''Acheroraptor'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

dromaeosaurid Dromaeosauridae () is a family (biology), family of feathered coelurosaurian Theropoda, theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous period (geology), Period. The name Drom ...

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

known from the latest

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

Hell Creek Formation The Hell Creek Formation is an intensively studied division of mostly Upper Cretaceous and some lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana. The Formation (stratigraphy), formation s ...

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

, 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 '' Dakotaraptor steini'', which is also known from Hell Creek. A basal cousin of ''

Velociraptor ''Velociraptor'' (; ) is a genus of small dromaeosaurid dinosaurs that lived in Asia during the Late Cretaceous epoch, about 75 million to 71 million years ago. Two species are currently recognized, although others have been assigned in th ...

'', ''Acheroraptor'' is known from upper and lower jaw material.

Discovery and naming

''Acheroraptor'' was first described and named by David C. Evans, Derek W. Larson and Philip J. Currie in

2013 2013 was the first year since 1987 to contain four unique digits (a span of 26 years). 2013 was designated as: *International Year of Water Cooperation *International Year of Quinoa Events January * January 5 – 2013 Craig, Alask ...

and the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''Acheroraptor temertyorum''. The generic name is derived from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

Ἀχέρων, ''Acheron'', "underworld", in reference to the provenance from the

, and the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''raptor'', "thief". The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

honours James and Louise Temerty, the chairman of Northland Power and the

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...

Board of Governors A board of directors is a governing body that supervises the activities of a business, a nonprofit organization, or a government agency. The powers, duties, and responsibilities of a board of directors are determined by government regulations ...

and his wife, who have supported the museum for many years. ''Acheroraptor'' is known from the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

ROM 63777, a complete right

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

with several maxillary teeth (some isolated), and from a referred dentary (

lower jaw In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

) ROM 63778, both housed at the

Royal Ontario Museum The Royal Ontario Museum (ROM) is a museum of art, world culture and natural history in Toronto, Ontario, Canada. It is one of the largest museums in North America and the largest in Canada. It attracts more than one million visitors every year ...

, Canada. Both specimens were collected approximately four metres from one another, from the same mixed faunal bonebed that occurs in the upper part of the Hell Creek Formation of

, dating to the latest

stage of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

, immediately prior to the

Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event, also known as the K–T extinction, was the extinction event, mass extinction of three-quarters of the plant and animal species on Earth approximately 66 million years ago. The event cau ...

. The holotype specimen was collected on August 28, 2009, by commercial fossil hunters, one of whom also collected the dentary several years later, and who were later able to provide detailed geographic data from

GPS The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide geol ...

and photographs of the specimen ''

in situ is a Latin phrase meaning 'in place' or 'on site', derived from ' ('in') and ' ( ablative of ''situs'', ). The term typically refers to the examination or occurrence of a process within its original context, without relocation. The term is use ...

'' in the ground on the day of discovery. Both specimens were subsequently purchased by the Royal Ontario Museum from a private collector.

Classification

The

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

position of ''Acheroraptor'' was explored by Evans ''et al.'' (2013) using several data matrices. Both specimens of ''Acheroraptor'' were coded as a single taxon into Turner ''et al.'' (2012) data matrix, an extensive phylogenetic analysis of theropods that focuses on

maniraptora Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to ''Ornithomimus velox''. It contains the major subgroups Avialae, Dromaeosauridae, Troodontidae, ...

ns. ''Acheroraptor'' was recovered as a member of the clade containing

Eudromaeosauria Eudromaeosauria (International Phonetic Alphabet, ; "true dromaeosaurs") is a subgroup of terrestrial Dromaeosauridae, dromaeosaurid theropod dinosaurs. They were small to large-sized predators that flourished during the Cretaceous Period (geolo ...

and

Microraptorinae Microraptoria (Greek, μίκρος, ''mīkros'': "small"; Latin, ''raptor'': "one who seizes") is a clade of basal dromaeosaurid theropod dinosaurs. Definitive microraptorians lived during the Barremian to Aptian stages of the Early Cretaceous in ...

, confirming its referral to the

Dromaeosauridae Dromaeosauridae () is a family of feathered coelurosaurian theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from ...

, and possibly to Eudromaeosauria. Within that clade, however, most taxa were recovered in a large

polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tree ...

, due to the limited codings available for ''Acheroraptor''. Evans ''et al.'' (2013) also coded the specimens of ''Acheroraptor'' (together and separately) into an updated version of the smaller, dromaeosaur-specific dataset from Longrich and Currie (2009). '' Velociraptor osmolskae'' and ''

Balaur bondoc ''Balaur bondoc'' is a species of paravian theropod dinosaur from the late Cretaceous period, in what is now Romania. It is the type species of the monotypic genus ''Balaur'', after the '' balaur'' (), a dragon of Romanian folklore. The specifi ...

