''Dromaeosaurus'' (, "running lizard") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

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

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

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

which lived during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger 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 ''creta'', the ...

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. Campanian s ...

and

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

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

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

and the western United States. The

type species In 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 species that contains the biological type specimen ...

is ''Dromaeosaurus albertensis'', which was described by

William Diller Matthew William Diller Matthew Royal Society, 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 ...

and

Barnum Brown Barnum Brown (February 12, 1873 – February 5, 1963), commonly referred to as Mr. Bones, was an American paleontologist. Named after the circus showman P. T. Barnum, he discovered the first documented remains of ''Tyrannosaurus'' during a career ...

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

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 76. ...

. Teeth attributed to this genus have been found in the

Prince Creek Formation The Prince Creek Formation is a geological formation in Alaska with strata dating to the Early Maastrichtian stage of the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, David B; et a ...

. ''Dromaeosaurus'' is the

type genus In biological taxonomy, the type genus 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-bearing type of a nominal f ...

of both

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

and

Dromaeosaurinae 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 spe ...

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

Dakotaraptor ''Dakotaraptor'' (meaning “thief from Dakota”) is a potentially chimaeric genus of large dromaeosaurid theropod dinosaur that lived in North America during the Late Cretaceous period. The remains have been found in the Maastrichtian stage of ...

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

Velociraptor ''Velociraptor'' (; ) is a genus of small dromaeosaurid dinosaur 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 the pa ...

''.

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, and 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 situa ...

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 system that empties into Hudson Bay. Red Deer River ...

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 a two hour drive east of Calgary, Alberta, Canada; or , about a half-hour drive northeast of Brooks. The park is situated in the Red Deer River valley, which is noted for its strik ...

in Alberta, Canada. The find,

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

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

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

, 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 vertebra. ...

s, a first

metacarpal In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ...

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 state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

. 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, ''"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 wastebasket taxon and a dubious genus of relatively small, bird-like dinosaurs known definitively from the Campanian age of the Late Cretaceous period (about 77 mya). It includes at least ...

''); ''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 ''Velociraptor'' (; ) is a genus of small dromaeosaurid dinosaur 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 the pa ...

'' (Barsbold 1983) Paul 1988 (''

Adasaurus ''Adasaurus'' ( ; meaning "Ada 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 Mongolia ...

''). 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 s ...

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

habitat In ecology, the term habitat summarises the array of resources, physical and 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 ...

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

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

'' was once 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 whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

, 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 which 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 of ...

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 late ...

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 f ...

. ''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 The maxilla (plural: ''maxillae'' ) in vertebrates 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 t ...

. ''Dromaeosaurus'' also had a

vein Veins are blood vessels in 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 the pulmonary and umbilical veins, both of which carry oxygenated b ...

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

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

'' and the newly discovered ''

Deinonychus ''Deinonychus'' ( ; ) is a genus of dromaeosaurid theropod dinosaur with one described species, ''Deinonychus antirrhopus''. This species, which could grow up to long, lived during the early Cretaceous Period, about 115–108 million ye ...

'', 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 A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

Dromaeosaurinae, species such as ''

Utahraptor ''Utahraptor'' (meaning "Utah's thief") is a genus of large dromaeosaurid dinosaur that lived in North America during the Early Cretaceous period. It was a heavy-built, ground-dwelling, bipedal carnivore. It contains a single species, ''Utahrap ...

'', ''

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

'' 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 t ...

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 Larry Dean Martin (December 8, 1943 – March 9, 2013) was an American vertebrate paleontologist and curator of the Natural History Museum and Biodiversity Research Center at the University of Kansas. Among Martin's work is research on the Trias ...

Peter Larson Peter Lars Larson (born 1952) is an American fossil expert and president of the Black Hills Institute of Geological Research. He led the team that excavated " Sue", one of the largest and most complete specimen of ''Tyrannosaurus rex'' found to ...

, 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 J ...

, 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 the United States (Montana, New Mexico, Alabama, North Carolina, and South Carolina). Two spec ...

'', 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 f ...

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

Tyrannosaurus ''Tyrannosaurus'' is a genus of large theropoda, theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosa ...

'', in which both ''Dromaeosaurus'' and ''Tyrannosaurus'' 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. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil disco ...

, 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 76.6 and 75.1 million years ago. Fossil remains have been found in the Can ...

'', 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 Late Cretaceous dinosaurs of North America Eudromaeosaurs Fossil taxa described in 1922 Taxa named by William Diller Matthew Taxa named by Barnum Brown Paleontology in Alberta Campanian genus first appearances Campanian genus extinctions

Discovery and naming

Description

Paleobiology

Feeding behavior

See also

Footnotes

References