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

Invertebrates

Insects

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

Molluscs

Amphibians

Fish

Bony fish

Bony fishes
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Acipenser	A. amnisinferos	North Dakota (Tanis)			A sturgeon
	A. eruciferus	Montana
	A. praeparatorum	North Dakota (Tanis)
	A. cf. A. amnisinferos	North Dakota (Tanis)
	cf. A. sp.	North Dakota South Dakota	Lower to upper Hell Creek Formation	18 specimens are tentatively assigned to Acipenser sp.	Acipenser sp. is tentatively referred to the genus.
Anchiacipencer	A. acanthaspis	Montana			A sturgeon, originally considered as indeterminate material
Belonostomus	B. longirostris	Montana North Dakota South Dakota	Lower to upper Hell Creek Formation	28 specimens	A long-snouted slender fish classified as an aspidorhynchid.
Coriops	C. amnicolus	Montana
Cyclurus	C. fragosus	Montana North Dakota South Dakota			A small amiid fish (ubiquitous). Previously known as Amia fragosa or Kindleia fragosa. 2610 specimens have been assigned to Kindleia, making it an extremely common genus.
"Lepisosteus"	"L. occidentalis"	Montana North Dakota South Dakota	Lower to uppermost Hell Creek Formation	938 specimens are assigned to Lepidosteus	A lepidosteid that is very common in the Hell Creek Formation. Nomen dubium.
Melvius	M. thomasi	North Dakota South Dakota	Lower to upper Hell Creek Formation	6 specimens are assigned to Melvius	A large amiid fish.
Phyllodus	P. paulkatoi				Fish with columnar teeth
Palaeolabrus	P. montanensis	Montana
Paleopsephurus	P. wilsoni	Montana			A paddlefish
Paralbula	P. casei	Montana
Parapsephurus	P. willybemisi	North Dakota (Tanis)			A paddlefish
Platacodon	P. nanus	Montana			Small teleost fish
Protamia	Indeterminate	Montana
Pachyrhizodontoidei	Indeterminate				Fish
Polyodontidae	Indeterminate	Montana			Paddlefish
Protoscaphirhynchus	P. squamosus	Montana			A sturgeon
Pugiopsephurus	P. inundatus	North Dakota (Tanis)			A paddlefish

Cartilaginous fish

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.

• Ceratopsidae 61%
• Hadrosauridae 23%
• Ornithomimidae 5%
• Tyrannosauridae 4%
• Hypsilophodontidae 3%
• Dromaeosauridae 2%
• Pachycephalosauridae 1%
• Troodontidae 1% (represented only by teeth)

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. 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.

Ornithischians

Ankylosaurs

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

Ankylosauria reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes	Images
Ankylosaurus	A. magniventris	Montana	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	D. schlessmani	Montana South Dakota		Skull roof, pelvis and osteoderms.	A nodosaurid ankylosaur whose remains have been found in the Lance and Laramie Formation.

Pachycephalosaurs

An undescribed and unnamed pachycephalosaur is present in North Dakota. 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.

Ceratopsians

Indeterminate ceratopsid teeth and some identifiable bones from Triceratops can be extremely common. 8.31% of all vertebrate remains from the Hell Creek Formation are unassigned ceratopsids. 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.

Ornithopods and relatives

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

Theropods

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

Alvarezsaurs

Tyrannosaurids

Ornithomimosaurs

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

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. In 2016, an undescribed large-bodied caenagnathid was unearthed in Montana.

Oviraptorosaurs reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes	Images
Anzu	A. wyliei	North Dakota South Dakota	Lower to upper Hell Creek Formation	12 well-preserved specimens	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.
Caenagnathidae	Indeterminate	Montana			Similar to Citipes and Elmisaurus.
Eoneophron	E. infernalis	South Dakota		A partial right hindlimb	Closely related 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. 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 and Saurornitholestes have been unearthed at the Hell Creek Formation and the nearby Lance Formation.

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. Indeterminate pteranodontid remains have also been found here as well.

