Dromaeosaurus

*Dromaeosaurus albertensis*

***Dromaeosaurus*** was a genus of theropod dinosaur which lived during the Late Cretaceous period (middle late Campanian), sometime between 76.5 and 74.8 million years ago, in the western United States and Alberta, Canada. The name means 'running lizard' and is derived from the Greek *dromeus* (*δρομευς*) meaning 'runner' and *sauros* (*σαυρος*) meaning 'lizard'. though most experts nowadays conclude that dromaeosaurs were comparatively robust and likely short distance runners.

## 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 surprisingly poorly known from actual fossils. The preparation of the popular cast by the Tyrrell Museum 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 Barnum Brown during a 1914 expedition to 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 in Alberta, Canada. The find consisted of a partial skull 24 cm (9.4 in) in length, and some foot bones. Several other skull fragments, and about 30 isolated teeth, are known from subsequent discoveries in Alberta and Montana.

Several species of *Dromaeosaurus* have been described, but *Dromaeosaurus albertensis* is the most complete specimen. Additionally, it is apparent that this genus is even rarer than other small theropods, although it was one of the first small theropods described based on reasonably good cranial material.

Matthew and Brown originally placed *Dromaeosaurus* within "Deinodontidae" (now known as Tyrannosauridae), based on some similarities in the general proportions of the skull. In 1969, John H. Ostrom recognized that *Dromaeosaurus* shared many features with *Velociraptor* and the newly-discovered *Deinonychus*, and assigned these forms to a new family: Dromaeosauridae. Since then, many new relatives of *Dromaeosaurus* have been found.

## Description

*Dromaeosaurus* was a small carnivore, about 2 m (6 feet 7 inches) in length and 15 kilograms (33 lbs) in weight. Its mouth was full of sharp teeth, and it had a sharp "sickle claw" on each foot. It lived during the Campanian stage of the Late Cretaceous, however, some fragmentary remains such as teeth which may belong to this genus have been found from the late Maastrichtian age Lance and Hell Creek Formations, dating to 66.038 million years ago. *Dromaeosaurus* had a relatively robust skull with a deep snout. Its teeth were rather large and it had only nine of them in the maxilla. In *Dromaeosaurus albertensis*, a vein at the back of the head, the vena capitis dorsalis, drains the front neck muscles through two long canals running to the posterior surface of the brain.

Although only a few bones are known from the hindlimb, they indicate that *Dromaeosaurus* was a powerfully built animal. The presence of feathers in closely related animals makes it extremely likely that it was feathered as well.

*Dromaeosaurus* had remarkably large eyes and excellent vision. It also probably had a good sense of smell and hearing. Its neck was curved flexible and its jaws were solidly built. The tail was flexible at the base but sheathed in a lattice of bony rods; this allowed it to be carried in a sharply upturned position.

## Classification

Matthew and Brown originally placed *Dromaeosaurus* to its own subfamily, the Dromaeosaurinae, within the "Deinodontidae" (now known as Tyrannosauridae) based on some similarities in the general proportions of the skull. In 1969, John H. Ostrom recognized that *Dromaeosaurus* shared many features with *Velociraptor* and the newly discovered *Deinonychus*, and assigned these forms to a new family: Dromaeosauridae. 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 Dromaeosaurinae, species such as *Utahraptor*, *Achillobator* and *Yurgovuchia* have been recovered. The genus *Dakotaraptor* has been classified as the sister taxon 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*.

The cladogram below follows a 2015 analysis by paleontologists Robert DePalma, David Burnham, Larry Martin, Peter Larson, and Robert Bakker, 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*, 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*.

It is possible that *Dromaeosaurus* was more of a scavenger than other small theropods, or it may be that *Dromaeosaurus* relied more heavily on its jaws to dispatch its prey. It was probably better suited to tackling large prey than the more lightly built *Saurornitholestes*.

## Relationships

The relationships of *Dromaeosaurus* are unclear. Although its rugged build gives it a primitive appearance, it was actually a very specialized animal. It is usually given its own subfamily, the Dromaeosaurinae; this group is thought to include *Utahraptor*, *Achillobator*, *Adasaurus* and perhaps *Deinonychus*.

However, the relationships of dromaeosaurs are still in a state of flux. "Dromaeosaurus Morphotype A" is the designation given to a series of unusual, ridged dromaeosaur teeth from Alberta. These teeth probably do not belong to *Dromaeosaurus*, although it is unclear from what animal they do come.

## JPInstitute.com Description

Dromaeosaurus was the original raptor. It was a small, vicious hunter that had a mouth full of serrated, razor-sharp teeth and a sharp, hooked claw on each foot that it used to clamp down on its victims.

When first discovered, Dromaeosaurus was hard to classify. It had such large foot bones that it was thought to be a much larger dinosaur. It had a large brain for its size, large eyes and grasping hands. Because of this, scientists thought that it was more than twice its actual size. It wasn't until almost 50 years after the discovery of the type specimen that it was formally classified into its own family. All the other raptor dinosaurs, such as Deinonychus and Velociraptor, are members of the dromaeosaur family.

## Links

https://web.archive.org/web/20031007203639/http://www.jpinstitute.com/dinopedia/dinocards/dc\_droma.html

## Further reading

* Dixon, Dougal (2006). The Illustrated Encyclopedia of Dinosaurs (Lorenz Books): 200-201.
* Colbert, E. and D. A. Russell (1969). The small Cretaceous dinosaur *Dromaeosaurus*. *American Museum Novitates* 2380: 1-49.
* Currie, P. J., K. J. Rigby, et al. (1990). Theropod teeth from the Judith River Formation of southern Alberta, Canada. Dinosaur Systematics: Perspectives and Approaches. P. J. Currie and K. Carpenter. Cambridge, Cambridge University Press: 107-125.

## References

1. ↑ 1.0 1.1 1.2 1.3 Template:Cite journal
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5. ↑ 5.0 5.1 Template:Cite journal
6. ↑ 6.0 6.1 Template:Cite journal
7. ↑ Template:Cite book