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Mononykus Temporal range: Late Cretaceous, ~70 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Reconstructed skeleton at the American Museum of Natural History
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Family:	†Alvarezsauridae
Subfamily:	†Parvicursorinae
Tribe:	†Mononykini
Genus:	†Mononykus Perle et al., 1993
Type species
†Mononykus olecranus Perle et al., 1993
Synonyms
Mononychus olecranus Perle et al., 1993 (preoccupied generic name)

Mononykus (/məˈnɒnɪkəs/ mə-NON-ik-əs, sometimes /ˌmɒnoʊˈnaɪkəs/ MON-oh-NY-kəs; meaning "one claw") is a genus of alvarezsaurid dinosaur that lived during the Late Cretaceous in what is now Asia on the Nemegt Formation, about 70 million years ago.

Mononykus was a very small theropod, estimated around 1 to 1.2 metres (3.3 to 3.9 ft) in length with a weight of 3.5 kilograms (7.7 lb). As in Shuvuuia, Mononykus likely developed a shaggy feathering. It was lightly built with long, thin legs and highly reduced and specialized forelimbs that were likely used for foraging termite mounds or other insect colonies.

History of discovery

Mononykus is represented by a single holotype specimen, catalog number MPC-D 107/6 (formerly IGM 107/6). It was collected in 1987 from the Bügiin Tsav locality of the Nemegt Formation, Gobi Desert. This specimen consists of a partial skeleton lacking a tail, and only small fragments of skull bones, including a complete braincase. Mononykus was originally named Mononychus in 1993, but later that year, it was renamed because the original name had already been used for a beetle named by Johann Schueppel, a German entomologist. Several other specimens were later misclassified as Mononykus, including specimens with partial tails (initially misinterpreted as being very short, though later specimens showed they were long and thin) and complete skulls showing a distinct, mostly toothless form. However, these specimens have since been reclassified in the new genus Shuvuuia. Because of this, many reconstructions of Mononykus in art and mounted skeletons in museums are in fact based mainly on Shuvuuia.

While Mononykus was formally described in the 1990s, it was reported that a specimen possibly belonging to this genus had already been unearthed by the Andrews expedition decades before. The specimen had been in the American Museum of Natural History collection, labeled simply as "bird-like dinosaur". However, given the reassignment of the other specimens to related genera, and the difference in age (the AMNH specimen is from the older Djadochta Formation), it is unlikely to be Mononykus.

In 2019, Sungjin Lee and colleagues referred a new specimen from the Nemegt Formation, MPC-D 100/206. This specimen consists of seven caudal vertebrae with a partial left hindlimb, and was discovered on a low slope of the Altan Uul III locality in 2008 by an international team of the Korea-Mongolia International Dinosaur Expedition (KID). The team also found a small assemblage of theropod fossils comprising specimens from other taxa such as Gobiraptor and Nemegtonykus.

Description

Mononykus was a small dinosaur around 1 to 1.2 metres (3.3 to 3.9 ft) long and weighing 3.5 kilograms (7.7 lb). Other characteristics include fused wrist bones similar to those of birds, and a keeled breastbone. It differed from close relatives Shuvuuia and Parvicursor in several details of its skeleton, including a pubic bone that is triangular in cross section, and different proportions in the toe bones. Mononykus likely had a covering of feathers, as in the fossils of its relative Shuvuuia feather traces were discovered, proving that Alvarezsauridae were among the theropod lineages with feathery or downy integument. The inner ear structures of Mononykus and its relatives closely resembles those of Barn Owls. For this reason it is possible Mononykus also had a facial disc of specialized feathers, similar to extant owls, that served to catch sound and direct it to the ears.

Paleobiology

Mononykus was a member of the family Alvarezsauridae and, like its relatives, had very strange, stubby forearms with one large, approximately 7.5-centimetre (3.0 in) long claw (hence its name). The other two claws had disappeared (however, a close relative of Mononykus, Shuvuuia, had two vestigial claws, alongside one large claw). The purpose of these highly specialized arms is still a mystery, but some scientists have suggested they were used to break open termite mounds (like modern anteaters), and therefore it is possible that they fed primarily on insects.

In a 2001 study conducted by Bruce Rothschild and other paleontologists, 15 foot bones referred to Mononykus were examined for signs of stress fracture, but none were found.