Pterosaurs of the Hell Creek Formation
Taxa	Species	State	Stratigraphic location	Material	Notes	Images
Azhdarchidae spp.	Indeterminate	Montana 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.
Pterosaur spp.	Indeterminate	South Dakota

Crocodylomorphs

Turtles

Squamata

Indeterminate mosasaur remains have been unearthed in North Dakota; they may belong to a mosasaur measuring 11 m (36 ft) in length.

Choristoderans

Mammals

Multituberculates

Metatherians

Eutherians

Flora

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

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

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

Johnson claims that there are no grasses, oaks, maples, beeches, figs, or willows in the Hell Creek Formation. There is no evidence of fern prairie either. However, there was an extremely high angiosperm diversity — common plane trees, "Dryophyllum" subfalcatum, Leepierceia preartocarpoides, and palm trees — along with extinct cycadeoid Nilssoniocladus, Ginkgo, araucariaceous, podocarpaceous, and cupressaceous conifers. This represents the mixed deciduous and evergreen broad-leaved forest as the Hell Creek landscape. The nature of these forests is uncertain because Johnson found that the majority of the angiosperm and conifer genera are now extinct. He also believes that, very roughly 80% of the terrestrial plant taxa died out in what is now Great Plains at the K-Pg boundary. On other hand, there is a great increase in the abundance of fossil fern spores in the two centimeters of rock that directly overlies the impact fallout layer (the famous K-Pg boundary layer). This increase in fern spore abundance is commonly referred as "the fern spike" (meaning that if the abundance of spores as a function of stratigraphic position were plotted out, the graph would show a spike just above the impact fallout layer).

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

Compared to the rich Hell Creek Formation fossil plant localities of the Dakotas, relatively few plant specimens have been collected from Montana. A few taxa were collected at Brownie Butte Montana by Shoemaker, but most plants were collected from North Dakota (Slope County) and from South Dakota. Among the localities, the Mud Buttes, located in Bowman County, North Dakota, is probably the richest megaflora assemblage known and the most diverse leaf quarry from the Hell Creek Formation. "TYPE" after the binomial means that it is represented by a type specimen found in the Yale-Peabody Museum collections. "YPM" is the prefix for the Yale-Peabody Museum specimen number; "DMNH" is for the Denver Museum of Nature & Science; "USNM" is for Smithsonian National Museum of Natural History; and so on. The majority of Hell Creek megafloral specimens are collected at the Denver Museum of Nature & Science.

Overview (from Johnson, 2002)

302 plant morphotypes based on leaf only, including:

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

Paleoflora

Liverworts

Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Marchantia	M. pealii				Only known liverwort in Hell Creek.

Ferns

Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Equisetum	E. sp				Rare in the Hell Creek Formation.
Polypodiaceae?	indeterminate
Salvinia	S. sp				Floating aquatic plant.

Cycadophytes

Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Nilssoniocladus	N. comtula				Unlike N. yukonensis, its leaves are pinnatisect pinnules. Common.
	N. yukonensis				The only Hell Creek Formation cycadophyte. A simple leaf. Common.

Ginkgoales

Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Ginkgo	G. adiantoides				The only ginkgoalean in the Hell Creek Formation; uncommon

Conifers

Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Araucaria?	indeterminate				Casts of Monkey-puzzle leaves.
Cupressinocladus	C. interruptus				Casts of cupressaceae foliage. Uncommon
Dammarites	D. sp				A conifer seed cone. It's likely to belong to Elatides longifolia.
Ditaxocladus	D. catenulata				A cupressaceous conifer closely related to Cupressinocladus. Common.
Elatocladus	Elatocladus sp,				A taxodioid leaf morphogenus
Elatides	E. longifolia				Araucaria-like or Cunninghamia-like conifer. Less common in the lower 2/3 but more common in the upper 1/3 of the Hell Creek Formation.
Glyptostrobus	G. europaeus				Uncommon conifer.
Metasequoia	M. occidentalis				M. occidentalis seed cones are known from the Hell Creek.
Platyspiroxylon	Platyspiroxylon sp.				A cupressaceaeous wood morphogenus
Podocarpoxylon	Podocarpoxylon sp.				A possibly podocarpaceous wood morphogenus
Sequoiaxylon	Sequoiaxylon sp.				A cupressaceaeous wood morphogenus
Taxodioxylon	Taxodioxylon sp.				A cupressaceaeous wood morphogenus
Taxodium	T. olrikii				Related to today's bald cypress.
Unidentified	Unidentified				Unspecified cheirolepidiacous fossils

