Velociraptor
Velociraptor is a dinosaur genus, belonging to the dromaeosaurid lineage of theropods. It lived during the Late Cretaceous, approximately 75-71 million years ago, in Central Asia. This bipedal carnivore was relatively small compared to other dromaeosaurids, and its body was covered by feathers. It had a long tail and an enlarged curved claw on each of its hindfoots, which could be used to tackle down its prey and tear its skin and soft tissues. However, it differed from other dromaeosaurids by having a long and low skull, with an up-turned snout.
Velociraptor, commonly often referred as "raptor", is one of the most popular and best known dinosaurs by the greater public. Furthermore, Velociraptor have over a dozen described fossil skeletons, which is the most numerous fossil material amongst all dromaeosaurid dinosaurs.
Velociraptor mongoliensis. By Fred Wierum - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=63257512
Known occurrences of Velociraptor fossils.
Discovery
The very first fossil specimen of Velociraptor was discovered during an expedition of the American Museum of Natural History by Peter Kaisen in the Gobi Desert, Mongolia, in 1923. These remains included a complete skull and one of the raptorial claws. Then, in 1924, Henry Fairfield Osborn described the new dinosaur genus Velociraptor based on these fossils - however, he assumed that the claw belonged to one of the forelimbs[1]. The name came from the Latin words velox (meaning 'swift') and raptor (meaning 'robber' or 'plunderer'), and the type species of the new genus was named as Velociraptor mongoliensis[1].
In the second half of the 20th century, Soviet, Polish and Mongolian researchers in cooperation, discovered several further fossils of Velociraptor in the Gobi Desert. The most important of these, discovered by a Polish-Mongolian team, was the "Fighting Dinosaurs" specimen, which preserved a Velociraptor and a Protoceratops during fighting against each other[2]. Between 1980 and 1988 further Velociraptor fossils were discovered by a Chinese-Canadian research team in Chinese Inner Mongolia[3]. After 1990, a joint Mongolian-American expedition revealed several new Velociraptor skeletons in the Gobi Desert[4]. A new species, V. osmolskae was described by a Chinese-Belgian expedition from Chinese Inner Mongolia in 2008[5].
Velociraptor mongoliensis, type skull. By Smokeybjb - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20754386
Fighting dinosaurs: Velociraptor versus Protoceratops. By Yuya Tamai from Gifu, Japan - 2014-03-25 13.04.56, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=31836685
Taxonomy
Osborn originally placed Velociraptor in the family Megalosauridae when he described the genus. However, Velociraptor is considered now belonging to a derived clade of the family Dromaeosauridae, which is called Eudromaeosauria. Currently two valid species belongs to the genus, both found in the Gobi Desert: V. mongoliensis from Mongolia, and V. osmolskae from Chinese Inner Mongolia[6].
Description and anatomy
Velociraptor was a bipedal dinosaur. Adult specimens could reach the length of 2 meters, and could be as high as 0.5 meters at the hip, weighing up to 15-20 kg[7][8]. The skull was about 25 cm long, and had an upturned snout which was unique between dromaeosaurids. Velociraptor had 26-28 widely spaced and serrated teeth on both sides of each jaws. It had a relatively large hand with three fingers, each bearing a strongly curved claw. From these, the second digit was the longest, and the first one the shortest. Due to the structure of wirst bones, the hands were held facing inward with their palm surface, and not downward, as in many old illustrations[6].
Velociraptor, just like other dromaeosaurids, walked on its third and fourth digits. Its first digit on the foot was a small dewclaw, and the second was highly modified, normally held rertracted off the ground, having an enlarged, sickle-shaped claw, which could reach even 6.5 cm around its outer edge. Velociraptor had a long tail, with long bony projections on the upper part of each vertebrae, and ossified tendons at the ventral side. Originally these structures were assumed to stiffen the long tail, however, at least one newly found specimen with intact tail vertebrae was fossilized with its tail curved sideways into an S-shape, which allows us to suppose that the tail had much greater horizontal flexibility than it was thought before[9].
Microraptor gui, a dromaeosaurid dinosaur that lived much earlier than Velociraptor, discovered in 2003, had a feathered body and four feathered wings[10]. Later in 2007, quill knobs were found on the forearm of a Velociraptor[11], which means that Velociraptor also had feathers. Though the ancestors of Velociraptor probably could fly, Velociraptor itself, along with larger dromaeosaurids, became secondarily flightless. Just like today's flightless birds, these dinosaurs also kept their feathers.
Velociraptor mongoliensis. By Jordan Mallon - PaleoPortfolio, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=1027194
Paleobiology
According to our present knowledge, Velociraptor was warm-blooded, at least to some degree[8]. As there was found a fossilized Velociraptor and a Protoceratops fighting against each other ("fighting dinosaurs specimen"), we have direct evidence of the predatory behaviour in case of Velociraptor. It is considered that they were rapidly buried in a sandstorm[12]. Inferred from its scleral rings, Velociraptor might have been a nocturnal animal[13].
The distinctive claw of dromaeosaurids originally was thought to be a slashing weapon, which was used to cut into and disembowel the prey[14]. However, as the inner edge of the claw was not sharp but rounded, now it is regarded that the claw was rather used to pierce vital organs, for example veins and arteries of the throat or the trachea[12]. All Velociraptor fossils were found soilitarily, which means that there is no direct evidence for the pack hunting behaviour of this dinosaurs. However, the related Deinonychus has fossil evidence for cooperative hunting[15], and in China there was a fossil trackway found which shows that six dromaeosaurid specimens moved together like a pack[16].
