''Dromaeosaurus'' (; ) is a

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 ...

that lived during 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 ...

period (middle late

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

and

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 ...

), sometime between 80 and 69 million years ago, in

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

and the western United States. 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 ''Dromaeosaurus albertensis'', which was described by

William Diller Matthew William Diller Matthew FRS (February 19, 1871 – September 24, 1930) was a vertebrate paleontologist who worked primarily on mammal fossils, although he also published a few early papers on mineralogy, petrological geology, one on botany, one on ...

and

Barnum Brown Barnum Brown (February 12, 1873 – February 5, 1963), commonly referred to as Mr. Bones, was an American paleontologist. He discovered the first documented remains of ''Tyrannosaurus'' during a career that made him one of the most famous fossil ...

1922 Events January * January 7 – Dáil Éireann (Irish Republic), Dáil Éireann, the parliament of the Irish Republic, ratifies the Anglo-Irish Treaty by 64–57 votes. * January 10 – Arthur Griffith is elected President of Dáil Éirean ...

. Its fossils were unearthed in the

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 ...

Horseshoe Canyon Formation The Horseshoe Canyon Formation is a stratigraphic unit of the Western Canada Sedimentary Basin in southwestern Alberta. It takes its name from Horseshoe Canyon, an area of badlands near Drumheller. The Horseshoe Canyon Formation is part of th ...

and

Dinosaur Park Formation The Dinosaur Park Formation is the uppermost member of the Belly River Group (also known as the Judith River Group), a major geologic unit in southern Alberta. It was deposited during the Campanian stage of the Late Cretaceous, between about 7 ...

. Teeth attributed to this genus have been found in the

Prince Creek Formation The Prince Creek Formation is a geological Formation (geology), formation in Alaska with strata dating to the Late Campanian stage of the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.Weishamp ...

. ''Dromaeosaurus'' is the

type genus In biological taxonomy, the type genus (''genus typica'') is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearin ...

of both

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 Dromaeosaurinae, which include many genera with similar characteristics to ''Dromaeosaurus'' such as possibly its closest relative ''

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 ...

''. ''Dromaeosaurus'' was heavily built, more so than other dromaeosaurs that are similar in size, like ''

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 ...

''.

Discovery and naming

Despite receiving widespread attention in popular books on dinosaurs, and the usage of a complete mounted skeleton cast in museums throughout the world, ''Dromaeosaurus'' is poorly known from actual fossils. The preparation of the popular cast by the

Tyrrell Museum The Royal Tyrrell Museum of Palaeontology (RTMP; often referred to as the Royal Tyrrell Museum) is a palaeontology museum and research facility in Drumheller, Alberta, Canada. The museum was named in honour of Joseph Burr Tyrrell, and is situated ...

was only made possible by knowledge gained from other dromaeosaurids that have been discovered more recently. The first known ''Dromaeosaurus'' remains were discovered by paleontologist

during a 1914 expedition to

Red Deer River The Red Deer River is a river in Alberta and a small portion of Saskatchewan, Canada. It is a major tributary of the South Saskatchewan River and is part of the larger Saskatchewan / Nelson River, Nelson system that empties into Hudson Bay. T ...

on behalf of the American Museum of Natural History. The area where these bones were collected is now part of

Dinosaur Provincial Park Dinosaur Provincial Park is a UNESCO World Heritage Site situated 220 kilometres (137 mi) east of Calgary, Alberta, Canada; or northeast of Brooks. The park is situated in the Red Deer River valley, which is noted for its striking badland topo ...

in Alberta, Canada. The find,

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 ...

AMNH 5356, consisted of a partial skull in length, a

mandible 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 ...

, two

hyoid The hyoid-bone (lingual-bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid-cartilage. At rest, it lies between the base of the mandible and the third cervical verte ...

s, a first

metacarpal In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular bones that form the intermediate part of the hand between the phalanges (fingers) and the carpal bones ( wrist bones), which articulate ...

and some foot bones. The skull lacked most of the top of the snout. Several other skull fragments, and about thirty isolated teeth, are known from subsequent discoveries in Alberta and

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 ...

. In 1922

and Brown named and described the

of ''Dromaeosaurus'': ''Dromaeosaurus albertensis''. The generic name is derived from the Greek (') meaning 'runner' and (') meaning 'lizard'. 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 ...

, ''"albertensis"'', refers to

. Another seven species of ''Dromaeosaurus'' were named: ''Dromaeosaurus laevifrons'' (Cope 1876) Matthew & Brown 1922; '' Dromaeosaurus cristatus'' (Cope 1876) Matthew & Brown 1922 (''

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 ...