Angiosperms

Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
"Artocarpus"	"A." lessigiana				Abundant at Brownie Butte, Montana.
Annona?	A?. robusta				Abundant at Brownie Butte, Montana.
Araliaephyllum	A. polevoi				A lobed leaf. Closely relating to Bisonia. Fairly common.
Averrhoites	cf. A. affinis				An uncommon taxon with compound leaves.
Bisonia	B. niemi				A broad leaf, probably in the Laurales. A common taxon. Type specimen was found in South Dakota.
Browniea	B. serrata				In the Nyssaceae, closely relating to extant Camptotheca. Less common.
Cannabaceae?	indeterminate				Incertae sedis. It's not likely in the Cannabaceae.
Carpites	C. ulmiformis				Though this fossil fruit is abundant in the Early Paleocene, it's also found in Hell Creek. It may belong to Apiaceae.
"Celastrus"	"C." taurenensis				Incertae sedis. It's common in the lowermost to the middle Hell Creek Formation, but less common in the upper 1/3 Hell Creek Formation.
"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. Its affinity is questionable.
Cissites	cf. C. acerifolia				This morphotype was first described from the Cenomanian Dakota Group.
	C. insignis				This form represents of the group of Cenomanian leaves from Dakota Formation.
	C. lobata				A lobed leaf with half-naked basal lateral veins. Common in the upper 1/3 of the Hell Creek Formation.
	C. puilasokensis				A palmately lobed leaf with 5 primary veins. Common in the upper 1/3 of the Hell Creek Formation.
Cobbania	C. corrugata				A prehistoric species of water lettuce, previously assigned to the genus Pistia.
	C. hickeyi				Another Cobbania species from pond sediments known as "Licking Leaves."
Cornophyllum	C. newberryi				The majority of leaves are entire-margined but some may develop a few teeth.
"Cypercites"	"C." sp				A reed-type plant.
Dryophyllum	D. subfalcatum				This taxon is extremely common in the Hell Creek Formation, but is rare in Paleocene sediments. It is believed to be in Sabiaceae, closely related to the living Meliosma.
	aff. "Dryophyllum" subfalcatum				see above.
	"D." tenneseensis				This taxon is similar to D. subfalcatum]] but with extremely high L/W ratio and craspedodromous venation.
Erlingdorfia	E. montana				Johnson, 1996. In the Platanaceae (related to today's Sycamore). A very common taxon.
"Ficus"	"F." planicostata				Despite the genus name, it's in Lauraceae.
Grewiopsis	G. saportana				Another generic Platanaceae.
Harmsia	H. hydrocotyloidea				Incertae sedis. May be related to lotus. An uncommon taxon.
Humulus?	aff. Humulus sp.				May be related to the extant genus Humulus.
Hydropteris	H. pinnata				Floating aquatic fern
Limnobiophyllum	L. scutatum				Floating aquatic monocot, closely related to Pistia.
Liriodendrites	L. bradacii				Johnson, 1996. In the Magnoliidae: a common taxon.
"Liriodendron"	"L." laramiense				Unlobed leaf. May be related to today's tulip tree (yellow poplar). An uncommon taxon.
Liriodendron	L. sp				Four-lobed leaf. May be related to today's tulip tree (yellow poplar). An uncommon taxon.
Leepierceia	L. preartocarpoides				Incertae sedis but possibly in Proteales. Johnson, 1996.
Laurophyllum	L. wardiana				Large leaves. Closely related to "Dryophyllum" subfalcatum.
"Magnolia"	M. pulchra				Occurs in southern the Wyoming flora, Leo Hickey claims it is found further north in Montana and the Dakotas.
Marmarthia	M. johnsonii				A new Marmarthia species described in Peppe et al. 2007.
	M. pearsonii				Johnson, 1996. In the Lauraceae: a very common taxon.
	M. trivialis				Johnson, 1996. In the Lauraceae: a very common taxon.
"Myrica"	"Myrica" torreyi				Incertae sedis. Not actually a bayberry.
Nelumbo	N. sp				One of the most common aquatic plants in Hell Creek.
Nelumbium	N. montanum				An aquatic angiosperm, closely related to lotus. Uncommon.
Nordenskioldia	N. borealis				A fossil fruit likely to belonging to Zizyphoides flabella.
Paranymphaea	P. hastata				Despite the name, it's not related to extant genus Nymphaea.
Palaeoaster	P. porosia				A papaveraceous with fruits and seeds visually similar to Romneya though it's dubious.
Penosphyllum	P. cordatum				May be related to Sterculioideae. A common taxon.
Platanites	P. marginata				Johnson, 1996. In the Platanaceae. A common taxon.
	P. raynoldsii				An uncommon taxon.
Porosia	P. verrucosa				A fossil fruit that may belong to Rutaceae.
Rhamnica	R. cleburnii				Incertae sedis. A Tetracera look-alike leaf.
Sabalites	S. sp				Coryphoid palm tree. Very common.
Spinifructus	S. antiquus				A fruit seed that may belong to the palm family (Arecaceae), closely related to the genus Astrocaryum.
Trapago	T. angulata				A water caltrop look-alike.
Trochodendroides	T. arctica				A fossil fruit that may belong to Trochodendroides nebrascensis.
	T. ellipticum				A katsura look-alike. An uncommon taxon.
	T. genetrix				A katsura look-alike. A common taxon.
	T. nebrascensis				A very common taxon.
"Vitis"	"V." stantonii				Possibly a member of the Platanaceae rather than Vitaceae
"Ziziphus"	"Z." fibrillosus				A common taxon.
Zingiberopsis	Z. attenuata				Related to today's ginger plant. Its closest living relative is the Asian genus Alpinia. Some Hell Creek Formation specimens show damage from hispine beetles ("leaf beetles" (Wilf et al., 2000)).
	Z. magnifolia				Another Zinigberopsis species, previously assigned to Canna? magnifolia.
Zizyphoides	Z. flabella				An uncommon taxon.

