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

Invertebrates

Insects like 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]

Invertebrates
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
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

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Amphibians reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

Anura (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]

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]

Habrosaurus[7][12]

H. dilatus[7][12]

Middle to upper Hell Creek Formation[9]

6 specimens[10]

Habrosaurus is a sirenid amphibian.[7]

Lisserpeton[12]

L. bairdi[12]

Opisthotriton[7][12]

O. kayi[7][12]

Lower to upper Hell Creek Formation[9]

22 specimens[10]

Opisthotriton is classified as a Batrachosauroididae.[7]

Paranecturus[15]

P. garbanii[15]

A member of Proteidae.[15]

Proamphiuma[12]

P. cretacica[12]

Prodesmodon[12]

P. copei[12]

Scapherpeton[7][12]

S. tectum[7][12]

Lower to upper Hell Creek Formation[9]

144 specimens[10]

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

Scotiophryne[12]

S. pustulosa[12]

A small frog

Fish

Bony fish

Bony fishes
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Acipenser[7][16][17] A. amnisinferos[17] A sturgeon
A. eruciferus[16]
A. praeparatorum[17]
  • North Dakota (Tanis)[17]
A. cf. A. amnisinferos[17]
  • North Dakota (Tanis)[17]

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]
Anchiacipencer[19] A. acanthaspis[19] A sturgeon, originally considered as indeterminate material[19]
Belonostomus[7][16] B. longirostris[7][16] Lower to upper Hell Creek Formation[9] 28 specimens[10] A long-snouted slender fish classified as an aspidorhynchid.[7]
Coriops[20] C. amnicolus[20]

Cyclurus[16]

C. fragosus[16]

A small amiid fish (ubiquitous). Previously known as Amia fragosa or Kindleia fragosa.[22] 2610 specimens have been assigned to Kindleia, making it an extremely common genus.[10]
Cyclurus kehreri from Messel Pit, species within same genus as C. fragosus
"Lepisosteus"[7][16] "L. occidentalis"[7][16] Lower to uppermost Hell Creek Formation[9] 938 specimens are assigned to Lepidosteus[10] A lepidosteid that is very common in the Hell Creek Formation.[7] Nomen dubium.[23]
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]
Paleopsephurus[16] P. wilsoni[16] A paddlefish
Paralbula[24] P. casei[24]
Parapsephurus[25] P. willybemisi[25]
  • North Dakota (Tanis)[25]
 A paddlefish
Platacodon[20] P. nanus[20] Small teleost fish
Protamia[16] Indeterminate[16]
Pachyrhizodontoidei Indeterminate Fish
Polyodontidae[26] Indeterminate[26] Paddlefish
Protoscaphirhynchus[16] P. squamosus[16] A sturgeon
Pugiopsephurus[25] P. inundatus[25]
  • North Dakota (Tanis)[25]
 A paddlefish


Cartilaginous fish

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

Chiloscyllium[27]

C. sp.[27]

A member of Hemiscylliidae.[27]

Galagadon[28]

G. nordquistae
  • South Dakota

Isolated teeth

A carpet shark

Lonchidion[29]

L. selachos[29]

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[27]

M. pustulosus[27]

Lower to upper Hell Creek Formation.[9]

1677 specimens[10] previously assigned to M. bipartitus.[27]

Is an anacoracid batoid[7] rajiform related to guitarfishes.[27] Described on the basis of teeth formerly assigned to the species M. bipartitus.[27] The material assigned to Myledaphus bipartitus and makes up 16.5% of the vertebrate remains.[7]

Protoginglymostoma[27]

P. estesi[27]

A member of Ginglymostomatidae.[27] Formerly assigned to the genus Brachaelurus.

Restesia[27]

R. americana[27]

Middle Hell Creek Formation[9]

5 specimens previously assigned to Squatirhina[10]

A wobbegong-like shark.[27] Formerly assigned to Squatirhina. The remains consist of 0.05% of the vertebrates.[10] Also known from the Lance Formation.[27]

Carcharhinidae indet.[28]

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.[31]

  • 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.[32] 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.[33]

Ornithischians

Ankylosaurs

Indeterminate nodosaur remains have been unearthed in the Hell Creek Formation and other nearby areas.[34][35]

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

Ankylosaurus[36]

A. magniventris[36]

 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[36]

D. schlessmani[36]

 Skull roof, pelvis and osteoderms.

