Ostrich

Struthio is a genus of birds in the order Struthioniformes, whose members are the ostriches. It is part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There are two living species of ostrich, the common ostrich and the Somali ostrich.[2] They are large flightless birds of Africa who lay the largest eggs of any living land animal. With the ability to run at 70 km/h (43.5 mph), they are the fastest birds on land. It is farmed worldwide, particularly for its feathers as they are used as decoration and feather dusters. Its skin is also used for leather products.

Ostrich
Temporal range: Miocene-Holocene, 23–0 Ma
Struthio camelus australis in the West Coast National Park
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Struthioniformes
Family: Struthionidae
Genus: Struthio
Linnaeus, 1758[1]
Type species
Struthio camelus
Linnaeus, 1758
Species
Synonyms
  • Struthiolithus Brandt, 1873
  • Megaloscelornis Lydekker, 1879
  • Autruchon Temminick, 1840 fide Gray, 1841 (nomen nudum)

History of habitat

The genus Struthio was first described by Carl Linnaeus in 1758. The genus was used by Linnaeus and other early taxonomists to include the emu, rhea and cassowary, until they each were placed in their own genera.[1] The Somali ostrich (Struthio molybdophanes) has recently become recognized as a separate species by most authorities, while others are still reviewing the evidence.[3][4]

Evolution
Struthio camelus egg - MHNT
Size comparison (chicken egg, US dollar bill)

The earliest fossils of ostrich-like birds are Paleocene taxa from Europe.[5] Palaeotis and Remiornis from the Middle Eocene and unspecified ratite remains are known from the Eocene and Oligocene of Europe and Africa. These may have been early relatives of the ostriches, but their status is questionable, and they may in fact represent multiple lineages of flightless paleognaths.[5][6]

The earliest fossils from this genus are from the early Miocene (20–25 mya), and are from Africa, so it is proposed that they originated there. Then by the middle to late Miocene (5–13 mya) they had spread to Eurasia.[7] By about 12 mya they had evolved into the larger size of which we are familiar. By this time they had spread to Mongolia and later southern Africa.[8] While the relationship of the African fossil species is comparatively straightforward, many Asian species of ostrich have been described from fragmentary remains, and their interrelationships and how they relate to the African ostriches are confusing. In China, ostriches are known to have become extinct only around or even after the end of the last ice age; images of ostriches have been found there on prehistoric pottery and petroglyphs.[9][10][11]

Struthio ostriches once co-existed with another lineage of flightless didactyl birds, the eogruids. Though Olson 1985 classified these birds as stem-ostriches, they are otherwise universally considered to be related to cranes, any similarities being the result of convergent evolution. Competition from ostriches has been suggested to have caused the extinction of the eogruids,[12][13] though this has never been tested and both groups do co-exist in some sites.[14]

Distribution and habitat
A male Somali ostrich in a Kenyan savanna, showing its blueish neck
Ostrich with eggs

Today ostriches are only found natively in the wild in Africa, where they occur in a range of open arid and semi-arid habitats such as savannas and the Sahel, both north and south of the equatorial forest zone.[15] The Somali ostrich occurs in the Horn of Africa, having evolved isolated from the common ostrich by the geographic barrier of the East African Rift. In some areas, the common ostrich's Masai subspecies occurs alongside the Somali ostrich, but they are kept from interbreeding by behavioral and ecological differences.[16] The Arabian ostriches in Asia Minor and Arabia were hunted to extinction by the middle of the 20th century, and in Israel attempts to introduce North African ostriches to fill their ecological role have failed.[17] Escaped common ostriches in Australia have established feral populations.[18][19][20]

Species

There are nine known species in this genus, of which seven are extinct. In 2008, S. linxiaensis was transferred to the genus Orientornis.[21] Three additional species, S. pannonicus, S. dmanisensis and S. transcaucasicus, were transferred to the genus Pachystruthio in 2019.[22] Several additional fossil forms are ichnotaxa (that is, classified according to the organism's trace fossils such as footprints rather than its body) and their association with those described from distinctive bones is contentious and in need of revision pending more good material.[23]

The species are:

  • Prehistoric
    • †Struthio coppensi (Early Miocene of Elizabethfeld, Namibia)
    • †Struthio orlovi (Late Miocene of Moldavia)
    • †Struthio karingarabensis (Late Miocene – Early Pliocene of SW and CE Africa) – oospecies(?)
    • †Struthio kakesiensis (Early Pliocene of Laetoli, Tanzania) – oospecies
    • †Struthio wimani (Early Pliocene of China and Mongolia)
    • †Struthio daberasensis (Early – Middle Pliocene of Namibia) – oospecies
    • †Struthio brachydactylus (Pliocene of Ukraine)
    • †Struthio chersonensis (Pliocene of SE Europe to WC Asia) – oospecies
  • Late Pleistocene - Holocene
    • †Struthio oldawayi (Late Pleistocene of Tanzania) – probably subspecies of S. camelus[24]
    • †Struthio asiaticus, Asian ostrich (Early Pliocene – Early Holocene of Central Asia to China? and Morocco)
    • †Struthio anderssoni, East Asian ostrich (Late Pleistocene of China to Mongolia)[10][25] - oospecies(?)
    • Struthio camelus, Common ostrich
    • Struthio molybdophanes, Somali ostrich

