Ornitholestes
Ornitholestes | |
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Skeleton mount, Royal Tyrrell Museum
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Clade: | Tyrannoraptora
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Clade: | Maniraptoromorpha
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Genus: | †Ornitholestes Osborn, 1903 |
Type species | |
†Ornitholestes hermanni Osborn, 1903
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Ornitholestes (meaning "bird robber") is a small
To date, Ornitholestes is known only from a single partial skeleton with a badly crushed skull found at the Bone Cabin Quarry near Medicine Bow, Wyoming, in 1900. It was described by Henry Fairfield Osborn in 1903. An incomplete hand was later attributed to Ornitholestes, although it now appears to belong to Tanycolagreus. The type (and only known) species is O. hermanni. The specific name honors the American Museum of Natural History preparator Adam Hermann.
Discovery and naming
Ornitholestes was the first theropod to be discovered in the 1900s.[2] The holotype skeleton (AMNH 619) was excavated in July 1900 in the Bone Cabin Quarry in Wyoming by an American Museum of Natural History expedition by Peter C. Kaisen, Paul Miller and Frederic Brewster Loomis.[3][4] It represents a partial skeleton with skull, including numerous elements of the vertebral column, the forelimbs, pelvis and hindlimbs. Henry Fairfield Osborn named and scientifically described the specimen in 1903.[5] The genus name Ornitholestes, initially suggested by Theodore Gill, means "bird robber" and is derived from the Greek ὄρνις/ornis, ornithos ("bird") and λῃστήσ/lestes ("robber").[6][7] The species name (O. hermanni) honors Adam Hermann, the head preparator at the Museum, who directed the restoration and mounting of the skeleton.[3]
An incomplete hand (AMNH 587) was assigned to Ornitholestes by Osborn in his 1903 description of the genus.[8] However, as Gregory S. Paul (1988) noted, the poor preservation of the corresponding elements in the type specimen made this association "tentative."[9] In 2005, Kenneth Carpenter et al. described a new small theropod, Tanycolagreus, whose skeleton was found in Bone Cabin Quarry only a few hundred yards from AMNH 587.[10] Since AMNH 587 was virtually identical to the preserved hand of the Tanycolagreus type specimen, it is now considered to belong to that dinosaur and not to Ornitholestes.[11] Following this reassignment, Phil Senter (2006) noted that "our knowledge of Ornitholestes can be drawn now only from the holotype."[12] John Foster (2007) reported that some fragments from Dry Mesa Quarry may belong to Ornitholestes,[13] though these have not yet been described.
In 1920
Description
In his 1903 description, Osborn wrote that the length of Ornitholestes along "the skull and vertebral column as restored" was 2.22 m (7.28 ft).[3] However, this reconstruction was inaccurate, being based in part on Othniel Charles Marsh's restoration of the basal sauropodomorph Anchisaurus, and the neck and trunk were both too elongated.[17] David Norman (1985) and John Foster (2007) both estimated that Ornitholestes was about 2 m (6.6 ft) long.[18] Gregory S. Paul's 1988 Predatory Dinosaurs of the World listed the length of Ornitholestes as approximately 2.08 m (6.82 ft).[19] Paul (1988) and Foster (2007) both estimated that Ornitholestes weighed 12.6 kg (27.8 lb).[20] John A. Long and Peter Schouten (2008) suggested a slightly higher figure, 15 kg (33 lb).[21]
Ornitholestes was a bipedal carnivore.
The front teeth of Ornitholestes were somewhat conical, with reduced serrations; the back teeth were recurved and more sharply serrated, similar to those of other theropod dinosaurs.
An area of broken bone near the external naris (nostril) appears to bulge upward, which led Gregory S. Paul to suggest in Predatory Dinosaurs of the World (1988) that Ornitholestes had a nasal horn "rather like a chicken's comb in looks."[33] Both Oliver W.M. Rauhut (2003) and Kenneth Carpenter et al. (2005a) rejected that interpretation, and indicated that the upward flare of bone was due to post-mortem crushing of the skull.[34] Paul's updated illustration of Ornitholestes in his 2010 Princeton Field Guide to Dinosaurs no longer contains the nasal horn.[35]
Ornitholestes had a relatively short neck with a slight sigmoidal (S-shaped) curve.[36] The tail was long and whiplike, comprising over half of the body's length.[37] Not all of the vertebrae were preserved, but Osborn (1917) estimated that Ornitholestes had nine or ten cervical (neck) vertebrae, thirteen dorsal (back) vertebrae, four sacral (hip) vertebrae, and 39 to 44 caudal (tail) vertebrae.[38] Carpenter et al. (2005a) recorded that the specimen contained five sacral vertebrae.[39] Ornitholestes was a short-bodied theropod, and this was reflected in the short front-to-back dimensions of the cervical and dorsal vertebrae.[40]
The forelimbs of Ornitholestes were relatively long, slightly under two-thirds the length of the hind legs.[41] The humerus (upper arm bone) was heavily built, and somewhat longer than the radius and ulna (forearm bones).[42] Both the humerus and radius were straight-shafted.[43] The claws on digits I and II of the hand were about the same size.[44] Although the hand's third ungual (claw bone) was not preserved, extrapolation from the closest relatives of Ornitholestes indicates that it was probably shorter than the first two.[44]
Ornitholestes is often portrayed as a fast, long-legged theropod, but its lower limb bones were fairly short.
