Balaur bondoc

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Balaur bondoc
Temporal range:
Ma
↓
Holotype specimen
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Paraves
Genus: †Balaur
Csiki et al., 2010
Species:
†B. bondoc
Binomial name
†Balaur bondoc
Csiki et al., 2010

Balaur is a

type specimen
).

Fossils of Balaur were found in the

ratites and insular barn owls[4] as well as the extinct moa of New Zealand[5] and the extinct dodo of Mauritius
.

Discovery and naming

Skeletal reconstruction showing known remains in white

The first small bones belonging to Balaur bondoc consisted of six elements of the front limbs. Named specimens FGGUB R. 1580–1585, these were discovered in 1997 in

Proceedings of the National Academy of Sciences.[10] The 1997 specimens indicate an individual about 45% longer than the holotype; they were also found in a younger stratum
.

The

Panaves. 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]

Description

Balaur bondoc compared in size to a human

Balaur is a

autapomorphies, including a reduced and presumably nonfunctional third finger, consisting of only one rudimentary phalanx.[10][12]

The partial skeleton was collected from the red floodplain

pectoral and pelvic girdles, and a large part of the limbs. It is the first reasonably complete and well-preserved theropod from the Late Cretaceous of Europe.[10]

Restoration
Balaur reconstructed as an avialan

It is similar in size to

metatarsals into a tarsometatarsus. The degree of fusion is typical for the Avialae, the evolutionary branch of the birds and their direct relatives.[14]

Classification

Left foot and tibia of the holotype

The position of Balaur relative to other bird-like dinosaurs and early birds has been difficult to determine. The initial

Velociraptor mongoliensis. A 2013 study by Brusatte and colleagues, using a modified version of the same data, found it in an unresolved close relationship with the dromaeosaurids Deinonychus and Adasaurus, with some possible alternative trees suggesting it branched off before the common ancestor of Deinonychus and Velociraptor, while others maintained it as the closest relative of Velociraptor, with Adasaurus as their next closest relative.[14]

More recent analyses using different sets of anatomical data have since cast doubt on a dromaeosaurid classification for Balaur. In 2013, a larger analysis containing a wide variety of coelurosaurs found that Balaur was not a dromaeosaurid at all, but a basal

Omnivoropterygiformes.[15] A study published in 2014 found Balaur to be sister to Pygostylia.[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. Many of the presumed unique traits would in fact have been normal for a member of the Avialae. Typical bird features included the degree of fusion of the limb bones, the functional first toe, the first toe claw not being smaller than the second claw, a long penultimate phalanx of the third toe, a small fourth toe claw and a long fifth metatarsal.[18]

On the other hand, some recent studies continue to place Balaur within the Velociraptorinae.[19][20]

Paleobiology

Diet and lifestyle

Reconstruction of Balaur as a dromaeosaur, using the originally-proposed kicking motion

Little is known about the behavior of Balaur. Because of the lack of skull material, it is impossible to determine by the shape of the teeth whether Balaur was a carnivore or a herbivore. The original description assumed it was carnivorous because it had been found that it was closely related to

island ecosystem, as neither the skeletons nor teeth of larger theropods have been discovered in Romania. He also believed 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.[21] 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.[12][22] 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. Once it was worn out, they might have proceeded to feast while it was still alive as some modern birds of prey still do. Due to the shape of the claws, they would not have been effective in slashing attacks.[23] The very short, fused metatarsus of Balaur and enlarged first claw, strange even by true dromaeosaur standards, are thought to be consistent with these newer studies, lending further support to the idea that Balaur was a predator.[24]

Italian paleontologist Andrea Cau has speculated that the aberrant features present in Balaur may have been a result of this theropod being omnivorous or herbivorous rather than carnivorous like most non-avian theropods. The lack of the third finger may be a sign of reduced predatory behavior, and the robust first toe could be interpreted as a weight-supporting adaptation rather than a weapon. 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. Cau referred to this as the "Dodoraptor" model.[25] However, in light of the research done by Fowler et al., Cau has remarked that the anatomy of Balaur may be more congruent with the hypothesis that Balaur was predatory after all.[26]