Footnotes
  1. Gray, G.R. (1855)
  2. "Seagull Publishers:: K-8 segment | Books | Practice manuals". Retrieved 2020-11-11.
  3. Gil, F. & Donsker D. (2012)
  4. Birdlife International (2012)
  5. Buffetaut, E.; Angst, D. (2014). "Stratigraphic distribution of large flightless birds in the Palaeogene of Europe and its palaeobiological and palaeogeographical implications". Earth-Science Reviews. 138: 394–408. doi:10.1016/j.earscirev.2014.07.001.
  6. Agnolin et al, Unexpected diversity of ratites (Aves, Palaeognathae) in the early Cenozoic of South America: palaeobiogeographical implications. Alcheringa An Australasian Journal of Palaeontology · July 2016 DOI: 10.1080/03115518.2016.1184898
  7. Hou, L. et al. (2005)
  8. Davies, S.J.J.F. (2003)
  9. Doar, B.G. (2007) "Genitalia, Totems and Painted Pottery: New Ceramic Discoveries in Gansu and Surrounding Areas". China Heritage Quarterly
  10. Janz, Lisa; et al. (2009). "Dating North Asian surface assemblages with ostrich eggshell: Implications for palaeoecology and extirpation". Journal of Archaeological Science. 36 (9): 1982–1989. doi:10.1016/j.jas.2009.05.012.
  11. Andersson, J. G. (1923). "Essays on the cenozoic of northern China". Memoirs of the Geological Survey of China (Peking), Series A. 3: 1–152 (53–77).
  12. Kurochkin, E.N. (1976). "A survey of the Paleogene birds of Asia". Smithsonian Contributions to Paleobiology. 27: 75–86.
  13. Kurochkin, E.N. (1981). "New representatives and evolution of two archaic gruiform families in Eurasia". Transactions of the Soviet-Mongolian Paleontological Expedition. 15: 59–85.
  14. Zelenkov, Nikita; Boev, Zlatozar; Lazaridis, Georgios (2015). "A large ergilornithine (Aves, Gruiformes) from the Late Miocene of the Balkan Peninsula". Paläontologische Zeitschrift. 90: 145–151. doi:10.1007/s12542-015-0279-z.
  15. Donegan, Keenan (2002). "Struthio camelus". Animal Diversity Web. University of Michigan Museum of Zoology.
  16. Freitag, Stephanie & Robinson, Terence J. (1993). "Phylogeographic patterns in mitochondrial DNA of the Ostrich (Struthio camelus)" (PDF). The Auk. 110 (3): 614–622. doi:10.2307/4088425. JSTOR 4088425.
  17. Rinat, Zafrir (25 December 2007). "The Bitter Fate of Ostriches in the Wild". Haaretz. Tel Aviv. Retrieved 10 January 2017.
  18. Ostriches in Australia – and near my home. trevorsbirding.com (13 September 2007)
  19. "The outback ostriches — Australia's loneliest birds". www.abc.net.au. 2018-09-01. Retrieved 2021-02-10.
  20. "Common Ostrich (Struthio camelus)". iNaturalist Australia. Retrieved 2021-02-10.
  21. Wang, S. (2008). "Rediscussion in the taxonomic assignment of "Struthio linxiaensis Hou, et al., 2005". Acta Paleotologica Sinica. 47: 362–368.
  22. Zelenkov, N. V.; Lavrov, A. V.; Startsev, D. B.; Vislobokova, I. A.; Lopatin, A. V. (2019). "A giant early Pleistocene bird from eastern Europe: unexpected component of terrestrial faunas at the time of early Homo arrival". Journal of Vertebrate Paleontology: e1605521. doi:10.1080/02724634.2019.1605521.
  23. Bibi, Faysal; Shabel, Alan B.; Kraatz, Brian P.; Stidham, Thomas A. (2006). "New Fossil Ratite (Aves: Palaeognathae) Eggshell Discoveries from the Late Miocene Baynunah Foramation of the United Arab Emirates, Arabian Peninsula" (PDF). Palaeontologia Electronica. 9 (1): 2A. ISSN 1094-8074.
  24. https://olduvai-paleo.org/specimen/ovpp-struthio-8/
  25. J. G. Andersson, Essays on the cenozoic of northern China. Memoirs of the Geological Survey of China (Peking), Series A, No. 3 (1923), pp. 1–152, especially pp. 53–77: "On the occurrence of fossil remains of Struthionidae in China."; and J. G. Andersson, Research into the prehistory of the Chinese. Bulletin of the Museum of Far Eastern Antiquities 15 (1943), 1–300, plus 200 plates.

References
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