Balaur bondoc

Balaur Temporal range: Late Cretaceous,
Balaur bondoc displaying its unusual double sickle claws in a kicking motion
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	Dinosauria
Order:	Saurischia
Suborder:	Theropoda
Infraorder:	†Deinonychosauria
Family:	†Dromaeosauridae
Subfamily:	†Velociraptorinae
Genus:	†Balaur Csiki et al., 2010
Species
B. bondoc Csiki et al., 2010 (type)

Balaur bondoc (Romanian pronunciation: [baˈla.ur bonˈdok]) is a uniquely specialized species of carnivorous (theropod) dinosaur from the late Cretaceous. It was described by scientists in August 2010, and was named after the balaur, a dragon of Romanian folklore. It is known from a single partial skeleton representing the type specimen. Having been described as a "beefy version of the predatory Velociraptor", its name is Romanian for 'stocky dragon'.

Seventy million years ago, world sea levels were higher, and the location where its fossils are found was an off-shore part of the European archipelago called Haţeg Island. Unlike its other relatives within the dromaeosaur family, which includes Velociraptor, Deinonychus, and the four-winged Microraptor gui, this raptor had not just one but two large, retractable, sickle-shaped claws on each foot, and its limbs were proportionally shorter and heavier than those of its other relatives. Given these and nearly twenty other derived traits, the new genus Balaur was created for this one species. As with other dinosaurs from Haţeg, such as Magyarosaurus, a dwarf sauropod known from Romania, its aberrant features are argued to show the effects of its island habitat on its evolution.

Description

Balaur is a dromaeosaurid theropod dinosaur estimated to have lived about 70 million years ago in the late Cretaceous (Maastrichtian). Its bones were shorter and heavier than those of other dromaeosaurs. While the feet of most dromaeosaurs bore a single, large "sickle claw" on the second toe which was held retracted off the ground, Balaur had large retractable sickle claws on both the first and second toes of each foot. In addition to its strange feet, Balaur is unique for its status of being the most complete nonavialan theropod from the late Cretaceous of Europe. It also possesses a great number of additional autapomorphies, including a reduced and presumably nonfunctional third manual digit.

File:LateCretaceousGlobal.jpg

Much of the land now forming Europe was submerged during the Cretaceous.

Balaur bondoc compared in size to a human

The partial skeleton—which consists of a variety of vertebrae as well as much of pectoral and pelvic girdles and the limbs—was collected from the red floodplain mudstone of the Sebeş Formation of Romania. It is the first reasonably complete and well-preserved theropod from the Late Cretaceous of Europe.

During the Maastrichtian much of Europe was fragmented into islands, and a number of the animal's bizarre features are thought to be a result of the relatively isolated conditions imposed on many of the populations in this area. Species which are isolated on islands can be subject to the effects of genetic drift and the founder effect which can magnify the effect of mutations which might be diluted in a larger population. Other island effects such as Foster's rule, which describes how small mainland species become larger and large mainland species become smaller, can take effect. Cretaceous Romania is known, for example, for its dwarf sauropods. Phylogenetic analysis currently places Balaur closest to the Asiatic mainland species Velociraptor to which it is similar in size, with Balaur's recovered skeletal elements suggesting an overall length of around 1.8 m to 2.1 m. Hence, in this case, Foster's effect is not evinced. Yet, when compared to its nearest relatives, some 20 unique features were observed, including a re-evolved functional first toe with a large claw that can be hyperextended, short and stocky feet and legs, and large muscle attachment areas on the pelvis which indicate that it was adapted for strength rather than speed. Csiki et al. describe this "novel body plan" as "a dramatic example of aberrant morphology developed in island-dwelling taxa."

Discovery

The first small bones belonging to Balaur bondoc, six elements of the front limbs, specimens FGGUB R. 1580-1585, were discovered in 1997 in Romania by Dan Grigorescu, but the morphology of the arm was so unusual that scientists could not correctly combine them, mistaking them for the remains of a oviraptorosaur. The first partial skeleton was discovered in September 2009 in Romania, approximately 2.5 kilometers north of Sebeş, along the Sebeş river in the Sebeş Formation dating from the early Maastrichtian and was given the preliminary field number SbG/A-Sk1. Later it received the holotype inventory number EME VP.313. The discovery was made by the geologist and paleontologist Mátyás Vremir of the Transylvanian Museum Society of Cluj Napoca who sent them for analysis to Zoltán Csiki of the University of Bucharest. The findings were described on August 31, 2010, in the Proceedings of the National Academy of Sciences. The 1997 specimens indicate an individual about 45% longer than the holotype; also they were found in a younger stratum.

The generic name Balaur (three syllables, stressed on the second /a/) is from the Romanian for a dragon of Romanian folklore, while the specific name bondoc (pronounced like "boned oak", meaning "a squat, chubby individual") refers to the small, robust shape of the animal. As the balaur is a winged dragon, the name additionally hints at the close relation of Balaur to the birds within Panaves. Bondoc also has a secondary connotation: derived from the Turkish bunduk, "small ball", it alludes to the probable Asian origin of the ancestors of Balaur.

Behavior

Little is known about the behavior of Balaur, but Csiki speculates that it may have been one of the apex predators in its limited island ecosystem, because no larger teeth have ever been found in Romania. He also believes that it likely used its double sickle claws for slashing prey, and that the atrophied state of its hands indicates that it probably did not use them to hunt. One of the original discoverers indicated that it "was probably more of a kickboxer than a sprinter" compared to Velociraptor, and was probably able to hunt larger animals than itself. However, the hunting behavior as well as its typical prey are not known.

External links

• "'Stocky dragon' dinosaur terrorized Late Cretaceous Europe" article from PhysOrg.com