Acheroraptor Temporal range: Late Cretaceous (Maastrichtian), | |
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Casts of the holotype maxilla and referred dentary, National Museum of Natural History. | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Clade: | Pennaraptora |
Clade: | Paraves |
Family: | † Dromaeosauridae |
Genus: | † Acheroraptor Evans et al., 2013 |
Type species | |
†Acheroraptor temertyorum Evans et al., 2013 |
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 Dakotaraptor , which is also known from Hell Creek. A basal cousin of Velociraptor, Acheroraptor is known from upper and lower jaw material.
Acheroraptor was first described and named by David C. Evans, Derek W. Larson and Philip J. Currie in 2013 and the type species is Acheroraptor temertyorum. The generic name is derived from the Greek Ἀχέρων, Acheron, "underworld", in reference to the provenance from the Hell Creek Formation, and the Latin raptor, "thief". The specific name honours James and Louise Temerty, the chairman of Northland Power and the ROM Board of Governors and his wife, who have supported the museum for many years. [1]
Acheroraptor is known from the holotype ROM 63777, a complete right maxilla with several maxillary teeth (some isolated), and from a referred dentary (lower jaw) ROM 63778, both housed at the Royal Ontario Museum, 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 Montana, dating to the latest Maastrichtian stage of the Late Cretaceous, immediately prior to the Cretaceous–Paleogene extinction event. 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 and photographs of the specimen in situ in the ground on the day of discovery. Both specimens were subsequently purchased by the Royal Ontario Museum from a private collector. [1]
The phylogenetic 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 maniraptorans. Acheroraptor was recovered as a member of the clade containing Eudromaeosauria and Microraptorinae, confirming its referral to the Dromaeosauridae, and possibly to Eudromaeosauria. Within that clade, however, most taxa were recovered in a large polytomy, due to the limited codings available for Acheroraptor. [1]
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 were added, Itemirus was excluded (following its identification as a tyrannosauroid 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, 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 below shows the phylogenetic position of Acheroraptor following this analysis. [1]
Dromaeosauridae |
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A 2022 study of eudromaeosauria reclassified Acheroraptor as a derived member of Saurornitholestinae, with Atrociraptor as its sister taxon. [2]
Acheroraptor is the youngest species of dromaeosaurid, and is from the Hell Creek Formation. [1] 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. [3] Many animals and plants have been found in the Hell Creek Formation, [4] the discovery site of Acheroraptor. As it is known from the Tyrannosaurus - Triceratops fauna, Acheroraptor is the youngest dromaeosaurid, along with the much larger Dakotaraptor . [1] [5]
Evans et al. found that Acheroraptor was the only dromaeosaurid from the Hell Creek Formation. Common teeth previously referred to Dromaeosaurus and Saurornitholestes would then be considered Acheroraptor. Evans et al. also concluded that there was probably only one dromaeosaurid in the Hell Creek-Lance assemblage. [1] In 2015, this view was disproven, with the description of Dakotaraptor , a far larger second dromaeosaur from the formation. [5] Other non-dromaeosaurid theropods from the formation are tyrannosaurids, ornithomimids, troodontids, [4] birds, [6] and caenagnathids. [7] The tyrannosaurids from the formation are Nanotyrannus and Tyrannosaurus, although the former might be a junior synonym of the latter. Among ornithomimids are the genera Struthiomimus as well as Ornithomimus , [4] and "Orcomimus." [8] The birds known from the formation are Avisaurus , [4] Brodavis baileyi, [9] and two unnamed hesperornithoforms, possibly Potamornis . [6] Only three oviraptorosaurs are from the Hell Creek Formation, Anzu , Leptorhynchos [7] and third and undescribed specimen, very similar to Gigantoraptor , from South Dakota. However, only fossilized foot prints were discovered as of 2016. [10] The known troodontids from this formation include Troodon , Pectinodon , and Paronychodon . A single species of coelurosaur is known from similar fossil formations includes Richardoestesia .