'' were added, '' Itemirus'' was excluded (following its identification as a

tyrannosauroid Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinen ...

by Miyashita and Currie (2009)), and following Turner ''et al.'' (2012) the codings for '' Adasaurus mongoliensis'' were separated into these based on the holotype from the

Nemegt Formation The Nemegt Formation (also known as Nemegtskaya Svita) is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. The formation consists of river channel sediments and contains fossils of fish, turtles, crocodilians ...

, and these based on IGM 100/23 from the Bayanshiree Formation. Several characters were also rescored and modified, and two maxillary characters were added to the matrix from Turner ''et al.'' (2012). This analysis yielded a more resolved topology, placing ''Acheroraptor'' in a relatively basal position within the Velociraptorinae, which was otherwise found to include only Asian dromaeosaurids. The

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below shows the phylogenetic position of ''Acheroraptor'' following this analysis. A 2022 study of eudromaeosauria reclassified ''Acheroraptor'' as a derived member of

Saurornitholestinae Eudromaeosauria (International Phonetic Alphabet, ; "true dromaeosaurs") is a subgroup of terrestrial Dromaeosauridae, dromaeosaurid theropod dinosaurs. They were small to large-sized predators that flourished during the Cretaceous Period (geolo ...

, with '' Atrociraptor'' as its sister taxon. Another study found support for ''Acheroraptor'' as a saurornitholestine, with ''Atrociraptor'' being recovered as its sister taxon again.

Paleobiology

An examination of the bite force of ''Acheroraptor'' suggests that like members of the Velociraptorinae, it was equipped with relatively weak jaws for inflicting rapid, slashing bites on smaller prey. This likewise indicates that saurornitholestines were more diverse in predation habits and ecological roles than previously assumed.

Paleoecology

''Acheroraptor'' is the youngest species of dromaeosaurid, and is from the Hell Creek Formation. The Hell Creek Formation is from the time of the Cretaceous-Paleogene Extinction Event, and has been dated to 66 ± 0.07 million years ago. Many animals and plants have been found in the Hell Creek Formation, the discovery site of ''Acheroraptor''. As it is known from the ''

Tyrannosaurus ''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 througho ...

''-''

Triceratops ''Triceratops'' ( ; ) is a genus of Chasmosaurinae, chasmosaurine Ceratopsia, ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous Period (geology), period, about 68 to 66 million years ago on the island ...

'' fauna, ''Acheroraptor'' is the youngest dromaeosaurid, along with the much larger ''

Dakotaraptor ''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 ...

''. Evans ''et al.'' found that ''Acheroraptor'' was the only dromaeosaurid from the Hell Creek Formation. Common teeth previously referred to ''

Dromaeosaurus ''Dromaeosaurus'' (; ) is a genus of Dromaeosauridae, dromaeosaurid theropod dinosaur that lived during the Late Cretaceous period (middle late Campanian and Maastrichtian), sometime between 80 and 69 million years ago, in Alberta, Canada and th ...

'' and ''

Saurornitholestes ''Saurornitholestes'' ("lizard-bird thief") is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Canada (Alberta and Saskatchewan) and the United States (Montana, New Mexico, Alabama, and South Carolina). Two spe ...

'' would then be considered ''Acheroraptor''. Evans ''et al.'' also concluded that there was probably only one dromaeosaurid in the Hell Creek-Lance assemblage. In 2015, this view was disproven, with the description of ''

'', a far larger second dromaeosaur from the formation. Other non-dromaeosaurid theropods from the formation are

tyrannosaurids Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to fifteen genera, including the eponymous ''Tyrannosaurus''. The exact number of genera i ...

, ornithomimids,

troodontids Troodontidae is a clade of bird-like theropod dinosaurs from the Late Jurassic to Late Cretaceous. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinos ...

birds Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

, and caenagnathids. The tyrannosaurids from the formation are ''

Nanotyrannus ''Tyrannosaurus'' () is a genus of large theropoda, 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 live ...

'' and ''Tyrannosaurus'', although the former might be a junior synonym of the latter. Among ornithomimids are the genera ''

Struthiomimus ''Struthiomimus'', meaning "ostrich-mimic" (from the Greek στρούθειος/''stroutheios'', or "of the ostrich", and μῖμος/''mimos'', meaning "mimic" or "imitator"), is a genus of ornithomimid dinosaurs from the late Cretaceous of Nor ...