Classification
The
The following family tree illustrates a synthesis of the relationships of the major coelurosaurian groups based on various studies conducted in the 2010s.[57]
Coelurosauria |
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Paleobiology
In a 2001 study conducted by Bruce Rothschild and other paleontologists, 20 foot bones referred to Ornitholestes were examined for signs of stress fracture, but none were found.[58]
Forelimb function
A biomechanical study conducted by Phil Senter (2006) used articulated casts of the Ornitholestes type specimen's right forelimb to determine its range of motion.
Even when fully
When Ornitholestes bent its elbows, this would cause the forearms to move inward, towards its midline.[62] It may have used that ability to grasp prey with both hands simultaneously.[63]
Diet
Henry Fairfield Osborn, in his 1903 description of Ornitholestes, noted its large and conical front teeth, the "rapid grasping power" of its hand, and the "balancing power" of its tail; these he interpreted as adaptations to prey on contemporary birds.[3] Osborn later repudiated this hypothesis, suggesting in 1917 that Ornitholestes presented the early stages of a transition from a carnivorous to a more herbivorous lifestyle, but not before Charles R. Knight had drawn an influential and widely published illustration of Ornitholestes chasing Archaeopteryx.[64] Knight's illustration, and others derived from it, continued to appear in dinosaur books aimed at a popular audience throughout the 20th century.[52]
David Norman (1985) conceded it was "just possible, though not very likely" that Ornitholestes might have caught and eaten primitive birds.
In 2007, John Foster, a specialist on the Morrison Formation, suggested the possibility of
Paul (1988) estimated that a 12 kg (26 lb) endothermic Ornitholestes would have a daily dietary requirement of about 700 g (1.54 lb) of flesh.[71]
Feathers
Ornithologist Percy Lowe hypothesized in 1944 that Ornitholestes might have borne feathers.[72] However, this interpretation was largely disregarded for over half a century; most reconstructions of theropod dinosaurs, including Ornitholestes, portrayed them with reptile-like scaly skin. One of the few exceptions to this was Gregory S. Paul's Predatory Dinosaurs of the World (1988).[73] Robert T. Bakker's The Dinosaur Heresies (1986) accurately predicted the presence of feathers on dromaeosaurids and contended that all dinosaurs were endothermic, yet did not incorporate feathers in its illustration of Ornitholestes.[74]
In 1996, the primitive coelurosaur
References
- ^ Turner, C.E. and Peterson, F., (1999). "Biostratigraphy of dinosaurs in the Upper Jurassic Morrison Formation of the Western Interior, U.S.A." Pp. 77–114 in Gillette, D.D. (ed.), Vertebrate Paleontology in Utah. Utah Geological Survey Miscellaneous Publication 99-1.
- ^ Fastovsky and Weishampel (2005), p. 291
- ^ a b c d Osborn (1903), p. 459
- ISBN 978-0-226-07472-6
- ^ Osborn (1903), p. 459–464
- ^ Osborn (1903), p. 459; Osborn (1917), p. 733
- ^ Colbert, Edwin H. (Edwin Harris); Knight, Charles Robert (1951). The dinosaur book: the ruling reptiles and their relatives. New York: McGraw-Hill. p. 152.