A nodosaurid ankylosaur whose remains have been found in the Lance and Laramie Formation.[34]

Pachycephalosaurs

An undescribed and unnamed pachycephalosaur is present in North Dakota.[38] 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.[39]

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

Dracorex[40]

D. hogwartsia[40]

A pachycephalosaur, possibly synonymous with Pachycephalosaurus.

Pachycephalosaurus[36]

P. wyomingensis[36]

A pachycephalosaur. Also found in the Lance Formation.

Platytholus[41] P. clemensi[41] A partial skull[41] A medium-sized pachycephalosaurine closely related to Acrotholus and Prenocephale

Sphaerotholus[36]

S. buchholtzae[36]

"Skull material."[44]

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[43]

A left squamosal.[43]

A pachycephalosaur distinguished from S. buchholtzae by its more ornamented squamosal.[43]

Stygimoloch[36]

S. spinifer[36]
  • Montana[36]
  • 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.[45][46][47][48][49] 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.[50][51][52]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Ceratopsians reported from the Hell Creek Formation
Genus Species Synonyms State Stratigraphic position Material Notes Images

Leptoceratops[36]

L. gracilis[36]

A small primitive-looking ceratopsian. Fossils have also been found in the Lance Formation in Wyoming.[53]

Tatankaceratops[54]

T. sacrisonorum[54]

A controversial ceratopsian possibly synonymous with Triceratops[55]

Torosaurus[7][36]

T. latus[7][36]

Upper Hell Creek Formation[9]

A ceratopsian that was once proposed to be synonymous with Triceratops,[56] but is now regarded as a valid and distinct ceratopsian.[57] 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][36]

T. horridus[7][36]

Lowermost to the middle Hell Creek Formation[59]

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[36]
  • Montana[36]
  • South Dakota
 Upper 1/3 of the Hell Creek Formation[59]

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[60]
  • Anatotitan copei[60]

Very common.

A hadrosaur. Also found in the Denver, Frenchman, Lance, Laramie, and Scollard Formations.[63][64] Hatchlings have also been unearthed.[64]

Thescelosaurus[37]

T. garbanii[65][66]
  • Bugenasaura garbanii[66]

T. neglectus[7][37]

Lower to upper Hell Creek Formation[9]

50 specimens[10]

A small thescelosaurine. Also found in the Frenchman, Lance, Laramie, and Scollard Formations.[68] Two species are known from Hell Creek; T. neglectus and T. garbanii.[69]

Theropods

Theropod tracks have been found in South Dakota.[37] A trackway from South Dakota, named Wakinyantanka, was made by a mid-sized theropod with three slender toes, possibly a small tyrannosaurid.[33] 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.[70] 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.[71][72] Theropod remains are very common in Hell Creek, some of which belong to indeterminate species on maniraptorans.[73]

Alvarezsaurs

Alvarezsaurs reported from the Hell Creek Formation
Genus Species Synonyms State Stratigraphic position Material Notes Images
"Ornithomimus" "O." minutus

Trierarchuncus[36]

T. prairiensis[36]

upper Hell Creek Formation.

An alvarezsaur known from a partial post-cranial skeleton.[74]

Tyrannosaurids

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

Tyrannosaurus[7][36]

T. rex[7][36]

Lower to upper Hell Creek Formation.

A tyrannosaur, known from several specimens including a juvenile nicknamed "Jane".[75] 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][36]

N.lancensis[7][36]
  • Stygivenator?
  • Deinodon lancensis
  • Albertosaurus lancensis[36]
  • 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]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Ornithomimids reported from the Hell Creek Formation
Genus Species State Stratigraphic position Material Notes Images

"Orcomimus"

unnamed

One partial skeleton.

