Hell Creek fauna

Tyrannosaurus () is a genus of large theropod dinosaur. The type species Tyrannosaurus rex ( meaning 'king' in Latin), often shortened to T. rex or colloquially t-rex, is one of the best represented theropods. It lived throughout what is now western North America, on what was then an island continent known as Laramidia. Tyrannosaurus had a much wider range than other tyrannosaurids. Fossils are found in a variety of geological formations dating to the late Maastrichtian age of the late Cretaceous period, 69 to 66 million years ago, with isolated specimens possibly indicating an earlier or

Triceratops ( ; ) is a genus of chasmosaurine ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous period, about 68 to 66 million years ago on the island continent of Laramidia, now forming western North America. It was one of the last-known non-avian dinosaurs and lived until the Cretaceous–Paleogene extinction event 66 million years ago. The name Triceratops, which means 'three-horned face', is derived from the Ancient Greek words ('), meaning "three", ('), meaning "horn", and (''''), meaning "face".

Ankylosaurus is a genus of armored dinosaur. Its fossils have been found in geological formations dating to the very end of the Cretaceous Period, about 70-66 million years ago, in western North America, making it among the last of the non-avian dinosaurs. It was named by Barnum Brown in 1908; it is monotypic, containing only A. magniventris. The generic name means "fused" or "bent lizard", and the specific name means "great belly". A handful of specimens have been excavated to date, but a complete skeleton has not been discovered. Though other members of Ankylosauria are represented by more e

Pachycephalosaurus (; meaning "thick-headed lizard", from Greek pachys/ "thickness", kephalon/ "head" and sauros/ "lizard") is a genus of pachycephalosaurid ornithischian dinosaur. The type species, P. wyomingensis, is the only known definitive species. The possibly synonymous taxon, Stygimoloch, might represent a distinct genus or a second species, P. spinifer. It lived during the Maastrichtian age of the Late Cretaceous period in what is now western North America. Remains have been excavated in Montana, South Dakota, Wyoming, and Alberta. Mainly known from a single skull and a few

Edmontosaurus ( ) (meaning "lizard from Edmonton"), often colloquially and historically known as Anatosaurus or Anatotitan (meaning "duck lizard" and "giant duck"), is a genus of hadrosaurid (duck-billed) dinosaur. It contains two known species: Edmontosaurus regalis and Edmontosaurus annectens. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian age of the Cretaceous period 73 million years ago, while those of E. annectens were found in the same geographic region from rocks dated to the end of the Maastrichtian age, 66 million years a

Torosaurus (meaning "perforated lizard", in reference to the large openings in its frill) is a genus of herbivorous chasmosaurine ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous period, between 68 and 66 million years ago, though it is possible that the species range might extend to as far back as 69 million years ago. Fossils have been discovered across the Western Interior of North America, from as far north as Saskatchewan to as far south as Texas.

Leptoceratops (meaning 'small horn face') is a genus of ceratopsian dinosaur from the Late Cretaceous of North America. First found in Alberta in 1910, the type species Leptoceratops gracilis was named in 1914 by Barnum Brown for a partial skull and skeleton of two individuals found in the Scollard Formation of Alberta. Additional specimens found in the Scollard include one complete and two mostly complete skeletons together, uncovered in 1947 by Charles M. Sternberg. Specimens from Montana that were among the earliest referred to Leptoceratops have since been moved to their own genera Montano

Thescelosaurus ( ) is a genus of ornithischian dinosaur that lived during the Late Cretaceous period in western North America. It was named and described in 1913 by the paleontologist Charles W. Gilmore; the type species is T. neglectus. Two other species, T. garbanii and T. assiniboiensis, were named in 1976 and 2011, respectively. Additional species have been suggested but are currently not accepted. Thescelosaurus is the eponymous member of its family, the Thescelosauridae. Thescelosaurids are either considered to be basal ("primitive") ornithopods, or are placed outside of this group withi

Nanotyrannus (/ˈnænoʊˌtaɪˌrænəs, -tɪ- /, ) is a genus of tyrannosauroid dinosaur that lived in what is now western North America during the Maastrichtian age of the Late Cretaceous, . Its fossils are known from the Hell Creek Formation. It was one of the last-known non-avian dinosaurs and lived until the Cretaceous–Paleogene extinction event. The first named species, N. lancensis, was described as a new species of Gorgosaurus in 1946 by Charles W. Gilmore based on a single skull. Re-examination of the specimen in 1988 by Robert T. Bakker, Michael Williams and Philip J. Currie moved the species

Purgatorius is an extinct genus of eutherian mammal from the early Paleocene epoch of western North America. It is typically believed to be the earliest example of a primate or protoprimate (a primatomorph precursor to the Plesiadapiformes), dating to nearly as old as 66 million years ago.