In 2011 a new theory was suggested by Denver Fowler and his colleagues, with a method called "raptor prey restraint" (RPR) describing the preying behaviour of dromaeosaurids like Velociraptor. Based on on comparisons between the leg and feet morphology and proportions of dromaeosaurs and several groups of todays birds with known predatory behaviors, RPR suggests that Velociraptor first jumped onto its prey and pinned it under its body weight, then gripped it tightly with the large curved claws. It also means that Velociraptor could began to feed on the prey while it was still alive. During the attack, the feathered arms and tile could help Velociraptor to maintain its balance on the wriggling prey[17]. A research based on the endocranium of Velociraptor suggest that the animal could sense a wide range of sound frequencies (2,368-3,965 Hz) which helped it to track down the prey[18].
Scientific references
[1] Osborn, H.F. (1924): Three new Theropoda, Protoceratops zone, central Mongolia. American Museum Novitates, (144): 1-12.
[2] Kielan-Jaworowska, Z.; Barsbold, R. (1972): Narrative of the Polish-Mongolian Paleontological Expeditions. Paleontologica Polonica, 27: 5-13.
[3] Jerzykiewicz, T.; Currie, P.J.; Eberth, D.A.; Johnston, P.A.; Koster, E.H.; Zheng, J.J. (1993): Djadokhta Formation correlative strata in Chinese Inner Mongolia: an overview of the stratigraphy, sedimentary geology, and paleontology and comparisons with the type locality in the pre-Altai Gobi. Canadian Journal of Earth Sciences, 30 (10): 2180-2195. doi: 10.1139/e93-190.
[4] Norell, M.A.; Makovicky, P.J. (1997): Important features of the dromaeosaur skeleton: information from a new specimen. American Museum Novitates, (3215): 1-28.
[5] Godefroit, P.; Currie, P.J.; Li, H.; Shang, C.Y.; Dong, Z. (2008): A new species of Velociraptor (Dinosauria: Dromaeosauridae) from the Upper Cretaceous of northern China. Journal of Vertebrate Paleontology. 28 (2): 432-438. doi: 10.1671/0272-4634(2008)28[432:ANSOVD]2.0.CO;2.
[6] Paul, G.S. (2002): Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. Baltimore: Johns Hopkins University Press. ISBN 978-0-8018-6763-7.
[7] Paul, G.S. (1988): Predatory Dinosaurs of the World. New York: Simon & Schuster. pp. 464. ISBN 978-0-671-61946-6.
[8] Campione, N.E.; Evans, D.C.; Brown, C.M.; Carrano, M.T. (2014): Body mass estimation in non-avian bipeds using a theoretical conversion to quadruped stylopodial proportions. Methods in Ecology and Evolution, 5 (9): 913-923. doi: 10.1111/2041-210X.12226.
[9] Norell, M.A.; Makovicky, P.J. (1999): Important features of the dromaeosaurid skeleton II: information from newly collected specimens of Velociraptor mongoliensis. American Museum Novitates, (3282): 1-45.
[10] Xu, X.; Zhou, Z.; Wang, X.; Kuang, X.; Zhang, F.; Du, X. (2003): Four-winged dinosaurs from China. Nature, 421 (6921): 335-340. doi: 10.1038/nature01342.
[11] Turner, A.H.; Makovicky, P.J.; Norell, M.A. (2007): Feather quill knobs in the dinosaur Velociraptor. Science, 317 (5845): 1721. doi: 10.1126/science.1145076.
[12] Carpenter, K. (1998): Evidence of predatory behavior by theropod dinosaurs. Gaia, 15: 135-144.
[13] Schmitz, L.; Motani, R. (2011): Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology. Science, 332(6030): 705-8.
[14] Ostrom, J.H. (1969): Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Bulletin of the Peabody Museum of Natural History, 30: 1-165. doi: 10.2307/j.ctvqc6gzx.
[15] Maxwell, W.D.; Ostrom, J.H. (1995): Taphonomy and paleobiological implications of Tenontosaurus-Deinonychus associations. Journal of Vertebrate Paleontology 15 (4): 707-712. doi: 10.1080/02724634.1995.10011256.
[16] Li, R.; Lockley, M.G.; Makovicky, P.J.; Matsukawa, M.; Norell, M.A.; Harris, J.D.; Liu, M. (2007): Behavioral and faunal implications of Early Cretaceous deinonychosaur trackways from China. Die Naturwissenschaften, 95 (3): 185-191. doi: 10.1007/s00114-007-0310-7.
[17] Fowler, D.W.; Freedman, E.A.; Scannella, J.B.; Kambic, R.E. (2011): The Predatory Ecology of Deinonychus and the Origin of Flapping in Birds. PLOS ONE. 6 (12): e28964. doi: 10.1371/journal.pone.0028964.
[18] King, J. L.; Sipla, J.S.; Georgi, J.A.; Balanoff, A.M.; Neenan, J.M. (2020): The endocranium and trophic ecology of Velociraptor mongoliensis. Journal of Anatomy, 237 (5): 861-869. doi: 10.1111/joa.13253.