An ornithomimid. Numem nudum

Struthiomimus[37]

S. sedens[77]
  • 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.[77]

Ornithomimus

O. velox[77]
  • 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.[36][78][79][80][81] In 2016, an undescribed large-bodied caenagnathid was unearthed in Montana.[82]

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[36][78]

A. wyliei[78]

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.[78]

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.[83] 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[84] and Saurornitholestes[85] 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[83]

A. temertyorum [83]

Lower? to upper Hell Creek Formation[7]
  • ROM 63777, a maxilla and tooth[83]
  • ROM 63778, a partial dentary[83]
  • isolated teeth[83]

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.[83]

Avisaurus[7]

A. archibaldi[7][36]

Middle Hell Creek Formation[9]
  • UCMP 117600, holotype, a tarsometatarsus
  • PU 17324, a tarsometatarsus

An avisaurid.[7]

cf. A. archibaldi[86]

Uppermost Hell Creek Formation[86]
  • YPM 57235, a coracoid

An avisaurid tentatively referred to A. archibaldi based on its size.[86]

A. sp.[87]
  • distal tarsals, metatarsus (juvenile)[87]

Brodavis[88]

B. baileyi[88]
  • UNSM 50665, a left tarsometatarsus missing proximal end, trochleae II and III.[88]

A primitive hesperornithiform.[88]

Dakotaraptor[89]

D. steini [89]

Upper Hell Creek Formation[89]
  • PBMNH.P.10.113.T, a partial skeleton.[89]
  • PBMNH.P.10.115.T, a tibia.[89]
  • PBMNH.P.10.118.T, an astragalocalcaneum.[89]
  • isolated teeth.[89]

A dromaeosaurid. Second-largest dromaeosaurid known.[83]

Paronychodon[90]

P. caperatus [90]
  • 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[91][90]

P. bakkeri [91][90]
  • 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[88]

P. skutchi [92]
  • UCMP 117605, a tarsometatarsus

A hesperornithiform also found in the Lance Formation.[92]

Richardoestesia [93][94]

R. sp. [93][94]
  • 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"[95] "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"[86]

Unnamed
  • YPM 57823, a partial coracoid[86]

An unnamed enantiornithean.[86]

"Unnamed hesperornithiform A"[86]

Unnamed
  • Montana
  • UCMP 13355, a tarsometatarsus

A primitive hesperornithiform.[88] The Hell Creek specimen was referred to the same unnamed taxon as RSM P 2315.1 from the Canadian Frenchman Formation.[86] RSM P 2315.1 was later made the holotype of Brodavis americanus.[88] May be a synonym of Potamornis.[86]

"Unnamed ornithurine B"[86]

Unnamed[96]
  • UCMP 129143, a partial coracoid[86]

An ornithurine possibly similar to Cimolopteryx[86][96]

"Unnamed ornithurine C"[86]

Unnamed
  • SDSM 64281A, a partial coracoid[86]
  • SDSM 64281B, a partial coracoid[86]
  • UCMP 175251, a partial coracoid[86]
  • MOR 2918, a partial coracoid[86]

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[86]

"Unnamed ornithurine D"[86]

Unnamed
  • UCMP 187207, a partial coracoid[86]

An ichthyornithean also present in the Frenchman Formation[86]

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.[98][99] Indeterminate pteranodontid remains have also been found here as well.[100][101]

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

Azhdarchidae spp.

Indeterminate
  • Montana[98]
  • 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.[98]

Pterosaur spp.[102]

Indeterminate
  • South Dakota

Crocodylomorphs

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[103]
  • Montana
  • North Dakota
  • South Dakota

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

Brachychampsa[103]
  • Montana
  • South Dakota
  • North Dakota

Extinct genus of alligatoroid.

Thoracosaurus[103]
  • Montana

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

Turtles

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[104]

Indeterminate[104]

Extinct genus of aquatic turtles belonging to the family Adocidae.

Axestemys[106]

A. infernalis[106]
  • 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.[107][106]

Compsemys[104]

C. victa[104]

A relative of Dermatemydidae.

Peckemys

P. brinkman
  • Montana
  • North Dakota

A relative of Baenidae.

Emarginachelys

E. cretacea
  • Montana

A relative of chelydrids.[108]

Eubaena[104]

E. cephalica[104]

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[108]

H. clark[108]

A kinosternoid related to the Central American river turtle.[108]
Hutchemys[109] H. walkerorum[109] A shell[109] A Plastomeninae related to the softshell turtle.[109]

Plastomenus

P. sp

Trionychidae turtle.

