In 1922Matthew and Brown named the new genus and species Dromaeosaurus albertensis, considering it a new type within the family Deinodontidae, a now-defunct family name that once applied to the tyrannosaurs. Not long after, Velociraptor was discovered in Mongolia by the Central Asiatic Expedition. Dromaeosaur research was fairly quiet until the 1960s, when John Ostrom described the new genus and species Deinonychus antirrhopus.[2] This discovery played a major role in setting off the Dinosaur Renaissance because Deinonychus was obviously a vigorous, active animal, and exhibited characteristics linking it to the origin of birds. As such it brought support for controversial reinterpretations of dinosaurs as warm-blooded and ancestral to birds.[3] Its distinct nature and similarity to Dromaeosaurus led Ostrom to follow Edwin Colbert and Dale Russel's suggestion that the Dromaeosaurinae be regarded as its own family separate from the Deinodontidae.[4]
After Ostrom's initial research on Deinonychus, evidence continued to mount for a close evolutionary relationship between dromaeosaurids and birds.[5] The dromaeosaurid Sinornithosaurus milennii, described in 1999 by Xu, Wang, and Wu, is a notable example as the fine-grained Chinese limestone from which it was collected preserved its life covering of feathers.[2] Discoveries of feathered dromaeosaurids continued into the 2000s. Xu, Zhou, and Wang named the new genus Microraptor in 2000.[6] Three years later, Xu and others would report a new species in this genus that exhibited a bizarre "four winged" body plan with long pennaceous flight feathers on both its front and hind limbs.[7]
The Crow people and other Native American groups inhabiting Montana used to use rocks from the Cloverly Formation to make red pigments. Since the red pigments are richest in the same layers of the formation that preserve dinosaur fossils, it is likely that Native Americans encountered Deinonychus fossils long before scientifically trained paleontologists.[1]
John Ostrom described the new genus and species Deinonychus antirrhopus.[6] This description provided the scientific literature with its first detailed information about the anatomy of the dromaeosaurid body, as previous work focused on the skull.[2] He proposed that Deinonychus killed its prey with the enlarged, sharply curved claws on the second toe of its feet.[9]
Ostrom further described the anatomy of Deinonychus antirrhopus, providing further details about the anatomy of its body.[2] Ostrom proposed that Deinonychus only walked on two of its toes.[9]
Barsbold described the new genus and species Adasaurus mongoliensis.[6] Unlike most dromaeosaurs, famous for the "killing claws" on their second toe, the second toe claw of A. mongoliensis was relatively small and not sharply curved. It is similar to those of troodontids.[9]
Osmolska challenged Kielan-Jaworowska and Barsbold's 1972 interpretation of an associated skeleton of Velociraptor and Protoceratops as being of two animals killed and preserved while locked in mortal combat. She reinterpreted the association as a Velociraptor that had been killed while scavenging an already dead Protoceratops.[9]
Ostrom speculated that Deinonychus hunted in packs to subdue prey larger than itself based on an association between several Deinonychus skeletons and a specimen of the ornithopodTenontosaurus.[9]
Currie followed Barsbold's division of Dromaeosauridae into Dromaeosaurinae and Velociraptorinae. However, he proposed differing definitions for these subfamilies and argued that they had different members than were included under Barsbold's classification scheme.[5]
Maxwell and Ostrom reported on the association of Deinonychus teeth and Tenontosaurus remains and argued that these provided further support for the hypothesis that Deinonychus was a pack hunter.[9]
Unwin and others followed the fighting-to-the-death interpretation of the fighting dinosaurs specimen.[9]
Chatterjee argued that dromaeosaurids lived in trees based on the anatomy of their hands and the backward orientation of the pubic bones in their pelvis.[9]
Reid examined histological sections of the bones of Saurornitholestes to see whether or not they were consistent with the idea that dromaeosaurids were warm blooded. However, the results of his study were inconclusive.[9]
Ruben and others attempted to reconstruct the way air would flow through the snouts of dromaeosaurids during respiration to see whether or not it was consistent with the airflow patterns of modern cold or warm-blooded animals. They found that the probable course of airflow through the snout of a living, breathing dromaeosaurid would have been more consistent with that of a cold blooded animal. However, the anatomical reconstructions the researchers used to draw these conclusions have been criticized for positioning the choana too far forward and for excluding the animals' secondary palate.[9]
D. L. Brinkman and others reinterpreted the association between several Deinonychus specimens and a Tenontosaurus as preserving the aftermath of an ancient feeding frenzy rather than as evidence of pack hunting behavior in Deinonychus as argued by Ostrom.[9]
