Named specimens FGGUB R. 1580–1585, these 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,[6][7] mistaking them for the remains of an oviraptorosaur.

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 species name bondoc was chosen by the discoverers also because it is derived from the Turkish bunduk, "small ball", thus alluding to the probable Asian origin of the ancestors of Balaur.

[11] Balaur is a genus of theropod dinosaurs estimated to have lived about 70 million years ago in the late Cretaceous (Maastrichtian), and contains the single species B.

[10] In addition to its strange feet, the type specimen of Balaur is unique for its status of being the most complete theropod fossil from the late Cretaceous of Europe.

It also possesses a great number of additional autapomorphies, including a reduced and presumably nonfunctional third finger, consisting of only one rudimentary phalanx.

[10] It is similar in size to Velociraptor, with Balaur's recovered skeletal elements suggesting an overall length of around 1.8–2.5 m (5.9–8.2 ft) and a body mass of 15 kg (33 lb).

It had 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.

The initial phylogenetic analysis placed Balaur bondoc closest to the Asiatic mainland dromaeosaurid species Velociraptor mongoliensis.

[16] An independent analysis using an expanded version of the original data set (the one that found Balaur to be a dromaeosaurid) drew a similar conclusion in 2014.

[17] In 2015, researchers Andrea Cau, Tom Brougham, and Darren Naish published a study which specifically attempted to clarify which theropods were close relatives of Balaur.

While their analysis could not completely rule out the possibility that B. bondoc was a dromaeosaurid, they concluded that this result was less likely than the classification of Balaur as a non-pygostylian avialan based on several important bird-like features.

They also noted similarities with Gargantuavis and Elopteryx, indicating that the three taxa form a clade native to the Late Cretaceous European archipelago.

Csiki speculated in 2010 that it may have been one of the apex predators in its limited island ecosystem, as neither the skeletons nor teeth of larger theropods have been discovered in Romania.

[12][25] However, more recent studies by Denver Fowler and others have shown that the foot anatomy of paravians like Balaur indicate that they used their large claws to grip and pin prey to the ground while flapping with their proto-wings to stay on top of their victim.

These characteristics are consistent with the relatively short, stocky limbs and wide, swept-back pubis, which may indicate enlarged intestines for digesting vegetation as well as reduced speed.

This is also indicated by the reduced third finger, the lack of a ginglymoid lower articulation of the second metatarsal and the rather small and moderately recurved second toe claw.

[11] In 2013, it was claimed that Balaur was the only predatory vertebrate known to have become more robust after invading an island niche and it was suggested that its broad feet had evolved to improve postural stability.