Basilemys

B. sinuosa

Largest dermatemydid land tortoise.

Trionyx[104]

Indeterminate[104]

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[110]

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.[111][112]

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[113][114]

C. monstrosus[113][114]

A platynotan lizard of uncertain phylogenetic placement, also known from the Lance Formation.[113]

Cerberophis[113][114]

C. robustus[113][114]

An alethinophidian snake of uncertain phylogenetic placement.[113]

Obamadon[113][114]

O. gracilis[113][114]

A polyglyphanodontian lizard of uncertain phylogenetic placement. Also known from the Lance Formation.[113]

Peneteius[113]

P. aquilonius[113]

A chamopsiid polyglyphanodontian lizard.[113]

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

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[103]

C. laramiensis[103]
  • Montana

A champsosaur.


Mammals

Multituberculates

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[115]

C. minor[115]

A multituberculate of uncertain phylogenetic placement.

Cimolodon[115]

C. nitidus
  • Montana
  • North Dakota[115]

A cimolodontid multituberculate.

C. cf. nitidus[115]

A cimolodontid multituberculate.

C. sp.[115]

A cimolodontid multituberculate.

Cimolomys[115]

C. gracilis

A cimolomyid multituberculate.

A cimolomyid multituberculate.

Essonodon[115]

E. browni[115]

A cimolomyid multituberculate.

Meniscoessus[115]

M. conquistus

A cimolomyid multituberculate.

M. robustus
  • Montana
  • North Dakota
  • South Dakota[115]

A cimolomyid multituberculate.

M. cf. robustus

A cimolomyid multituberculate.

M. sp.

A cimolomyid multituberculate.

?M. sp.[115]

A cimolomyid multituberculate.

Mesodma[115]

M. formosa
  • Montana
  • South Dakota[115]

A neoplagiaulacid multituberculate.

M. cf. formosa

A neoplagiaulacid multituberculate.

M. hensleighi
  • Montana
  • South Dakota[115]

A neoplagiaulacid multituberculate.

M. cf. hensleighi

A neoplagiaulacid multituberculate.

M. thompsoni
  • Montana
  • North Dakota
  • South Dakota[115]

A neoplagiaulacid multituberculate.

M. cf. thompsoni

A neoplagiaulacid multituberculate.

M sp.[115]

A neoplagiaulacid multituberculate.

?M sp.[115]

A neoplagiaulacid multituberculate.

?Neoplagiaulax[115]

?N. burgessi[115]

A neoplagiaulacid multituberculate.

Paracimexomys[115]

P. priscus[115]

A multituberculate of uncertain phylogenetic placement.

Paressonodon[116]

P. nelsoni[116]

A cimolomyid multituberculate.

Stygimys

S. kuszmauli
  • Montana

It was a member of the extinct order Multituberculata.

Metatherians

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

Aletridelphys[117][118]

A. florencae
  • Montana
  • North Dakota
  • South Dakota[115]

A pediomyid.

A. hatcheri[117]
  • Montana
  • South Dakota[115]

A pediomyid.

Alphadon[115]

A. marshi
  • Montana
  • North Dakota[115]

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[115]

An alphadontid.

A. wilsoni

An alphadontid.

A. cf. wilsoni

An alphadontid.

A. sp.[115]
  • North Dakota
  • South Dakota[115]

An alphadontid.

Didelphodon[115]

D. padanicus

A stagodontid.

D. vorax
  • Montana
  • North Dakota[115]

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


D. cf. vorax

A stagodontid.

D. sp.

A stagodontid.

cf. D. sp.[115]
  • North Dakota
  • South Dakota[115]

A stagodontid.

Glasbius[115]

G. twitchelli

A glasbiid.

G. cf. twitchelli[115]

A glasbiid.

Leptalestes[117]

L. cooki

A pediomyid.

L. krejcii[117]
  • Montana
  • South Dakota[115]

A pediomyid.

Nanocuris[116]

N. improvida[116]

A deltatheridiid.

Nortedelphys

N. jasoni (= N. intermedius)[116][119]
  • Montana
  • South Dakota

A herpetotheriid.