- ^ Osborn (1903), p. 459; Osborn (1917), p. 736
- ^ Paul (1988b), p. 3
- ^ Carpenter et al. (2005b), p. 23, 39
- ^ Carpenter et al. (2005b), p. 39
- ^ Senter (2006), p. 1029
- ^ Foster (2007), p. 78, 179
- ^ Gilmore, C.W., 1920, "Osteology of the carnivorous Dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) and Ceratosaurus", Bulletin U.S. National Museum CX: 1-154
- ^ Hay, O.P., 1930, Second Bibliography and Catalogue of the Fossil Vertebrata of North America. Carnegie Institution of Washington. 390(II): 1-1074
- ^ Ostrom (1980)
- ^ Osborn (1917), p. 735; Paul (1988b), p. 3
- ^ Norman (1985), p. 39; Foster (2007), p. 178
- ^ Paul (1988a), p. 305
- ^ Paul (1988a), p. 305; Foster (2007), p. 178
- ^ Long and Schouten (2008), p. 73
- ^ Lambert (1993), p. 79
- ^ Paul (1988a), p. 306; Norman (1985), p. 42; Norman (1990), p. 293
- ^ Osborn (1903), p. 460; Chure (1998), p. 238
- ^ a b Paul (1988b), p. 6
- ^ Paul (1988b), p. 3; Norman (1990), p. 293
- ^ Osborn (1903), p. 460; Osborn (1917), p. 734
- ^ Paul (1988b), p. 4; Norman (1990), p. 293
- ^ Osborn (1903), p. 460
- ^ Paul (1988b), p. 3; Norman (1990), p. 292
- ^ Cristiano dal Sasso & Simone Maganuco, 2011, Scipionyx samniticus (Theropoda: Compsognathidae) from the Lower Cretaceous of Italy — Osteology, ontogenetic assessment, phylogeny, soft tissue anatomy, taphonomy and palaeobiology, Memorie della Società Italiana de Scienze Naturali e del Museo Civico di Storia Naturale di Milano XXXVII(I): 1-281
- ^ Osborn (1903), p. 460; Norman (1990), p. 293
- ^ a b Paul (1988a), p. 303
- ^ Rauhut (2003), p. 27; Carpenter et al. (2005a), p. 53
- ^ Paul (2010), p. 123
- ^ Carpenter et al. (2005a), pp. 49, 54
- ^ Osborn (1917), p. 734; Lambert (1993), p. 78
- ^ Osborn (1917), p. 735–736
- ^ Carpenter et al. (2005a), p. 58
- ^ Carpenter et al. (2005a), p. 49, 69
- ^ Ostrom (1969), p. 146; Paul (2002), p. 236
- ^ Osborn (1917), p. 738; Carpenter et al. (2005b), p. 45
- ^ Carpenter et al. (2005a), p. 60, 62
- ^ a b c Senter (2006), p. 1030
- ^ Paul (1988a), p. 306
- ^ Osborn (1917), p. 737
- ^ Carpenter et al. (2005a), p. 67
- ^ Osborn (1903), p. 463
- ^ Ostrom (1969), p. 161
- ^ Ostrom (1969), p. 161; Paul (1988b), p. 6
- ^ Paul (1988a), p. 188–189; Norman (1990), p. 280
- ^ a b Glut (1997), p. 645
- ^ Holtz et al. (2004), p. 71
- ^ Paul (1988a), p. 302; Paul (1988b), p. 3, 6
- ^ Paul (2010), p. 124
- S2CID 4364892.
- ^ Hendrickx, C., Hartman, S.A., & Mateus, O. (2015). An Overview of Non- Avian Theropod Discoveries and Classification. PalArch’s Journal of Vertebrate Palaeontology, 12(1): 1-73.
- ^ Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331-336.
- ^ Senter (2006), p. 1029–1030
- ^ a b c Senter (2006), p. 1030–1031
- ^ Senter (2006), p. 1032
- ^ Senter (2006), p. 1030–1032
- ^ Senter (2006), p. 1031
- ^ Osborn (1917), p. 733–734; Glut (1997), p. 645
- ^ Norman (1985), p. 39
- ^ Norman (1985), p. 39; Paul (1988), p. 306; Foster (2007), p. 179; Long and Schouten (2008), p. 73
- ^ Norman (1985), p. 42
- ^ Lambert (1993), p. 78
- ^ a b Foster (2007), p. 180
- ^ Foster (2007), p. 180–181
- ^ Paul (1988a), p. 404
- ^ Witmer (1992), p. 444
- ^ Paul (1988a), p. 122–123, 211
- ^ Bakker (1986), p. 99, 310
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{{cite book}}
: CS1 maint: multiple names: authors list (link - Fastovsky, David E.; Weishampel, David B. (2005). "Theropoda I: Nature red in tooth and claw". The Evolution and Extinction of the Dinosaurs. Cambridge University Press. pp. 265–299. ISBN 978-0-521-81172-9.
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- Foster, John (2007). "Gargantuan to Minuscule: The Morrison Menagerie, Part II". Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 162–242. ISBN 978-0-253-34870-8.
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