Dakotaraptor (meaning "thief from Dakota") is a possible chimaeric genus of maniraptoriform theropod dinosaur that lived in western North America during the Late Cretaceous period. The remains have been found in the Maastrichtian-aged Hell Creek Formation, dated to the very end of the Mesozoic era, making Dakotaraptor potentially one of the last surviving dromaeosaurids, though other researchers have disputed its classification. One of the largest dromaeosaurids, measuring and weighing , the remains of D. steini were discovered in a multi-species bonebed. Elements of the holotype and referred

Sphaerotholus is a genus of pachycephalosaurid dinosaur from the Upper Cretaceous of the western United States and Canada. To date, five species have been described: the type species, S. goodwini, from the Den-na-zin Member of the Kirtland Formation and possibly the Fossil Forest Member of the Fruitland Formation (Late Campanian) of San Juan County, New Mexico, USA; S. buchholtzae, from the Hell Creek Formation (Late Maastrichtian) of western Carter County, Montana, USA and the Frenchman Formation of Saskatchewan, Canada; S. edmontonensis, from the Horseshoe Canyon Formation of Alberta, Canada

Champsosaurus is an extinct genus of crocodile-like choristodere reptile, known from the Late Cretaceous and early Paleogene periods of North America and Europe (Campanian–Paleocene). The name Champsosaurus is thought to come from , () said in an Ancient Greek source to be an Egyptian word for "crocodiles", and , () Greek for "lizard". The morphology of Champsosaurus resembles that of gharials, with a long, elongated snout. It was native to freshwater environments where it likely preyed on fish, similar to living gharials.

Tatankaceratops (meaning "bison horned face") is a controversial genus of herbivorous chasmosaurine ceratopsid dinosaur that lived during the Late Cretaceous period (latest Maastrichtian stage, about 66 million years ago) in what is now the upper Hell Creek Formation, in South Dakota. It is known from a single partial skull housed at the Black Hills Institute, BHI 6226, described by Christopher J. Ott and Peter L. Larson in 2010 as the type species Tatankaceratops sacrisonorum.

Avisaurus (meaning "bird lizard") is a genus of enantiornithine avialan from the Late Cretaceous of North America.

Didelphodon (from [[Didelphis|[is]]] "opossum" and "tooth") is a genus of extinct metatherian mammal from the Late Cretaceous of North America.

Paronychodon (meaning "beside claw tooth") is an extinct theropod dinosaur genus. It is a tooth taxon, often considered dubious because of the fragmentary nature of the fossils, which include "buckets" of teeth from many disparate times and places but no other remains, and should be considered a form taxon.

Alphadon is an extinct genus of small, primitive mammal that was a member of the metatherians, a group of mammals that includes modern-day marsupials. Its fossils were first discovered and named by George Gaylord Simpson in 1929.

Acheroraptor is an extinct genus of dromaeosaurid theropod dinosaur known from the latest Maastrichtian Hell Creek Formation of Montana, United States. It contains a single species, Acheroraptor temertyorum. A. temertyorum is one of the two geologically youngest known species of dromaeosaurids, the other being the possibly dubious Dakotaraptor steini, which is also known from the same formation. A basal cousin of Velociraptor, Acheroraptor is known from upper and lower jaw material.

Borealosuchus (meaning "northern crocodile") is an extinct genus of crocodyliforms that lived from the Late Cretaceous to the Eocene in North America. It was named by Christopher Brochu in 1997 for several species that had been assigned to Leidyosuchus. The species assigned to it are: B. sternbergii, the type species, from the Maastrichtian (Late Cretaceous) of Colorado, Montana, North Dakota, South Dakota, and Wyoming; B. acutidentatus, from the Paleocene of Saskatchewan; B. formidabilis, from the Paleocene of North Dakota; B. griffithi, from the Paleocene of Alberta; and B. wilsoni, from the

Pectinodon is a genus of troodontid theropod dinosaurs from the end of the Maastrichtian age of the Late Cretaceous period (66 mya). It currently contains a single valid species, Pectinodon bakkeri (sometimes classified as Troodon bakkeri), known only from teeth.