Pediomys[115]

P. elegans[115]
  • Montana
  • South Dakota[115]

A pediomyid.

Protalphadon[115]

P. foxi

An alphadontid.

P. lulli[115]

An alphadontid.

Turgidodon[115]

T. rhaister[115]

An alphadontid.

Eutherians

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[120]

Alostera[115]

A. saskatchewanensis[115]

A eutherian of uncertain phylogenetic placement.

Ambilestes

A. cerberoides
  • Montana

A eutherian of uncertain classification, formally a species of Cimolestes

Batodon[115]

B. tenuis[115]

A cimolestid eutherian.

Cimolestes[115]

C. incisus

A cimolestid eutherian.

C. stirtoni[115]

A cimolestid eutherian.

Gypsonictops[115]

G. hypoconus
  • Montana
  • South Dakota[115]

A gypsonictopsid eutherian.

G. illuminatus
  • Montana
  • North Dakota[115]

A gypsonictopsid eutherian.

G. cf. illuminatus

A gypsonictopsid eutherian.

G. sp.[115]

A gypsonictopsid eutherian.

cf. Paranyctoides[115]

cf. Paranyctoides sp.[115]

A nyctitheriid eutherian.

Protungulatum[117]

P. coombsi[117]

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.[121][122] 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)
Plants of the Hell Creek Formation

Gymnosperms

Ginkgos

Angiosperms

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
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[123][124]