References

1. Perle, A.; Norell, M. A.; Chiappe, L. M.; Clark, J. M. (1993). "Flightless bird from the Cretaceous of Mongolia". Nature. 362: 623−626. Bibcode:1993Natur.362..623A. doi:10.1038/362623a0.
2. Perle, A.; Chiappe, L. M.; Rinchen, B.; Clark, J. M.; Norell, M. A. (1994). "Skeletal morphology of Mononykus olecranus (Theropoda, Avialae) from the late Cretaceous of Mongolia". American Museum Novitates (3105): 1−29. hdl:2246/4936.
3. Perle, A.; Norell, M. A.; Chiappe, L. M.; Clark, J. M. (1993). "Correction: Flightless bird from the Cretaceous of Mongolia". Nature. 363 (188). doi:10.1038/363188a0.
4. Suzuki, S., Chiappe, L. M., Dyke, G.J., Watabe, M., Barsbold, R., and Tsogtbaatar, K. (2002). "A new specimen of Shuvuuia deserti Chiappe et al., 1998 from the Mongolian Late Cretaceous with a discussion of the relationships of alvarezsaurids to other theropod dinosaurs." Contributions in Science, 494: 1–18.
5. Chiappe, L. M., Norell, M. and Clark (1998). "The skull of a relative of the stem-group bird Mononykus." Nature, 392: 275–278.
6. Dinosaurs of the Gobi. Mongolia: BBC Horizon. 1993.
7. Mortimer, M. (2004), "Ornithomimosauria" Archived 2013-09-29 at the Wayback Machine, The Theropod Database, accessed June 30, 2009.
8. Lee, S.; Park, J.-Y.; Lee, Y.-N.; Kim, S.-H.; Lü, J.; Barsbold, R.; Tsogtbaatar, K. (2019). "A new alvarezsaurid dinosaur from the Nemegt Formation of Mongolia". Scientific Reports. 9 (1): 15493. Bibcode:2019NatSR...915493L. doi:10.1038/s41598-019-52021-y. PMC 6820876. PMID 31664171.
9. Choiniere, J. N.; Xu, X.; Clark, J. M.; Forster, C. A.; Guo, Y.; Han, F. (2010). "A basal alvarezsauroid theropod from the Early Late Jurassic of Xinjiang, China". Science. 327 (5965): 571–574. doi:10.1126/science.1182143. PMID 20110503. Supporting Online Material
10. Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs (2nd ed.). Princeton, New Jersey: Princeton University Press. p. 137. ISBN 9780691167664.
11. Schweitzer, M. H., J. A. Watt, R. Avci, L. Knapp, L. Chiappe, M. Norell & M. Marshall. (1999). "Beta-keratin specific immunological reactivity in feather-like structures of the Cretaceous alvarezsaurid, Shuvuuia deserti." Journal of Experimental Zoology, 285: 146–157.
12. ^ "'Prehistoric Planet,' a Stunning New Series, Depicts Dinosaurs Like Never Before | Audubon". www.audubon.org. May 23, 2022. Retrieved 2024-05-16.
13. Choiniere, Jonah N.; Neenan, James M.; Schmitz, Lars; Ford, David P.; Chapelle, Kimberley E. J.; Balanoff, Amy M.; Sipla, Justin S.; Georgi, Justin A.; Walsh, Stig A.; Norell, Mark A.; Xu, Xing; Clark, James M.; Benson, Roger B. J. (2021-05-07). "Evolution of vision and hearing modalities in theropod dinosaurs". Science. 372 (6542): 610–613. doi:10.1126/science.abe7941. ISSN 0036-8075.
14. Senter, P. (2005). "Function in the stunted forelimbs of Mononykus olecranus (Theropoda), a dinosaurian anteater". Paleobiology Vol. 31, No. 3 pp. 373–381.
15. 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.