Cimolestes (from Ancient Greek , 'chalk robber') is a genus of early eutherians with a full complement of teeth adapted for eating insects and other small animals. Paleontologists have disagreed on its relationship to other mammals, in part because quite different animals were assigned to the genus, making Cimolestes a grade taxon of animals with similar features rather than a genus of closely related ones. Fossils have been found in North America, South America, Europe and Africa. Cimolestes first appeared during the Late Cretaceous of North America. According to some paleontologists, Cimoles

Thoracosaurus (chest lizard) is an extinct genus of long-snouted eusuchian which existed during the Late Cretaceous and Early Paleocene in North America and Europe.

Trionyx is a genus of softshell turtles belonging to the family Trionychidae. In the past many species in the family were classified in this genus, but today T. triunguis, the African or Nile softshell turtle, is the only extant softshell still classified as Trionyx. The other species still assigned to this genus are only known from fossils. T. triunguis is a relatively large, aquatic piscivore.

Protungulatum ('first ungulate') is an extinct genus of eutherian mammals within extinct family Protungulatidae, and is possibly one of the earliest known placental mammals in the fossil record, that lived in North America from the Late Cretaceous to early Paleocene.

Trierarchuncus (meaning "captain hook," after its single-clawed hands) is a monotypic genus of alvarezsaurid theropod which includes a single species, Trierarchuncus prairiensis, mainly known from fossils found in deposits of the Hell Creek Formation in Montana. It is the youngest known alvarezsaurid and one of the last non-avian dinosaurs, going extinct during the Cretaceous–Paleogene extinction event, which occurred approximately 66 million years ago.

Infernodrakon (meaning "dragon from hell") is a genus of azhdarchid pterosaurs from the Late Cretaceous Hell Creek Formation of Montana, United States. The genus contains a single species, I. hastacollis, known from a single neck vertebra. Based on comparisons with related azhdarchids, it probably had a wingspan of about .

Platytholus is an extinct genus of pachycephalosaurid dinosaur from the Late Cretaceous (Maastrichtian) Hell Creek Formation of the United States. The genus contains a single species, P. clemensi, known from a partial skull.

Brodavis is a genus of freshwater hesperornithiform birds known from the Late Cretaceous (possibly Campanian and Maastrichtian stage) of North America and Asia. It was first described and named by Larry D. Martin, Evgeny N. Kurochkin and Tim T. Tokaryk in 2012 and assigned to a new monogeneric family, Brodavidae. Four species were described and assigned to Brodavis.

Brachychampsa is an extinct genus of alligatorid, possibly a basal caiman. Specimens have been reported from New Mexico, Colorado, Wyoming, Montana, North and South Dakota, New Jersey, and Saskatchewan, though only those from Montana, Utah, and New Mexico are based on material sufficient to justify the referral. Some specimens have been reported from the Campanian-aged deposits of Central Asia (Chimkent of Kazakhstan and Kirkuduk of Tajikistan), although the species status is indeterminate for these fossils. The genus first appeared during the late Campanian stage of the Late Cretaceous (Judit

species of reptile (fossil)

Meniscoessus is a genus of extinct multituberculates from the Upper Cretaceous Period that lived in North America.

Potamornis is a prehistoric bird genus that dated back to the late Maastrichtian age of the late Cretaceous period. Its scrappy remains were found in the Lance Formation at Buck Creek, USA, and additional possible remains were found in the upper Hell Creek Formation of Montana, dated to the Danian age of the Paleogene period, though these may have been reworked. A single species was named and described in 2001: Potamornis skutchi.

Denversaurus (meaning "Denver lizard") is a genus of panoplosaurin nodosaurid dinosaur from the late Maastrichtian of Late Cretaceous Western North America. Although at one point treated as a junior synonym of Edmontonia by some taxonomists, current research indicates that it is its own distinct nodosaurid genus.

Mesodma is an extinct genus of mammal, a member of the extinct order Multituberculata within the suborder Cimolodonta, family Neoplagiaulacidae. It lived during the upper Cretaceous and Paleocene Periods of what is now North America. The earliest definitive record is from the late Santonian stage strata of the Straight Cliffs Formation. A single premolar tooth from the lower Cenomanian stage strata of the Cedar Mountain Formation has been tentatively assigned to this genus based on its similarity, but its describers noted that it is unlikely that Mesodma lived during that time.