Palynology

See also

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

References

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. Nel, André. "Maastrichtian representatives of the dragonfly family Aeschnidiidae question the entomofaunal turnover of the early Late Cretaceous". Palaeoentomology. Retrieved 17 Feb 2024.
7. ^ Graf, Dan; Cummings, Kevin. "The Mussel Project". UWSP Mussel Project. The University of Wisconsin-Stevens Point. Retrieved 7 June 2021.
8. ^ Pearson et al. (2002) p. 154
9. ^ Pearson et al. (2002) pp. 145–167
10. ^ Pearson et al. (2002) p. 155
11. ^ Pearson et al. (2002) pp. 156
12. Listed as "cf. Barbourula sp." in "Class Amphibia," Estes and Berberian, (1970). Page 4.
13. ^ "Class Amphibia," in Estes and Berberian, (1970). Page 4.
14. ^ "Class Amphibia," in Estes and Berberian, (1970). Page 4. All taxa listed occur in Montana, see page 1.
15. Listed as "Eopelobates? sp." in "Class Amphibia," Estes and Berberian, (1970). Page 4.
16. ^ David G. Demar Jr. (2013). "A new fossil salamander (Caudata, Proteidae) from the Upper Cretaceous (Maastrichtian) Hell Creek Formation, Montana, U.S.A". Journal of Vertebrate Paleontology. 33 (3): 588–598. Bibcode:2013JVPal..33..588D. doi:10.1080/02724634.2013.734887. S2CID 128532897.
17. ^ "Class Osteichthyes," in Estes and Berberian, (1970). Page 3.
18. ^ Hilton, Eric J.; Grande, Lance (2022-10-03). "Late Cretaceous sturgeons (Acipenseridae) from North America, with two new species from the Tanis site in the Hell Creek Formation of North Dakota". Journal of Paleontology. 97 (1): 189–217. doi:10.1017/jpa.2022.81. S2CID 252702937.
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