Ornithischians are abundant in the Hell Creek Formation. The main groups of ornithischians are ankylosaurians, ornithopods, ceratopsians, and pachycephalosaurians. One ankylosaurian and two nodosaurians are known, Ankylosaurus , Denversaurus and possibly Edmontonia . Multiple genera of ceratopsians are known from the formation, the leptoceratopsid Leptoceratops and the chasmosaurines Nedoceratops , Torosaurus , Triceratops, [4] and Tatankaceratops . [11] Hadrosaurs are common in the Hell Creek Formation, and are known from multiple species of the ornithopod Thescelosaurus , and the hadrosaurids Edmontosaurus , [4] [12] and an undescribed genus similar to Parasaurolophus . Five pachycephalosaurians have been found in the Hell Creek Formation. Among them are the derived pachycephalosaurids Sphaerotholus , Stygimoloch , [4] Dracorex , [13] Pachycephalosaurus , [4] and an undescribed specimen from North Dakota.
Mammals are plentiful in the Hell Creek Formation. Groups represented include multituberculates, metatherians, and eutherians. The multituberculates represented include Paracimexomys , [14] the cimolomyids Paressonodon , [15] Meniscoessus , Essonodon , Cimolomys , Cimolodon , and Cimexomys ; and the neoplagiaulacids Mesodma , and Neoplagiaulax . The alphadontids Alphadon , Protalphodon , and Turgidodon , pediomyids Pediomys , [14] Protolambda , and Leptalestes , [16] the stagodontid Didelphodon , [14] the deltatheridiid Nanocuris , the herpetotheriid Nortedelphys , [15] and the glasbiid Glasbius all represent metatherians of the Hell Creek Formation. A few eutherians are known, being represented by Alostera , [14] Protungulatum , [16] the cimolestids Cimolestes and Batodon , the gypsonictopsid Gypsonictops , and the possible nyctitheriid Paranyctoides . [14]
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 in what is now 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 literally means 'three-horned face', is derived from the Greek words trí- meaning 'three', kéras meaning 'horn', and ṓps meaning 'face'.
Troodon is a former wastebasket taxon and a potentially dubious genus of relatively small, bird-like theropod dinosaurs definitively known from the Campanian age of the Late Cretaceous period. It includes at least one species, Troodon formosus, known from Montana. Discovered in October 1855, T. formosus was among the first dinosaurs found in North America, although it was thought to be a lizard until 1877. Several well-known troodontid specimens from the Dinosaur Park Formation in Alberta were once believed to be members of this genus. However, recent analyses in 2017 have found this genus to be undiagnostic and referred some of these specimens to the genus Stenonychosaurus some to the genus Latenivenatrix, and some to the genus Pectinodon. The genus name is Ancient Greek for "wounding tooth", referring to the teeth, which were different from those of most other theropods known at the time of their discovery. The teeth bear prominent, apically oriented serrations. These "wounding" serrations, however, are morphometrically more similar to those of herbivorous reptiles, and suggest a possibly omnivorous diet.
Dromaeosaurus is a genus of dromaeosaurid theropod dinosaur that lived during the Late Cretaceous period, sometime between 80 and 69 million years ago, in Alberta, Canada and the western United States. The type species is Dromaeosaurus albertensis, which was described by William Diller Matthew and Barnum Brown in 1922. Its fossils were unearthed in the Dinosaur Park Formation. Teeth attributed to this genus have been found in the Prince Creek Formation. Dromaeosaurus is the type genus of both Dromaeosauridae and Dromaeosaurinae, which include many genera with similar characteristics to Dromaeosaurus such as possibly its closest relative Dakotaraptor. Dromaeosaurus was heavily built, more so than other dromaeosaurs that are similar in size, like Velociraptor.
Saurornitholestes is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Canada (Alberta) and the United States.
Pachycephalosaurus is a genus of pachycephalosaurid ornithischian dinosaur. The type species, P. wyomingensis, is the only known species, but some researchers argue that the genus Stygimoloch might be a second species, P. spinifer or a juvenile specimen of P. wyomingensis. 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. The species is known mainly from a single skull, plus a few extremely thick skull roofs. More complete fossils would come to be found in the following years.