''); ''Dromaeosaurus? gracilis'' (Marsh 1888) Matthew & Brown 1922; ''Dromaeosaurus explanatus'' (Cope 1876) Kuhn 1939; '' Dromaeosaurus minutus'' (Marsh 1892) Russell 1972 (an

alvarezsaurid Alvarezsauridae is a family of small, long-legged dinosaurs. Although originally thought to represent the earliest known flightless birds, they are now thought to be an early diverging branch of maniraptoran theropods. Alvarezsaurids were highly ...

); ''Dromaeosaurus falculus'' (Cope 1876) Olshevsky 1979 and '' Dromaeosaurus mongoliensis'' (Barsbold 1983) Paul 1988 (''

Adasaurus ''Adasaurus'' ( ; meaning "evil lizard") is a genus of dromaeosaurid dinosaur that lived in Asia during the Late Cretaceous period about 70 million years ago. The genus is known from two partial specimens found in the Nemegt Formation of Mongoli ...

''). Most of them were based on fragmentary material, some belonging to other genera, and far less complete than that of ''Dromaeosaurus albertensis'', and those that haven't been reclassified are considered ''

nomina dubia In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...

'' today. Nevertheless, it has grown apparent that ''Dromaeosaurus albertensis'' is even rarer in its

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

than other small theropods, although it was the first dromaeosaurid of which reasonably good cranial material was described. The genus ''

Chirostenotes ''Chirostenotes'' ( ; named from Ancient Greek, Greek 'narrow-handed') is a genus of oviraptorosaurian dinosaur from the late Cretaceous (about 76.5–75 million years ago) of Alberta, Canada. The type species is ''Chirostenotes pergracilis''. ...

'' was considered to be synonymous with ''Dromaeosaurus'' at one point in time.

Description

''Dromaeosaurus'' was a medium-sized

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they ar ...

, about in length and in body mass. Its mouth was full of sharp teeth, and it probably would have had a sharply curved "sickle claw" on each foot. It lived during the

stage of the

. However, some fragmentary remains such as teeth that may belong to this genus have been found from the late

age

Hell Creek 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 o ...

and

Lance Formation The Lance (Creek) Formation is a division of Late Cretaceous (dating to about 69–66 Ma) rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the lates ...

s, dating to 66 million years ago. Teeth have also been found in the

Aguja Formation The Aguja Formation is a geological formation in North America, exposed in Texas, United States and Chihuahua and Coahuila in Mexico, whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered ...

. ''Dromaeosaurus'' had a relatively robust skull with a deep snout. Its teeth were rather large and were shaped like a curved cone with a coat of enamel covering the crown. It had only nine teeth in each

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 ...

. ''Dromaeosaurus'' also had a

vein Veins () are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and feta ...

at the back of the head, the ''vena capitis dorsalis'', that drained the front neck muscles through two long canals running to the posterior surface of the brain. The

Meckelian groove The Meckelian groove (or Meckel's groove, Meckelian fossa, or Meckelian foramen, or Meckelian canal) is an opening in the medial (inner) surface of the mandible (lower jaw) which exposes the Meckelian cartilage. Matthew and Brown originally placed ''Dromaeosaurus'' to its own subfamily, the Dromaeosaurinae, within the "Deinodontidae" (now known as

Tyrannosauridae 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 ...

) based on some similarities in the general proportions of the skull. In 1969,

John H. Ostrom John Harold Ostrom (February 18, 1928 – July 16, 2005) was an American paleontologist who revolutionized the modern understanding of dinosaurs. Ostrom's work inspired what his pupil Robert T. Bakker has termed a " dinosaur renaissance". Begin ...

recognized that ''Dromaeosaurus'' shared many features with ''

'' and the newly discovered ''

Deinonychus ''Deinonychus'' ( ; ) is a genus of Dromaeosauridae, dromaeosaurid Theropoda, theropod dinosaur with one described species, ''Deinonychus antirrhopus''. This species, which could grow up to long, lived during the early Cretaceous Period (ge ...

'', and assigned these forms to a new family:

. Since then, many new relatives of ''Dromaeosaurus'' have been found. The exact relationships of ''Dromaeosaurus'' are somewhat unclear. Although its rugged build gives it a primitive appearance, it was actually a very specialized animal. In an analysis of the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

Dromaeosaurinae, species such as ''

Utahraptor ''Utahraptor'' (meaning "Utah's predator") is a genus of large dromaeosaurid (a group of feathered carnivorous theropods) dinosaur that lived during the Early Cretaceous period from around 139 to 135 million years ago in what is now the United ...

'', ''

Achillobator ''Achillobator'' ( ; meaning "Achilles hero") is a genus of large dromaeosaurid theropod dinosaur that lived during the Late Cretaceous period about 96 million to 89 million years ago in what is now the Bayan Shireh Formation of Mongolia. The ge ...