In 2015, Cau et al. reconsidered the ecology of Balaur again in their reevaluation of its phylogenetic position, arguing that if Balaur was an avialan, it would be phylogenetically bracketed by taxa known to have been herbivorous, such as Sapeornis and Jeholornis. This suggests a non-hypercarnivorous lifestyle to be a more parsimonious conclusion and supports Cau's initial interpretations of its specializations. 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. Balaur had a broad pelvis, a broad foot, a large first toe, and broad lower ends of the metatarsals relative to the articulation surfaces; such a combination can in the remainder of the Theropoda only be found with the herbivorous Therizinosauridae.[18]

Island syndrome

See also: Island syndrome § Hațeg Island
Pair of Balaur bondoc in their native Hațeg Island environment of what is now Romania

During the

barn owls[4] as well as the extinct moa of New Zealand[5] and the extinct dodo of Mauritius
.

In addition to island syndrome, species isolated on islands are also affected by genetic drift and the founder effect to a greater degree due to the small effective population size. This can magnify the effects of mutations which may otherwise be diluted in a larger population and may have given rise to some of the neomorphisms seen in Balaur like the retractable claw on its first toe.[10]

In 2010, the increased robustness of Balaur was compared to parallel changes seen in isolated herbivorous mammals.[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.[14] The 2015 interpretation of Balaur as an omnivorous member of the Avialae, suggested it was the descendant of a flying species that had developed a larger size similar to the development in several other island herbivores. This would then be a rare instance of secondary flightlessness in a paravian to resemble a dromaeosaurid, as predicted by Gregory S. Paul.[18]

References

  1. ^ "Definitie: balaur | DEX online". Dexonline.ro. Retrieved 2010-09-25.
  2. ^ "Definitie: bondoc | DEX online". Dexonline.ro. Retrieved 2021-03-12.
  3. doi:10.1016/j.palaeo.2010.01.026
    .
  4. ^
    S2CID 20356466
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  5. ^
    S2CID 83768608
    .
  6. ^ a b "'Stocky dragon' dinosaur terrorized Late Cretaceous Europe". Physorg.com. Archived from the original on 1 September 2010. Retrieved 2010-09-01.
  7. ^ "Scientists Unveil New and Improved Velociraptor Cousin – Time NewsFeed". Newsfeed.time.com. 2010-08-31. Retrieved 2010-09-01.
  8. ^ Csiki, Z. & Grigorescu, D. (2005). "A new theropod from Tustea: are there oviraptorosaurs in the Upper Cretaceous of Europe?" (PDF). Kaupia. 14: 78. Archived from the original (PDF) on 2016-03-04. Retrieved 2010-09-26.
  9. ^ "Balaurul bondoc zguduie lumea științei". Adevărul (in Romanian). August 2010. Archived from the original on 14 September 2010. Retrieved 2010-09-01.
  10. ^
    PMID 20805514
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  11. ^
    PMID 20805514
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  12. ^ a b c "BBC News – Beefy dino sported fearsome claws". Bbc.co.uk. 2010-08-31. Retrieved 2010-09-01.
  13. OCLC 985402380
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  14. ^
    S2CID 59932467
    .
  15. S2CID 4364892
    .
  16. S2CID 37866029
    .
  17. S2CID 4464659
    .
  18. ^
    PMID 26157616
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  19. S2CID 231597229
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  20. S2CID 243849373
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  21. ^ "New Predatory Dinosaur Discovered in Romania". Wired. 2009-01-04. Archived from the original on 2010-08-31. Retrieved 2010-09-01.
  22. ^ Caroline Davies (2010-08-30). "Frightening new predator found in the homeland of the dragon | Science". The Guardian. London. Archived from the original on 31 August 2010. Retrieved 2010-09-01.
  23. PMID 22194962
    .
  24. ^ Choi, Charles (14 December 2011). "Velociraptors' Killer Claws Helped Them Eat Prey Alive". LiveScience.
  25. ^ Cau, A (2010). Balaur: More than just a "Double-Sickle-Clawed Raptor" Theropoda, September 1, 2010.
  26. ^ Cau, A (2011). The Extinction of Dodoraptor (?) Theropoda, December 30, 2011.
  27. ^
    PMID 20435913
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  28. PMID 32315628
    .

External links

Wikimedia Commons has media related to Balaur.

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