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

References

  1. ↑ 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. ↑ 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. 1 2 3 4 5 Graf, Dan; Cummings, Kevin. "The Mussel Project". UWSP Mussel Project. The University of Wisconsin-Stevens Point. Retrieved 7 June 2021.
  7. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 Pearson et al. (2002) p. 154
  8. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Pearson et al. (2002) pp. 145–167
  9. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Pearson et al. (2002) p. 155
  10. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Pearson et al. (2002) pp. 156
  11. ↑ Listed as "cf. Barbourula sp." in "Class Amphibia," Estes and Berberian, (1970). Page 4.
  12. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 "Class Amphibia," in Estes and Berberian, (1970). Page 4.
  13. 1 2 3 4 5 6 7 8 9 "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. 1 2 3 4 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.
  16. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 "Class Osteichthyes," in Estes and Berberian, (1970). Page 3.
  17. 1 2 3 4 5 6 7 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. ISSN 0022-3360. S2CID 252702937.
  18. 1 2 3 4 5 6 7 8 "Class Osteichthyes," in Estes and Berberian, (1970). Page 3. All taxa listed occur in Montana, see page 1.
  19. 1 2 3 4 Sato, Hiroki; Murray, Alison M.; Vernygora, Oksana; Currie, Philip J. (2018-07-04). "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. ISSN 0272-4634. S2CID 92574712.
  20. 1 2 3 4 "Class Osteichthyes," in Estes and Berberian, (1970). Page 4.
  21. 1 2 3 "Class Osteichthyes," in Estes and Berberian, (1970). Page 4. All taxa listed occur in Montana, see page 1.
  22. ↑ Grande, Lance; Bemis, William E. (1998-04-10). "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. ISSN 0272-4634.
  23. ↑ 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. ISSN 0045-8511.
  24. 1 2 Listed as "cf. Paralbula casei" in "Class Osteichthyes," Estes and Berberian, (1970). Page 4.
  25. 1 2 3 4 5 6 Hilton, Eric J.; During, Melanie A. D.; Grande, Lance; Ahlberg, Per E. (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. ISSN 0022-3360. S2CID 258095684.
  26. 1 2 3 Grande, Lance; Bemis, William E. (1991). "Osteology and Phylogenetic Relationships of Fossil and Recent Paddlefishes (Polyodontidae) with Comments on the Interrelationships of Acipenseriformes". Memoir (Society of Vertebrate Paleontology). 1: ii–121. doi:10.2307/3889328. ISSN 1062-161X. JSTOR 3889328.
  27. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 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.
  28. 1 2 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.
  29. 1 2 "Class Chondrichthyes," in Estes and Berberian, (1970). Page 3.
  30. ↑ "Class Chondrichthyes," in Estes and Berberian, (1970). Page 3. All taxa listed occur in Montana, see page 1.
  31. ↑ 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.
  32. ↑ 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.
  33. 1 2 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.
  34. 1 2 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.
  35. ↑ Carpenter, K. (1 November 2002). "Late Cretaceous dinosaurs from the Denver Basin, Colorado" (PDF). Rocky Mountain Geology. 37 (2): 237–254. Bibcode:2002RMGeo..37..237C. doi:10.2113/11.
  36. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 "Dinosaur distribution (Late Cretaceous; North America; Montana)." Weishampel, et al. (2004). Page 584.
  37. 1 2 3 4 5 6 7 8 9 10 11 "Dinosaur distribution (Late Cretaceous; North America; South Dakota)." Weishampel, et al. (2004). Page 586.
  38. 1 2 3 4 "Dinosaur distribution (Late Cretaceous; North America; North Dakota)." Weishampel, et al. (2004). Page 585.
  39. ↑ 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. JSTOR 4523163.
  40. 1 2 3 4 Bakker et al. (2006)
  41. 1 2 3 4 5 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. S2CID 258154892.
  42. ↑ 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.
  43. 1 2 3 4 5 6 Woodruff, D. Cary; Schott, Ryan K.; Evans, David C. (2023-11-15). "Two new species of small‐bodied pachycephalosaurine (Dinosauria, Marginocephalia) from the uppermost Cretaceous of North America suggest hidden diversity in well‐sampled formations". Papers in Palaeontology. 9 (6). e1535. doi:10.1002/spp2.1535. ISSN 2056-2799.
  44. ↑ "Table 21.1," in Weishampel, et al. (2004). Page 465.
  45. ↑ Carpenter, Kenneth (2006). Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Bloomington, IN: Indiana University Press. ISBN 978-0253348173. Retrieved 13 November 2020.
  46. ↑ 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. JSTOR j.ctt16gzgng.
  47. ↑ 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).
  48. ↑ Scannella, B.; Fowler, W.; Goodwin, B.; Horner, R. (2014). "Evolutionary Trends in Triceratops from the Hell Creek Formation, Montana (Project)". doi:10.7934/p1099. {{cite journal}}: Cite journal requires |journal= (help)