External links

• In chinese but with pictures and taxon in english

v t e Maniraptora
Kingdom: Animalia Phylum: Chordata Clade: Dinosauria Clade: Theropoda Clade: Maniraptoriformes Avemetatarsalia see Avemetatarsalia Theropoda see Theropoda Maniraptora see below↓
Maniraptora Maniraptora †Elopteryx? †Fukuivenator? †Kakuru? †Migmanychion †Yaverlandia? †Alvarezsauroidea Achillesaurus Aorun? Bannykus Bonapartenykus Haplocheirus Patagonykus Shishugounykus Tugulusaurus? Xiyunykus Alvarezsauridae Achillesaurus? Alnashetri Alvarezsaurus Bonapartenykus? Bradycneme Heptasteornis Patagonykus? Parvicursorinae Dzharaonyx Jaculinykus Khulsanurus Kol? Nemegtonykus Ondogurvel Parvicursor Qiupanykus Trierarchuncus Ceratonykini Albinykus Ceratonykus Xixianykus Mononykini Albertonykus Linhenykus Mononykus Shuvuuia †Therizinosauria Eshanosaurus? Falcarius Fukuivenator? Jianchangosaurus Lingyuanosaurus Therizinosauroidea Alxasaurus Beipiaosaurus Enigmosaurus Martharaptor Suzhousaurus Therizinosauridae Erliansaurus Erlikosaurus Nanshiungosaurus Neimongosaurus Nothronychus Paralitherizinosaurus Segnosaurus Therizinosaurus Pennaraptora †Oviraptorosauria see Oviraptorosauria Paraves see below↓
Paraves Paraves †Palaeopteryx? †Pneumatoraptor †Rahonavis †Scansoriopterygidae? Ambopteryx Epidexipteryx Scansoriopteryx Yi †Anchiornithidae Anchiornis Aurornis Caihong Eosinopteryx Fujianvenator Liaoningvenator? Ostromia Pedopenna Serikornis Xiaotingia Yixianosaurus †Archaeopterygidae Alcmonavis? Archaeopteryx Wellnhoferia Anchiornithidae? †Dromaeosauridae see Dromaeosauridae †Troodontidae see Troodontidae Avialae †Alcmonavis †Balaur? †Cretaaviculus? †Fukuipteryx †Overoraptor †Rahonavis? †Yandangornis †Zhongornis †Anchiornithidae? †Archaeopterygidae? †Scansoriopterygidae? †Jeholornithiformes Dalianraptor? Jeholornis Jixiangornis? Kompsornis Neimengornis Pygostylia †"Proornis" †Omnivoropterygidae? Omnivoropteryx Sapeornis †Confuciusornithidae Changchengornis Confuciusornis Eoconfuciusornis Yangavis †Jinguofortisidae Chongmingia Cratonavis Jinguofortis Ornithothoraces †Enantiornithes see Enantiornithes Euornithes see below↓
Euornithes Euornithes †Archaeorhynchus †Bellulornis †Brevidentavis †Changmaornis †Changzuiornis †Chaoyangia †Dingavis †Eogranivora †Gargantuavis? †Hollanda †Horezmavis †Jianchangornis †Jiuquanornis †Juehuaornis †Kaririavis †Meemannavis †Platanavis †Vorona †Wyleyia? †Xinghaiornis †Yumenornis †Zhongjianornis †Schizoouridae Mengciusornis Schizooura †Patagopterygiformes Alamitornis Kuszholia? Patagopteryx †Ambiortiformes Ambiortus Apsaravis? Palintropus? †Hongshanornithidae Archaeornithura Hongshanornis Longicrusavis Parahongshanornis Tianyuornis †Songlingornithidae Hollanda? Piscivoravis? Songlingornis Yanornis? Yixianornis? †Yanornithidae Abitusavis Similiyanornis Yanornis †Gansuidae? Changzuiornis Gansus Hollanda? Iteravis Khinganornis Shuilingornis Ornithurae †Antarcticavis? †Apatornis †Cerebavis †Gallornis †Guildavis †Iaceornis †Kookne †Limenavis †Tingmiatornis †Ichthyornithes Ichthyornis Janavis †Hesperornithes Baptornis Brodavis Chupkaornis Enaliornis Judinornis Pasquiaornis Potamornis Hesperornithidae Asiahesperornis Canadaga Fumicollis Hesperornis Parahesperornis †Vegaviidae Australornis? Maaqwi? Neogaeornis? Polarornis Vegavis †Cimolopterygidae Ceramornis Cimolopteryx Lamarqueavis? Aves / Neornithes see below↓
Aves / Neornithes Palaeognathae see Palaeognathae Neognathae Neoaves Galloanserae Anserimorphae see Anserimorphae Pangalliformes see Pangalliformes Incertae sedis †Asteriornis †Perplexicervix †Qinornis? †Dromornithidae Barawertornis Dromornis Genyornis Ilbandornis †Gastornithiformes Brontornis? Gastornis Dromornithidae? †Pelagornithidae Aequornis Caspiodontornis Cyphornis Dasornis Gigantornis Laornis? Lutetodontopteris Macrodontopteryx Manu? Odontopteryx Odontoptila Osteodontornis Palaeochenoides Pelagornis Proceriavis? Protodontopteryx Protopelicanus? Pseudodontornis Tympanonesiotes
See also: Archaeornithes Carinatae Deinonychosauria Odontognathae Odontornithes Sauriurae Unenlagiidae Category

• Late Cretaceous dinosaurs of Asia
• Nemegt fauna
• Alvarezsaurs
• Fossil taxa described in 1993
• Taxa named by Altangerel Perle
• Taxa named by Luis M. Chiappe