Clark and others argued that it was impossible to know whether or not Velociraptor was a predator of Protoceratops based on the famous "fighting dinosaurs" specimen, since this was only one specimen.[9]
Xu, Wang, and Wu described the new genus and species Sinornithosaurus millenii.[6] The specimen actually preserved the remains of the feathers that covered the animal in life. The presence of a feathery covering is consistent with the idea that dromaeosaurids were warm-blooded.[9] They also performed a cladistic analysis of the Dromaeosauridae, finding more support for dividing the family into Dromaeosaurinae and Velociraptorinae. The researchers found both groups to be monophyletic clades, with Sinornithosaurus milenii the sister group to both, and therefore the most primitive known dromaeosaurid.[10]
A. R. Jacobsen published a description of a dentary referred to Saurornitholestes with tooth marks.[11] The specimen was preserved in the Dinosaur Park Formation.[12] Although a specific identification cannot be made, the shape of the preserved serration marks implicate a juvenile individual of one of the formation's tyrannosaurids, like Gorgosaurus, Daspletosaurus, or Aublysodon.[13] All of the marks on the jawbone seem to have been left by the same animal because the serration marks all share the same morphology.[14]
Kevin Padian, Ji Qiang and Ji Shu-an published a review of known feathered dinosaurs and their implications for the origin of flight.[15] The authors observed that many aspects of the distribution of feather homologues in the dinosaur family tree met the expectations of earlier phylogenetic hypotheses, including a gradual transition from primitive filaments in Sinosauropteryx to the shared filaments and "rudimentary" true feathers in Caudipteryx and Protarchaeopteryx, to flight feathers in Archaeopteryx.[16] However, they also noted, only filamentous protofeathers had been observed in dromaeosaurs like Sinornithosaurus, when Caudipteryx-style true feathers would be expected due to the family's phylogenetic position.[17] Also noted were the lack of known integumentary structures among troodontids.[17] The authors proposed that either science's understanding of coelurosaur evolution is faulty or feathers evolved multiple times.[17]
Cladogram of feathered dinosaurs from Padian et al. 2001
^I. Yu. Bolotskii; Yu. L. Bolotskii; A. P. Sorokin (2019). "The first find of an ungual phalanx of a dromaeosaurid dinosaur (Dinosauria: Dromaeosauridae) from the Blagoveshchensk area of Late Cretaceous dinosaurs (Amur Region, Russia)". Doklady Earth Sciences. 484 (1): 18–20. Bibcode:2019DokES.484...18B. doi:10.1134/S1028334X19010100. S2CID134803475.
Phil R. Bell & Philip J. Currie (2015). "A high-latitude dromaeosaurid, Boreonykus certekorum, gen. et sp. nov. (Theropoda), from the upper Campanian Wapiti Formation, west-central Alberta". Journal of Vertebrate Paleontology. 36: e1034359. doi:10.1080/02724634.2015.1034359. S2CID131680329.
Christiansen P. & Bonde N. (2003). "The first dinosaur from Denmark". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 227 (2): 287–299. doi:10.1127/njgpa/227/2003/287.
Czerkas, S. A.; Zhang, D.; Li, J; Li, Y (2002). "Flying dromaeosaurs". In Czerkas, S. J. (ed.). Feathered Dinosaurs and the Origin of Flight. Vol. 1. Blanding: The Dinosaur Museum. pp. 96–126.
Gong; Martin; Burnham; Falk; Hou (2012). "A new species of Microraptor from the Jehol Biota of northeastern China". Palaeoworld. 21 (2): 81–91. doi:10.1016/j.palwor.2012.05.003.
Horner, John R. (2001). Dinosaurs Under the Big Sky. Mountain Press Publishing Company. ISBN0-87842-445-8.
Horner, John R.; Weishampel, David B.; Forster, Catherine A. (2004). "Hadrosauridae". In Weishampel, D. B.; Dodson, P.; Osmolska, H. (eds.). The Dinosauria (2 ed.). Berkeley: University of California Press. pp. 438–463. ISBN978-0-520-25408-4.
Jacobsen, A. R. (2001). "Tooth-marked small theropod bone: An extremely rare trace". In Tanke, D. H.; Carpenter, K. (eds.). Mesozoic Vertebrate Life. Life of the Past. Indiana University Press. pp. 58–63.
Lü, J.-C.; Xu, L.; Zhang, X.-L.; Ji, Q.; Jia, S.-H.; Hu, W.-Y.; Zhang, J.-M.; Wu, Y.-H. (2007). "New dromaeosaurid dinosaur from the Late Cretaceous Qiupa Formation of Luanchuan area, western Henan, China". Geological Bulletin of China. 26 (7): 777–786.
Makovicky, Peter J.; Norell, Mark A. (2004). "Troodontidae". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 184–195. ISBN0-520-24209-2.
Mayor, Adrienne (2005). Fossil Legends of the First Americans. Princeton University Press. ISBN0-691-11345-9.
Norell, M.A. & Makovicky, P.J. (2004). "Dromaeosauridae". In Weishampel, D.B.; Dodson, P. & Osmólska, H. (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 196–210. ISBN0-520-24209-2.
Ostrom, John H. (1969). "Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana". Peabody Museum of Natural History Bulletin. 30: 1–165.
Padian, K.; Ji, Qiang; Ji, Shu-An (2001). "Feathered dinosaurs and origin of flight". In Tanke, D. H.; Carpenter, K. (eds.). Mesozoic Vertebrate Life. Life of the Past. Indiana University Press. pp. 117–135.
Xu, X.; Wang, X.-L. (2004). "A New Dromaeosaur (Dinosauria: Theropoda) from the Early Cretaceous Yixian Formation of Western Liaoning". Vertebrata PalAsiatica. 42 (2): 11–119.
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