  49. ↑ 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. S2CID 228888356.
  50. ↑ Biles, Jan. "Rare dinosaur skull being prepared for exhibition". Topeka Capital-Journal.com. Topeka Capital-Journal. Retrieved 7 September 2015.
  51. ↑ "Super-sized Ceratopsian Skull Might be New Species". Everything Dinosaur. 29 August 2015. Retrieved 29 August 2015.
  52. ↑ O' Connell, Max (27 August 2015). "Dinosaur skull found in Buffalo likely a new species". Rapid City Journal. Retrieved 27 August 2015.
  53. ↑ Ostrom, John H. (May 1978). "Leptoceratops gracilis from the 'Lance' Formation of Wyoming". Journal of Paleontology. 52 (3): 697–704. JSTOR 1303974.
  54. 1 2 3 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.
  55. ↑ Nicholas R. Longrich (2011). "Titanoceratops ouranous, a giant horned dinosaur from the Late Campanian of New Mexico". Cretaceous Research. 32 (3): 264–276. Bibcode:2011CrRes..32..264L. doi:10.1016/j.cretres.2010.12.007.
  56. ↑ 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. Bibcode:2010JVPal..30.1157S. doi:10.1080/02724634.2010.483632. S2CID 86767957.
  57. ↑ 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.
  58. ↑ 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. S2CID 133184183.
  59. 1 2 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. Bibcode:2014PNAS..11110245S. doi:10.1073/pnas.1313334111. ISSN 0027-8424. PMC 4104892. PMID 24982159.
  60. 1 2 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. Bibcode:2011PLoSO...625186C. doi:10.1371/journal.pone.0025186. PMC 3182183. PMID 21969872.
  61. ↑ Manning, Phillip L.; Morris, Peter M.; McMahon, Adam; Jones, Emrys; Gize, Andy; Macquaker, Joe H. S.; Wolff, George; Thompson, Anu; Marshall, Jim; Taylor, Kevin G.; Lyson, Tyler; Gaskell, Simon; Reamtong, Onrapak; Sellers, William I.; van Dongen, Bart E.; Buckley, Mike; Wogelius, Roy A. (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. JSTOR 30244137. PMC 2817188. PMID 19570788.
  62. ↑ 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. Bibcode:2013CrRes..46..114V. doi:10.1016/j.cretres.2013.08.010.
  63. ↑ Rohrer, W. L.; Konizeski, R. (May 1960). "On the Occurrence of Edmontosaurus in the Hell Creek Formation of Montana". 34. 34 (3): 464–466. JSTOR 1300943.
  64. 1 2 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. Bibcode:2017JVPal..37E8168W. doi:10.1080/02724634.2017.1398168. S2CID 90735967.
  65. 1 2 Listed as "?Thescelosaurus garbanii" in "Dinosaur distribution (Late Cretaceous; North America; Montana)." Weishampel, et al. (2004). Page 584.
  66. 1 2 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.
  67. ↑ Noted as being present, although misspelled as "Thescelosaurus garbani, in " "Dinosaur distribution (Late Cretaceous; North America; South Dakota)." Weishampel, et al. (2004). Page 586.
  68. ↑ Boyd, Brown, et al. (2009)
  69. ↑ 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. JSTOR 1303302.
  70. ↑ 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. Bibcode:2008Palai..23..645M. doi:10.2110/palo.2008.p08-030r. JSTOR 27670550. S2CID 129985735.
  71. ↑ 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.
  72. ↑ Molnar, R.E. (January 1980). "An Albertosaur from the Hell Creek Formation of Montana". Journal of Paleontology. 54 (1): 102–108. JSTOR 1304167.
  73. ↑ 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.
  74. ↑ Hutchinson and Chiappe, 1998. The first known alvarezsaurid (Theropoda: Aves) from North America. Journal of Vertebrate Paleontology. 18(3), 447–450.
  75. ↑ 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". PLOS ONE. 6 (2): e16574. Bibcode:2011PLoSO...616574H. doi:10.1371/journal.pone.0016574. ISSN 1932-6203. PMC 3036655. PMID 21347420.
  76. ↑ 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
  77. 1 2 3 Longrich (2008), pages 983–996.
  78. 1 2 3 4 5 6 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. Bibcode:2014PLoSO...992022L. doi:10.1371/journal.pone.0092022. PMC 3960162. PMID 24647078.
  79. ↑ Stein, Walter W. (2019). "TAKING COUNT: A Census of Dinosaur Fossils Recovered From the Hell Creek and Lance Formations (Maastrichtian)" (PDF). The Journal of Paleontological Sciences. 8: 1–42.
  80. ↑ 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 (Report). in "Abstracts of Papers". Journal of Vertebrate Paleontology. 26: 1–152. 2006. Bibcode:2006JVPal..26S...1.. doi:10.1080/02724634.2006.10010069.
  81. ↑ 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. Retrieved 18 October 2020.
  82. ↑ 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)" (PDF). Canadian Society of Vertebrate Paleontology: 17–18. Retrieved 17 November 2020.
  83. 1 2 3 4 5 6 7 8 9 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. Bibcode:2013NW....100.1041E. doi:10.1007/s00114-013-1107-5. PMID 24248432. S2CID 14978813.
  84. ↑ 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. Retrieved 23 October 2020.
