cretaceous. doi:10.1130/0-8137-2361-2.329. ISBN 9780813723617.
117. ↑ Arens, Nan Crystal; Allen, Sarah E. (1 January 2014). "A florule from the base of the Hell Creek Formation in the type area of eastern Montana: Implications for vegetation and climate". Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas. doi:10.1130/2014.2503(06). ISBN 9780813725031.

### Bibliography

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* Johnson, K.R.; D.J. Nichols, and J.H. Hartman. 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.

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* 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\. 983–996. doi:10.1111/j.1475-4983.2008.00791.x
* Manning, P.L.; C. Ott, and P.L. Falkingham. 2008. The first tyrannosaurid track from the Hell Creek Formation (Late Cretaceous), Montana, U.S.A. PALAIOS 23\. 645–647. doi:10.2110/palo.2008.p08-030r Bibcode: 2008Palai..23..645M
* Bakker, R.T.; R.M. Sullivan; V. Porter; P. Larson, and S.J. Saulsbury. 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\. 331–354. Accessed 1907-10-31.
* Henderson, M.D., and J.E. Peterson. 2006. [192:AAPCVF2.0.CO;2 An azhdarchid pterosaur cervical vertebra from the Hell Creek Formation (Maastrichtian) of southeastern Montana]. Journal of Vertebrate Paleontology 26\. 192–195.
* Weishampel, David B.; Peter Dodson, and Halszka Osmólska (eds.). 2004. The Dinosauria, 2nd edition, 1–880. Berkeley: University of California Press. Accessed 2019-02-21. ISBN:0-520-24209-2
* Pearson, D.A.; T. Schaefer; K.R. Johnson; D.J. Nichols, and J.P. Hunter. 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. Accessed 2019-03-22. ISBN 9780813723617
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* Christophel, D.C.. 1976. Fossil floras from the Smoky Tower locality, Alberta, Canada. Palaeontographica, Abt. B 157\. x.
* Chandrasekharam, A.. 1974. Megafossil flora from the Genesee locality, Alberta, Canada. Palaeontographica, Abt. A 174\. x.
* Estes, R., and P. Berberian. 1970. Paleoecology of a late Cretaceous vertebrate community from Montana. Breviora 343\. 1.

## External links

* 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

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