Eoneophron (meaning "dawn Neophron") is an extinct genus of caenagnathid theropod dinosaur from the Late Cretaceous Hell Creek Formation of South Dakota, US. The genus contains a single species, E. infernalis, known from a partial hindlimb.

species of reptile (fossil)

Obamadon is an extinct genus of polyglyphanodontian lizards from the Late Cretaceous of North America. Fossils have been found in the Hell Creek Formation of Montana and the Lance Formation of Wyoming. Researchers describe it as being distinguished by its "tall, slender teeth with large central cusps separated from small accessory cusps by lingual grooves." The type species was named Obamadon gracilis after United States president Barack Obama, "in reference to the tall, straight teeth, and the manner in which Mr. Obama has acted as a role model of good oral hygiene for the world." According t

Palaeosaniwa is an extinct genus of carnivorous lizard from the Late Cretaceous of North America. The type (and only) species, Palaeosaniwa canadensis, given by Charles Whitney Gilmore in 1928, means "ancient Saniwa from Canada".

Axestemys is an extinct genus of softshell turtle that lived from the Late Cretaceous to the Eocene in western North America and Europe.

Adocus is an extinct genus of aquatic turtles belonging to the family Adocidae.

Cimolomys (Greek for "chalk mouse") is a mammal genus from the Upper Cretaceous of North America. It was a member of the extinct order Multituberculata within the suborder Cimolodonta and family Cimolomyidae.

Sphenodiscus is an extinct genus of acanthoceratacean ammonite. The genus has been found from many continents and is thought to have had a large global distribution during the Maastrichtian stage of the Late Cretaceous. It was one of the last ammonoids to have evolved before the entire subclass became extinct during the Paleocene, which was directly after the Cretaceous–Paleogene extinction event.

Altacreodus ("creodont from Alberta") is an extinct genus of eutherian mammals. Fossils have been found in North America where they first appeared during the Late Cretaceous, and they died out prior to the start of the Paleocene. It is possibly one of the earliest known placental mammals in the fossil record.

Myledaphus is an extinct genus of guitarfish. It currently contains four valid species found in North America (M. bipartitus, M. pustulosus), South America (M. araucanus), and Central Asia (M. tritus). It is confirmed to have lived during the Late Cretaceous, with possible occurrences in the Paleocene and early Eocene. While the genus is mostly known from teeth, two partial skeletons of M. bipartitus have been found in the Dinosaur Park Formation of Alberta.

Nanocuris is an extinct genus of Deltatheridiidae from the Cretaceous of Canada (Saskatchewan) and United States (Wyoming - Lance Formation and Hell Creek Formation). Initially, it was classified in a proper family, Nanocuridae, in the clade Eutheria, but a reanalysis of a new specimen revealed a delthatheroid affinity of the genus.

thumb | right | alt=Pediomys upper and lower molars. | Pediomys upper and lower molars. Pediomys is an extinct genus of pediomyid marsupial from the Late Cretaceous of North America.

Turgidodon is an extinct genus of alphadontid marsupial from the Late Cretaceous of western North America.

Basilemys ("king turtle" in Greek) is a large, terrestrial nanhsiungchelyid turtle from the Upper Cretaceous of North and Central America. Most fossils of Basilemys have been found in rocks dating to the Campanian and Maastrichtian subdivisions of the Late Cretaceous and is considered to be the largest terrestrial turtle of its time. In an analysis made by Sukhanov et al. on a nansiunghelyid turtle from the Upper Cretaceous of Mongolia, it was demonstrated that Asian nanhsiungchelyids gave rise to the North American nanhsiungchelyids.

Protoscaphirhynchus squamosus is an extinct sturgeon from the Late Cretaceous of North America. It is known from a single poorly preserved specimen found in the Maastrichtian aged Hell Creek Formation in Montana. Due to its poor preservational state, it has few diagnostic characters.

Habrosaurus, meaning "graceful lizard", is an extinct genus of prehistoric salamanders, and the oldest and largest known member of the family Sirenidae. Two species are known, H. prodilatus from the middle Campanian Dinosaur Park Formation of Alberta, and H. dilatus from the late Maastrichtian and Paleocene of western North America. It is relatively common in the Lance Formation of Wyoming, and less common in the Hell Creek Formation of Montana. left|thumb|Artists reconstruction of Habrosaurus dilatus swimming by a cypress tree