'' as well as ''

Ornithomimus ''Ornithomimus'' (; "bird mimic") is a genus of ornithomimid theropod dinosaurs from the Campanian and Maastrichtian ages of Late Cretaceous Western North America. ''Ornithomimus'' was a swift, bipedal dinosaur which fossil evidence indicates wa ...

'', and " Orcomimus." The birds known from the formation are ''

Avisaurus ''Avisaurus'' (meaning "bird lizard") is a genus of enantiornithine avialan from the Late Cretaceous of North America. Discovery ''Avisaurus archibaldi'' was discovered in the Late Cretaceous Hell Creek Formation of North America (Maastrichtian, ...

'', ''

Brodavis ''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 ...

baileyi'', and two unnamed hesperornithoforms, possibly ''

Potamornis ''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 u ...

''. Only three

oviraptorosaurs Oviraptorosaurs ("egg thief lizards") are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot-like skulls, with or wi ...

are from the Hell Creek Formation, '' Anzu'', '' Leptorhynchos'' and third and undescribed specimen, very similar to ''

Gigantoraptor ''Gigantoraptor'' () is a genus of large oviraptorosaur dinosaur that lived in Asia during the Late Cretaceous period. It is known from the Iren Dabasu Formation of Inner Mongolia, where the first remains were found in 2005. ''Gigantoraptor'' w ...

'', from South Dakota. However, only fossilized foot prints were discovered as of 2016. The known troodontids from this formation include ''

Troodon ''Troodon'' ( ; ''Troödon'' in older sources) is a controversial genus of relatively small, bird-like theropod dinosaurs definitively known from the Campanian age of the Late Cretaceous period (about 77 million years ago). It includes at l ...

'', '' Pectinodon'', and ''

Paronychodon ''Paronychodon'' (meaning "beside claw tooth") was a 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 b ...

''. A single species of

coelurosaur Coelurosauria (; from Greek, meaning "hollow-tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, ty ...

is known from similar fossil formations includes ''

Richardoestesia ''Richardoestesia'' is a morphogenus of theropod dinosaur teeth, originally described from the Late Cretaceous of what is now Canada, the United States and Kazakhstan. It currently contains two species, ''R. gilmorei'' and ''R. isosceles'', a ...

''.

Ornithischia Ornithischia () is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek ...

ns are abundant in the Hell Creek Formation. The main groups of ornithischians are

ankylosauria Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs ...

ns,

ornithopods Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivore, herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and rel ...

ceratopsia Ceratopsia or Ceratopia ( or ; Ancient Greek, Greek: "horned faces") is a group of herbivore, herbivorous, beaked dinosaurs that thrived in what are now North America, Asia and Europe, during the Cretaceous Period (geology), Period, although ance ...

ns, and

pachycephalosauria Pachycephalosauria (; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachyceph ...

ns. One ankylosaurian and two nodosaurians are known, ''

Ankylosaurus ''Ankylosaurus'' is a genus of Thyreophora, armored dinosaur. Its fossils have been found in geological formations dating to the very end of the Cretaceous Period (geology), Period, about 68–66 million years ago, in western North America, m ...

'', ''

Denversaurus ''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 taxono ...

'' and possibly ''

Edmontonia ''Edmontonia'' is a genus of panoplosaurin nodosaurid dinosaur from the Late Cretaceous Period. It is part of the Nodosauridae, a family within Ankylosauria. It is named after the Edmonton Formation (now the Horseshoe Canyon Formation in Canada ...

''. Multiple genera of ceratopsians are known from the formation, the leptoceratopsid ''

Leptoceratops ''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 parti ...

'' and the

chasmosaurines Chasmosaurinae is a subfamily of Ceratopsidae, ceratopsid dinosaurs. They were one of the most successful groups of herbivores of their time. Chasmosaurines appeared in the early Campanian, and became extinct, along with all other non-bird, avian ...

Nedoceratops ''Nedoceratops'' (meaning "insufficient horned face") is a controversial genus of ceratopsid dinosaur from the Late Cretaceous period Lance Formation of North America. It is known only from a single skull discovered in Wyoming. Its status is the ...

'', ''

Torosaurus ''Torosaurus'' (meaning "perforated lizard", in reference to the large openings in its frill) is a genus of herbivorous Chasmosaurinae, chasmosaurine Ceratopsia, ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cret ...

'', ''Triceratops'', and ''

Tatankaceratops ''Tatankaceratops'' (meaning "Bison horn face") is a controversial genus of herbivorous ceratopsian dinosaur. It is a small chasmosaurine ceratopsian which lived during the Late Cretaceous period (latest Maastrichtian stage) in what is now Sout ...