'' and ''

Yurgovuchia ''Yurgovuchia'' (meaning "coyote") is a genus of dromaeosaurid theropod dinosaurs that lived in North America during the Early Cretaceous period in what is now the Cedar Mountain Formation. It contains a single species, ''Yurgovuchia doellingi''. ...

'' have been recovered. The genus ''Dakotaraptor'' has been classified as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to ''Dromaeosaurus'', but more recent analysis do not recover such a close relationship. Below is a cladogram by Senter ''et al.'' in 2012. ''Dromaeosaurus'' is recovered as the sister taxon to ''Yurgovuchia'', ''Utahraptor'' and ''Achillobator''. Dromaeosaurs

The cladogram below follows a 2015 analysis by paleontologists Robert DePalma, David Burnham, Larry Martin,

Peter Larson Peter Lars Larson (born 1952) is an American fossil dealer who is head of the Black Hills Institute of Geological Research, which specialises in the excavation and preparation of fossils. He led the team that excavated " Sue", one of the largest ...

, and

Robert Bakker Robert Thomas Bakker (born March 24, 1945) is an American paleontologist who helped reshape modern theories about dinosaurs, particularly by adding support to the theory that some dinosaurs were endothermic (warm-blooded). Along with his mentor ...

, using updated data from the Theropod Working Group. In this analysis, ''Dromaeosaurus'' is classified as the sister taxon of ''Dakotaraptor''.

Paleobiology

''Dromaeosaurus'' differs from most of its relatives in having a short, massive skull, a deep mandible, and robust teeth. The teeth tend to be more heavily worn than those of its relative ''

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 ...

'', suggesting that its jaws were used for crushing and tearing rather than simply slicing through flesh. Therrien ''et al.'' (2005) estimated that ''Dromaeosaurus'' had a bite nearly three times as powerful as that of ''Velociraptor'' and suggested it relied more on its jaws than on the sickle claw to kill its prey. In a study predominantly centered around ''

Shuvuuia ''Shuvuuia'' is a genus of bird-like theropod dinosaur from the late Cretaceous period of Mongolia. It is a member of the family Alvarezsauridae, small coelurosaurian dinosaurs which are characterized by short but powerful forelimbs specialized ...

'', ''Dromaeosaurus'' was compared to the former and also to ''

Alioramus ''Alioramus'' (; meaning 'different branch') is a genus of tyrannosaurid theropod dinosaurs from the Late Cretaceous period of Asia. It currently contains two species. The type species, ''A. remotus'' is known from a partial skull and three foo ...

'', in which both ''Dromaeosaurus'' and ''Alioramus'' were discovered to be diurnal predators.

Feeding behavior

''Dromaeosaurus feeding habits were also discovered to be typical of coelurosaurian theropods, with a characteristic "puncture and pull" feeding method. Studies of wear patterns on the teeth of this animal by Angelica Torices ''et al.'' in a study regarding theropod feeding habits indicate that dromaeosaurid teeth share similar wear patterns to those seen in the Tyrannosauridae and

Troodontidae 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 ...

, respectively. However, micro-wear on the teeth indicated that ''Dromaeosaurus'' likely preferred larger prey items than the troodontids it shared their environment with. Such differentiations in its diet likely allowed the theropod to inhabit the same environment as its more distant maniraptoran relatives. The same study also indicated that both ''Dromaeosaurus'' and ''Saurornitholestes'' (also analyzed in the study) likely included bone in their diet and were better adapted to handle the stresses associated with attacking struggling prey while troodontids, equipped with weaker jaws, preyed on softer animals and prey items such as invertebrates and carrion. This feeding strategy and ability to handle struggling prey was also a feature that the theropod also shared with tyrannosaurids such as ''

Gorgosaurus ''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.5 and 75 million years ago. Fossil remains have been found in the Ca ...

'', which was also analyzed in said study alongside these smaller theropods.

Footnotes

References

* * * * Larsson, H.C.E. 2001. Endocranial anatomy of ''Carcharodontosaurus saharicus'' (Theropoda: Allosauroidea) and its implications for theropod brain evolution. pp. 19–33. In: ''Mesozoic Vertebrate Life''. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press. * * * * * * Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): ''The Dinosauria'', 2nd, Berkeley: University of California Press. 861 pp. . {{Taxonbar, from=Q131082 Eudromaeosauria Dinosaur genera Campanian dinosaurs Maastrichtian dinosaurs Dinosaur Park Formation Horseshoe Canyon Formation Fossil taxa described in 1922 Taxa named by William Diller Matthew Taxa named by Barnum Brown Dinosaurs of Canada

Discovery and naming

Description

Paleobiology

Feeding behavior

See also

Footnotes

References