In Depth
The dromaeosaurids are a very popular group of dinosaurs that all share a few common features. These include reasonably lightweight build, long stiff tails for balance, legs and pelvis adapted for very fast running and a large sickle shaped claw on the second toe of each foot. Balaur however is a dromaeosaur with a difference; instead of having one sickle shaped claw on each foot it had two. These claws were on the second and first toes, and seem to be the principal killing weapons since the hands are known to have one digit less than most other known dromaeosaurids.
In popular fiction the large sickle claws are usually interpreted as slashing weapons that could open up the side of an animal in a single stroke, an idea based upon very early ideas about dinosaurs like Balaur. However more modern analysis has produced scenarios where the sickle claws are more suited to stabbing rather than slashing. Additionally they may have also been used for getting a grip onto similarly sized or larger prey, and in the case of Balaur, the two sickle claws may have been to compensate for a lack of one of the hand digits.
Balaur has a number of other distinctive features that distinguish it from other dromaeosaurids, but overall it seems to have been more heavily built than its relatives. Palaeontologists are able to tell this because the bones, particularly those of the limbs, are shorter and more robust than in the closest relatives. This suggests that Balaur was built for power rather than high speed. It is curious that a dinosaur from a typically fast and lightweight family line would deviate so much from the others, but the reasons for why may be down to environmental factors from where it lived.
So far Balaur remains have only been found in Romania from a part that back in the late Cretaceous period was actually separated from the mainland. Today we now call this landmass Hateg Island (after the Hateg Basin, which it would form after its collision with mainland Europe), and this island is particularly noted for the large variety of dinosaurs that have been recovered from there. The most interesting fact about this dinosaur is that they included varieties such as sauropods and ornithopod hadrosauroids. On the mainland these varieties could comfortably grow up to ten meters long and probably more for certain genera, but on Hateg Island the typically large dinosaurs like sauropods grew much smaller than their mainland relatives.
The reason for this is a process called insular dwarfism. Island ecosystems are fragile because there is a reduced land mass for plants to grow upon. This means that herbivorous animals that feed upon plants have less food, and no option to search elsewhere because they are surrounded by so many miles of sea, they cannot reach other areas upon the mainland. Another factor to consider is that for a species of herbivores to survive, you need many individuals, perhaps as many as a few hundred to avoid any negative effects on inbreeding. The one logical result for large animals that find themselves living in such restricted ecosystems is that they grow smaller, something that means they do not need to eat so much food, so they don’t exhaust the available supply.
With an estimated size around the two meter mark, Balaur does not seem to have grown small by insular dwarfism, many mainland varieties of dromaeosaur also grew to this size with some being larger, and some even being smaller. But on Hateg Island Balaur would have had access to dwarf sauropods like Magyarosaurus and hadrosaurids like Telmatosaurus. Although much smaller than their mainland counterparts, these types of herbivorous dinosaurs would have still been quite powerfully built, and arguably not that fast, at least when compared to a dromaeosaurid like Balaur. This could be where the more muscular legs and double sickle claws on each foot could have come in; they would have given dinosaurs like Balaur a significant edge when attacking them. Additionally in the absence of large theropods like those known in larger continental landmasses, dromaeosaurids like Balaur would have found itself elevated to the status of apex predator for the ecosystems.
The name Balaur is a reference to a dragon in Romanian folklore. Although many prehistoric animals have been after dragons (for example the archosaur Smok was named after a dragon in Polish folkore) the name has a double meaning since dragons are seen as winged flying creatures, and dromaeosaurid dinosaurs are treated as being very close to the ancestors of birds. The type species name B. bondoc means ‘boned oak’ and is based upon the squat appearance of the holotype remains. Out of all the other dromaeosaurids, Balaur is considered to be most closely related to those like Velociraptor from Asia.*Special note - While Hateg Island is especially well noted for its dwarf dinosaurs, at least one giant has been found there. This refers to the pterosaur Hatzegopteryx, and although known from only partial remains, these indicate that it was one of the largest pterosaurs of all time.
Further Reading
– An aberrant island-dwelling theropod dinosaur from the Late Cretaceous of Romania – Proceedings of the National Academy of Sciences 107(35):15357-15361 – Z. Csiki, M. Vremir, S. L. Brusatte & M. A. Norell – 2010. – The Osteology of Balaur bondoc, an Island-Dwelling Dromaeosaurid (Dinosauria: Theropoda) from the Late Cretaceous of Romania – Bulletin of the American Museum of Natural History 374: 1-100. – S. L. Brusatte, M. T. S. Vremir, Z. N. Csiki-Sava, A. H. Turner, A. Watanabe, G. M. Erickson & M. A. Norell – 2013.
