Chirostenotes

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Chirostenotes
Temporal range:
Ma
Skeletal diagram showing known elements
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: Caenagnathidae
Genus: Chirostenotes
Gilmore, 1924
Type species
Chirostenotes pergracilis
Gilmore, 1924
Synonyms
  • Macrophalangia canadensis Sternberg, 1932
  • Caenagnathus sternbergi? Cracraft, 1971

Chirostenotes (

oviraptorosaurian dinosaur from the late Cretaceous (about 76.5 million years ago) of Alberta, Canada. The type species is Chirostenotes pergracilis.[1]

History of discovery

Holotype hands

Chirostenotes has a confusing history of discovery and naming. The first fossils of Chirostenotes, a pair of hands, were in 1914 found by

dromaeosaurid.[2]

Chirostenotes was but the first name assigned. Feet were then found, specimen CMN 8538, and in 1932

ornithomimid. In 1936, its lower jaws, specimen CMN 8776, were found by Raymond Sternberg near Steveville and in 1940 he gave them the name Caenagnathus collinsi. The generic name means 'recent jaw' from Greek kainos, "new", and gnathos, "jaw"; the specific name honours William Henry Collins. The toothless jaws were first thought to be those of a bird.[4]

Slowly the precise relationship between the finds became clear. In 1960

Edwin Colbert and Dale Russell suggested that Chirostenotes and Macrophalangia were one and the same animal.[6] In 1976 Halszka Osmólska described Caenagnathus as an oviraptorosaurian.[7] In 1981 the announcement of Elmisaurus
, an Asian form of which both hand and feet had been preserved, showed the soundness of Colbert and Russell's conjecture.

Pelvic elements of assigned specimen TMP 1979.020.0001

In 1988, a specimen from storage since 1923 was discovered and studied by Philip J. Currie and Dale Russell. This fossil helped link the other discoveries into a single dinosaur. Since the first name applied to any of these remains was Chirostenotes, this were the only name that was recognized as valid.[8]

Currie and Russell also addressed the complicating issue of a possible second form being present in the material. In 1933

Leptorhynchos in 2013.[12]

Several larger skeletons from the early

In 2007 a

cladistic study by Philip Senter cast doubt on the idea that all of the large Dinosaur Park Formation fossils belonged to the same creature. Coding the original hand and jaw specimens separately showed that while the Caenagnathus holotype remained in the more basal position in the Caenagnathidae commonly assigned to it, the Chirostenotes pergracilis holotype was placed as an advanced oviraptorosaurian and an oviraptorid.[15] Subsequent studies found that the Caenagnathus jaws did in fact group together with other traditional caenagnathids, but not necessarily Chirostenotes.[14] New specimens described by Funston et al. (2015) and Funston & Currie (2020) indicated that Chirostenotes is a distinct form from Caenagnathus.[16][17]

Description

Life restoration

Chirostenotes was characterized by long arms ending in slender relatively straight claws, and long powerful legs with slender toes. In 2016 Paul estimated its length at 2.5 metres (8.2 ft) and its weight at 100 kg (220 lbs).[18]

Classification

The cladogram below follows an analysis by Funston & Currie in 2016, which found Elmisaurus within Caenagnathidae.[19]

Caenagnathidae

Microvenator celer

unnamed

Gigantoraptor erlianensis

unnamed

Hagryphus giganteus

Epichirostenotes curriei

Anzu wyliei

Caenagnathus collinsi

Elmisaurinae

Caenagnathasia martinsoni

Chirostenotes pergracilis

Citipes elegans

Apatoraptor pennatus

Elmisaurus rarus

Paleobiology

Mandible of Caenagnathus (left) compared to that of Chirostenotes (right)

Chirostenotes was probably an

Caenagnathus collinsi.[20]

In 2005 Phil Senter and J. Michael Parrish published a study on the hand function of Chirostenotes and found that its elongated second finger with its unusually straight claw may have been an adaptation to crevice probing. They suggested that Chirostenotes may have fed on soft-bodied prey that could be impaled by the second claw, such as grubs, as well as unarmored amphibians, reptiles, and mammals.[21] However, if Chirostenotes possessed the large primary feathers on its second finger that have been found in other oviraptorosaurs such as Caudipteryx, it would not have been able to engage in such behavior.[22]

Paleopathology

In 2001,

theropod dinosaurs and the implications for their behavior. They found that only one of the 17 Chirostenotes foot bones checked for stress fractures actually had them.[23]

See also

References

  1. ^ a b Gilmore, C.W. (1924). "A new coelurid dinosaur from the Belly River Cretaceous of Alberta". Canada Department of Mines Geological Survey Bulletin (Geological Series). 38 (43): 1–12.
  2. .
  3. ^ Sternberg, C.M. (1932). "Two new theropod dinosaurs from the Belly River Formation of Alberta". Canadian Field-Naturalist. 46 (5): 99–105.
  4. ^ Sternberg, R.M. (1940). "A toothless bird from the Cretaceous of Alberta". Journal of Paleontology. 14 (1): 81–85.
  5. ^ Wetmore, A. 1960. A classification for the birds of the world. Smithsonian Miscellaneous Collections 139 (11): 1–37
  6. ^ E.H. Colbert and D.A. Russell, 1969, "The small Cretaceous dinosaur Dromaeosaurus", Amer. Mus. Novit., No. 2380, pp. 1-49
  7. S2CID 4180155
    .
  8. .
  9. ^ Parks, W.A. (1933). "New species of dinosaurs and turtles from the Upper Cretaceous formations of Alberta". University of Toronto Studies, Geological Series. 34: 1–33.
  10. .
  11. .
  12. .
  13. ^ Robert M. Sullivan, Steven E. Jasinski and Mark P.A. Van Tomme (2011). "A new caenagnathid Ojoraptorsaurus boerei, n. gen., n. sp. (Dinosauria, Oviraptorosauria), from the Upper Ojo Alamo Formation (Naashoibito Member), San Juan Basin, New Mexico" (PDF). Fossil Record 3. New Mexico Museum of Natural History and Science Bulletin. 53: 418–428.
  14. ^
    PMID 24647078
    .
  15. .
  16. .
  17. .
  18. ^ Paul, Gregory S. (2016). The Princeton Field Guide to Dinosaurs 2nd Edition. New Jersey: Princeton University Press. p. 176.
  19. S2CID 131090028
    .
  20. .
  21. ^ Senter, P.; Parrish, J.M. (2005). "Functional analysis of the hands of the theropod dinosaur Chirostenotes pergracilis: evidence for an unusual paleoecological role". PaleoBios. 25: 9–19.
  22. ^ Naish, D. (2007). Feathers and Filaments of Dinosaurs, Part II Archived 2010-06-13 at the Wayback Machine Tetrapod Zoology, April 23, 2011.
  23. ^ 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.