''. Hadrosaurs are common in the Hell Creek Formation, and are known from multiple species of the ornithopod ''

Thescelosaurus ''Thescelosaurus'' ( ) is a genus of Ornithischia, ornithischian dinosaur that lived during the Late Cretaceous period (geology), period in western North America. It was named and described in 1913 by the Paleontology, paleontologist Charles W. G ...

'', and the

hadrosaurids Hadrosaurids (), also hadrosaurs or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod fami ...

Edmontosaurus ''Edmontosaurus'' ( ) (meaning "lizard from Edmonton"), with the second species often colloquially and historically known as ''Anatosaurus'' or ''Anatotitan'' (meaning "duck lizard" and "giant duck"), is a genus of hadrosaurid (duck-billed) din ...

'', and an undescribed genus similar to ''

Parasaurolophus ''Parasaurolophus'' (; meaning "beside crested lizard" in reference to ''Saurolophus'') is a genus of hadrosaurid "duck-billed" dinosaur that lived in what is now western North America and possibly Asia during the Late Cretaceous period, a ...

''. Five pachycephalosaurians have been found in the Hell Creek Formation. Among them are the derived pachycephalosaurids ''

Sphaerotholus ''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 Kirtla ...

'', ''

Stygimoloch ''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'', i ...

'', '' Dracorex'', ''

Pachycephalosaurus ''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'', ...

'', and an undescribed specimen from North Dakota. Mammals are plentiful in the Hell Creek Formation. Groups represented include

multituberculates Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct order of rodent-like mammals with a fossil record spanning over 130 million years. They first appeared in the Middle Jurassic, a ...

metatheria Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as wel ...

ns, and

eutheria Eutheria (from Greek , 'good, right' and , 'beast'; ), also called Pan-Placentalia, is the clade consisting of Placentalia, placental mammals and all therian mammals that are more closely related to placentals than to marsupials. Eutherians ...

ns. The multituberculates represented include ''

Paracimexomys ''Paracimexomys'' is a genus of extinct mammals in the extinct Multituberculata order. ''Paracimexomys'' lived during the Cretaceous period. The few fossils remains come from North America. Some Romanian fossils were also tentatively assigned to ...

'', the cimolomyids '' Paressonodon'', '' Meniscoessus'', '' Essonodon'', ''

Cimolomys ''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. The genus ''Cimolomys'' was name ...

'', '' Cimolodon'', and ''

Cimexomys ''Cimexomys'' is an extinct North American mammal that lived from the Upper Cretaceous to the Paleocene. For a while, it shared the world with dinosaurs, but outlived them. It was a member of the extinct order Multituberculata and lies within the ...

''; and the neoplagiaulacids ''

Mesodma ''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 ear ...

'', and ''

Neoplagiaulax ''Neoplagiaulax'' is a mammal genus from the Paleocene of Europe and North America. In the case of the latter continent, there may possibly be some slightly earlier, Upper Cretaceous material too. It existed in the age immediately following the e ...

''. The alphadontids '' Alphadon'', '' Protalphodon'', and '' Turgidodon'', pediomyids ''

Pediomys ''Pediomys'' is an extinct genus of pediomyid marsupial from the Late Cretaceous of North America. Naming Named in 1889 for a molar from the Lance Formation by Othniel Charles Marsh, the type species ''P. elegans'' referred to its small size ...

'', '' Protolambda'', and '' Leptalestes'', the stagodontid '' Didelphodon'', the deltatheridiid ''

Nanocuris ''Nanocuris'' is an extinct genus of Deltatheridiidae from the Cretaceous of Canada (Saskatchewan) and United States (Wyoming - Lance Formation and Hell Creek Formation).R. C. Fox, C. S. Scott, and H. N. Bryant. 2007. A new, unusual therian mamm ...

'', the herpetotheriid '' Nortedelphys'', and the glasbiid '' Glasbius'' all represent metatherians of the Hell Creek Formation. A few eutherians are known, being represented by '' Alostera'', ''

Protungulatum ''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 Cre ...

'', the cimolestids ''

Cimolestes ''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 b ...

'' and '' Batodon'', the gypsonictopsid ''

Gypsonictops ''Gypsonictops'' is an extinct genus of leptictidan mammals of the family Gypsonictopidae, which was described in 1927 by George Gaylord Simpson. Species in this genus were small mammals and the first representatives of the order Leptictida, tha ...

'', and the possible nyctitheriid '' Paranyctoides''.

References

{{Taxonbar, from=Q15215620, from2=Q17126069 Eudromaeosauria Dinosaur genera Maastrichtian dinosaurs Hell Creek Formation Dinosaurs of the United States Fossil taxa described in 2013 Taxa named by Philip J. Currie

Discovery and naming

Classification

Paleobiology

Paleoecology

See also

References