Atrociraptor is a genus of saurornitholestine dromaeosaurid theropod dinosaur from the Late Cretaceous of Alberta, Canada.
Philip John Currie is a Canadian palaeontologist and museum curator who helped found the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta and is now a professor at the University of Alberta in Edmonton. In the 1980s, he became the director of the Canada-China Dinosaur Project, the first cooperative palaeontological partnering between China and the West since the Central Asiatic Expeditions in the 1920s, and helped describe some of the first feathered dinosaurs. He is one of the primary editors of the influential Encyclopedia of Dinosaurs, and his areas of expertise include theropods, the origin of birds, and dinosaurian migration patterns and herding behavior. He was one of the models for palaeontologist Alan Grant in the film Jurassic Park.
Chirostenotes is a genus of oviraptorosaurian dinosaur from the late Cretaceous of Alberta, Canada. The type species is Chirostenotes pergracilis.
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 stretches over portions of Montana, North Dakota, South Dakota, and Wyoming. In Montana, the Hell Creek Formation overlies the Fox Hills Formation. The site of Pompeys Pillar National Monument is a small isolated section of the Hell Creek Formation. In 1966, the Hell Creek Fossil Area was designated as a National Natural Landmark by the National Park Service.
Zapsalis is a genus of dromaeosaurine theropod dinosaurs. It is a tooth taxon, often considered dubious because of the fragmentary nature of the fossils, which include teeth but no other remains.
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, known only from teeth.
Dromaeosaurinae is a subfamily of the theropod group Dromaeosauridae. The earliest dromaeosaurine is Utahraptor, dating back to the Early Cretaceous period in North America, however, some isolated teeth seems to represent an indeterminate species of dromaeosaurine, coming from the Late Jurassic period in Africa. If true, this will push their range to the Jurassic period, instead of the Cretaceous, as in most dromaeosaurs.
Austroraptor is a genus of dromaeosaurid theropod dinosaur that lived during the Campanian and Maastrichtian ages of the Late Cretaceous period in what is now Argentina.
This is an overview of the fossil flora and fauna of the Maastrichtian-Danian Hell Creek Formation.
Eudromaeosauria is a subgroup of terrestrial dromaeosaurid theropod dinosaurs. They were small to large-sized, feathered hypercarnivores that flourished in the Cretaceous Period.
Tatankaceratops is a controversial genus of herbivorous ceratopsian dinosaur. It is a small chasmosaurine ceratopsian which lived during the Late Cretaceous period in what is now South Dakota. It is known from a single partial skull which was collected from the Hell Creek Formation, dating to 66 million years ago. Tatankaceratops was described by Christopher J. Ott and Peter L. Larson in 2010 and the type species is Tatankaceratops sacrisonorum. Tatankaceratops is known from one specimen housed at the Black Hills Institute, BHI 6226.
This timeline of dromaeosaurid research is a chronological listing of events in the history of paleontology focused on the dromaeosaurids, a group of sickle-clawed, bird-like theropod dinosaurs including animals like Velociraptor. Since the Native Americans of Montana used the sediments of the Cloverly Formation to produce pigments, they may have encountered remains of the dromaeosaurid Deinonychus hundreds of years before these fossils came to the attention of formally trained scientists.
Dakotaraptor is a potentially chimaeric genus of large dromaeosaurid 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 one of the last surviving dromaeosaurids. The remains of D. steini were discovered in a multi-species bonebed. Elements of the holotype and referred specimens were later found to belong to trionychid turtles and further analysis of potential non-dromaeosaurid affinities of the holotype and referred material have not yet been conducted. Phylogenetic analyses of D. steini place it in a variety of positions within Dromaeosauridae.
Dineobellator is a genus of dromaeosaurid theropod dinosaur that lived in North America during the Late Cretaceous period 68 million years ago. The remains have been found in the Maastrichtian stage of the Naashoibito Member at the Ojo Alamo Formation, New Mexico.