Adasaurus
Adasaurus | |
---|---|
Reconstructed skull from the holotype | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | †Dromaeosauridae |
Clade: | †Eudromaeosauria |
Subfamily: | †Velociraptorinae |
Genus: | †Adasaurus Barsbold, 1983 |
Type species | |
†Adasaurus mongoliensis Barsbold, 1983
|
Adasaurus (
Adasaurus was a large dromaeosaurid that was about 2.39–3.5 m (7.8–11.5 ft) long weighing 36.4–87 kg (80–192 lb). Unlike other dromaeosaurids, Adasaurus developed a rather small and blunt sickle claw that likely had a reduced use, and a recurved lacrimal bone; this latter trait is also shared with Austroraptor. Though reduced, the sickle claw retained the characteristic rounded articulation of most dromaeosaurids.
Adasaurus was originally regarded as a
History of discovery
Adasaurus was first figured in
Adasaurus is known from the
Description
Adasaurus was a rather large-sized dromaeosaurid. The holotype has an estimated length of 2.39 m (7.8 ft) with a weight of 36.5 kg (80 lb).
Skull
On the right side of the
Skeleton
The
The posterior top border of the ilium is proportionally more thickened than that of Achillobator,[13] and the anterior border of the anterior blade of the ilium has a similar shape to that of Saurornitholestes. This anterior border has a notched appearance that is characteristic to Adasaurus. As a whole, the top border is straightened in shape. The pubic peduncle—a robust anterior extension that articulates with the pubis—is wide and developed to the bottom. A large supratrochanteric (above the trochanter of the femur) extension is absent on the ilium. Like other dromaeosaurids, the pubis is elongated with an expanded pubic boot (lower end) and features an opisthopubic (backwards directed) condition.[4] The digit II ungual is not hypertrophied (elongated) as in most dromaeosaurids,[14][4] and though Adasaurus features a similar metatarsal II-III ratio to that of Balaur, this is due to the reduced sickle claw of digit II instead of an elongated ungual of digit I. Metatarsal III of the paratype shows that a tubercle is present on the extensor surface and this tuberosity likely originates the insertion of the muscle tibialis cranialis.[5] The lower tarsals and upper ends of the metatarsals are somewhat fused.[7][4]
Classification
Adasaurus is a member of
Below is a cladogram based on the phylogenetic analysis conducted by James G. Napoli and colleagues in 2021:[21]
Velociraptorinae |
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Paleobiology
Paleopathology
In 1997, Norell and Makovicky stated that the holotype specimen of Adasaurus represents a largely pathologic (due to injury or disease) individual.[14] They reaffirmed this observation in 2004 by claiming the pelvis as pathological.[22] However, during the large revision of the Dromaeosauridae by Turner and colleagues in 2012, the holotype was re-examined and found to be non-pathological. Instead of reflect injured elements, several surfaces may represent the advanced age of the individual, such as the fused upper ends of the metatarsus.[4]
Sickle claw function
Kubota and Barsbold in 2006 stated that the highly reduced sickle claw of Adasaurus may have been used with less frequency than other
In 2011, Denver Fowler and colleagues suggested a new method by which dromaeosaurids may have taken smaller prey. This predation model, "Raptor Prey Restraint" (RPR), proposes that dromaeosaurids killed their prey by leaping onto their quarry, pinning it under their body weight, and gripping it tightly with the large, sickle claws of the pedal digit II—in a manner very similar to extant accipitrid birds of prey. Like accipitrids, the dromaeosaurid would then begin to feed on the animal while still alive, until it eventually died from blood loss and organ failure. This proposal is based primarily on comparisons between the morphology and proportions of the feet and legs of dromaeosaurids to several groups of extant birds of prey with fairly known predatory behaviors. Fowler and colleagues found that the feet and legs of dromaeosaurids most closely resemble those of eagles and hawks, especially in terms of having an enlarged second claw and a similar range of grasping motion, but the short metatarsus and foot strength would have been more similar to that of owls. The RPR model would be consistent with other aspects of dromaeosaurid anatomy, such as their unusual dentition and arm morphology. The arms were covered in long feathers and may have been used as flapping stabilizers for balance while atop a struggling prey, along with the stiff counter-balancing tail. Lastly, the comparatively weak jaws would have been useful for eating prey alive but not as useful for forceful dispatch of the prey.[23]
In 2019, Peter Bishop reconstructed the leg skeleton and musculature of Deinonychus by using three-dimensional models of muscles, tendons, and bones. With the addition of mathematical models and equations, Bishop simulated the conditions that would provide maximum force at the tip of the sickle claw and therefore the most likely function. Among the proposed modes of the sickle claw use are: kicking to cut, slash or disembowel prey; for gripping onto the flanks of prey; piercing aided by body weight; to attack vital areas of the prey; to restrain prey; intra- or interspecific competition; and digging out prey from hideouts. The results obtained by Bishop showed that a crouching posture increased the claw forces, however, these forces remained relatively weak indicating that the claws were not strong enough to be used in slashing strikes. Rather than being used for slashing, the sickle claws were more likely to be useful in flexed leg angles such as restraining prey and stabbing prey at close quarters. These results are consistent with the Fighting Dinosaurs specimen, which preserves a Velociraptor and Protoceratops locked in combat, with the former gripping onto the other with its claws in a non-extended leg posture. Despite the obtained results, Bishop considered that the capabilities of the sickle claw could have varied within taxa given that among dromaeosaurids, Adasaurus had an unusually smaller sickle claw that retained the characteristic ginglymoid—a structure divided in two parts—and hyperextensible articular surface of the penultimate phalange. He could neither confirm nor disregard that the pedal digit II could have loss or retain its functionally.[6]
Paleoenvironment
Adasaurus is known from the
See also
References
- ^ a b c d Barsbold, R. (1983). "Хищные динозавры мела Монголии" [Carnivorous dinosaurs from the Cretaceous of Mongolia] (PDF). Transactions of the Joint Soviet-Mongolian Paleontological Expedition (in Russian). 19: 89. Translated paper
- ^ Barsbold, R. (1977). "Эволюции Хищных Динозавров" [The Evolution of Predatory Dinosaurs]. Transactions of the Joint Soviet-Mongolian Paleontological Expedition (in Russian). 4: 48−56. Translated paper
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