  85. ↑ Dinosaur distribution (Late Cretaceous; North America; North Dakota). Weishampel, et al. (2004). Page 585
  86. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 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. Bibcode:2011PNAS..10815253L. doi:10.1073/pnas.1110395108. PMC 3174646. PMID 21914849.
  87. 1 2 3 Stidham, 1999. North American avisaurids (Aves: Enantiornithes): New data on morphology and phylogeny. VII International Symposium on Mesozoic Terrestrial Ecosystems, abstracts.
  88. 1 2 3 4 5 6 7 8 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.
  89. 1 2 3 4 5 6 7 8 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.
  90. 1 2 3 4 Olshevsky, G., 1991, A Revision of the Parainfraclass Archosauria Cope, 1869, Excluding the Advanced Crocodylia. Mesozoic Meanderings 2 pp 196
  91. 1 2 Carpenter, K. (1982). "Baby dinosaurs from the Late Cretaceous Lance and Hell Creek formations and a description of a new species of theropod" (PDF). Contributions to Geology, University of Wyoming. 20 (2): 123–134.
  92. 1 2 3 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:aaqftl]2.0.co;2. S2CID 86292770.
  93. 1 2 Estes, Richard (1964). Fossil vertebrates from the late Cretaceous Lance formation, eastern Wyoming. University of California Press. OCLC 3753287.
  94. 1 2 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. Bibcode:2013PLoSO...854329L. doi:10.1371/journal.pone.0054329. PMC 3553132. PMID 23372708.
  95. ↑ 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.
  96. 1 2 "Class Aves," in Estes and Berberian, (1970). Page 7.
  97. ↑ "Class Aves," in Estes and Berberian, (1970). Page 7. All taxa listed occur in Montana, see page 1.
  98. 1 2 3 Henderson, Michael; Peterson, Joseph (30 March 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.
  99. ↑ Averianov, Alexander (11 August 2014). "Review of taxonomy, geographic distribution, and paleoenvironments of Azhdarchidae (Pterosauria)". ZooKeys (432): 1–107. Bibcode:2014ZooK..432....1A. doi:10.3897/zookeys.432.7913. PMC 4141157. PMID 25152671.
  100. ↑ 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. PMC 5849296. PMID 29534059.
  101. ↑ 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. PMC 5894959. PMID 29641516.
  102. ↑ "New Hell Creek Pterosaur Species". TrieboldPaleo.Inc.
  103. 1 2 3 4 5 6 7 8 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.
  104. 1 2 3 4 5 6 7 8 "Order Testudinata," in Estes and Berberian, (1970). Page 5.
  105. 1 2 3 4 "Order Testudinata," in Estes and Berberian, (1970). Page 5. All taxa listed occur in Montana, see page 1.
  106. 1 2 3 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.
  107. ↑ 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. PMC 4756751. PMID 26893972.
  108. 1 2 3 4 5 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. S2CID 129123961.
  109. 1 2 3 4 5 "Cretaceous-Period Softshell Turtle Lived alongside Giant Dinosaurs | Sci-News.com". Breaking Science News | Sci-News.com. 14 March 2022. Retrieved 2022-03-15.
  110. ↑ 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. Bibcode:2019JVPal..39E2428L. doi:10.1080/02724634.2019.1662428. S2CID 208587902.
  111. ↑ "Fossils may capture the day the dinosaurs died. Here's what you should know". Science. 2019-03-31. Archived from the original on March 5, 2021. Retrieved 2021-08-20.
  112. ↑ 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" (PDF). PaleoBios. 38. doi:10.5070/P938054460. ISSN 0031-0298. S2CID 238659131.
  113. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 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. Bibcode:2012PNAS..10921396L. doi:10.1073/pnas.1211526110. PMC 3535637. PMID 23236177.
  114. 1 2 3 4 5 6 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. Bibcode:2013PNAS..110Q6608.. doi:10.1073/pnas.1303907110. PMC 3631639.
  115. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 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
  116. 1 2 3 4 5 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. Bibcode:2013Pbio...39..429W. doi:10.1666/12041. S2CID 36025237.
  117. 1 2 3 4 5 6 7 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. S2CID 16724836.
  118. ↑ Davis, B. M. (2007). "A revision of 'pediomyid' marsupials from the Late Cretaceous of North America". Acta Palaeontologica Polonica. 2 (52).
  119. ↑ 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. Bibcode:2012JSPal..10..625W. doi:10.1080/14772019.2011.631592. S2CID 83996185.
  120. ↑ 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. Bibcode:2015CaJES..52.1137F. doi:10.1139/cjes-2015-0113.
  121. ↑ Chandrasekharam, A., 1974. Megafossil flora from the Genesee locality, Alberta, Canada. Palaeontographica, Abt. A, Band 174
  122. ↑ Christophel, D.C., 1976. Fossil floras from the Smoky Tower locality, Alberta, Canada. Palaeontographica, Abt. B, Band 157
  123. ↑ 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.
  124. ↑ 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

General
Geology
Paleontology
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.