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Megalochelys

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Megalochelys
Temporal range: Late Miocene?Middle Pleistocene
M. atlas skeleton at the American Museum of Natural History
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Testudines
Suborder: Cryptodira
Superfamily: Testudinoidea
Family: Testudinidae
Genus: † Megalochelys
Falconer & Cautley , 1837
Type species
Megalochelys atlas
(Falconer and Cautley, 1844)
Species

See text

Synonyms
  • Colossochelys Falconer & Cautley, 1844

Megalochelys ("great turtle") is an extinct genus of tortoises that lived from the Miocene to Pleistocene . They are noted for their giant size, the largest known for any tortoise, with a maximum carapace length of over 2 m (6.5 ft) in M. atlas . The genus ranged from western India and Pakistan to as far east as Sulawesi and Timor in Indonesia , though the island specimens likely represent distinct species. [1]

Description [ edit ]

One species of Megalochelys, M. atlas , is the largest known tortoise , with shells of 2 m (6 ft 7 in) in length having been reported. [2] Popular weight estimates for this taxon have varied greatly with the highest estimates reaching up to 4,000 kg (8,800 lb) in some instances. [3] However, weights based on volumetric displacement of the skeleton suggest a mass of around 1,000 kg (2,200 lb). [4] M. atlas is thus the largest known tortoise. [2] Some island species were considerably smaller, with the Philippine species Megalochelys sondaari only having a carapace length of 70?90 cm (2 ft 4 in ? 2 ft 11 in). [1] The shell of Megalochelys is prominently domed and is proportionally wide, with large openings for the limbs. [2] The shell of Megalochelys is relatively thin despite its size, [5] though the epiplastron (the frontmost-portion of the lower carapace) was forked and very thick, [6] Such forked epiplastra are found in some living tortoises, where they are used for combat and shoving contests between males. [2] The skull of Megalochelys could grow over 30 cm (0.98 ft) in length, and had a deep nasal region and a deep and rather short snout, similar to living Aldabra giant tortoises . [2]

Taxonomy [ edit ]

The genus Megalochelys was first named in 1837 Hugh Falconer and Proby Cautley based on remains found in the Sivalik Hills of northern India with species Megalochelys sivalensis. [7] However, later in 1844, Falconer and Cautley decided to rename the species Colossochelys atlas [5] as they considered the original name "not to convey a sufficiently expressive idea of the size". [6] During the late 19th century and much of the 20th century, Megalochelys / Colossochelys was considered synonymous with Testudo , [8] and later Geochelone . [9] [10] Today, Colossochelys is regarded as a junior synonym of Megalochelys . The original species name M. sivalensis is regarded as a nomen nudum due to lacking a proper description (though the genus name is valid due to differing ICZN standards on the naming of genera and species) making M. atlas , which was accompanied by a proper description, the valid name for this species, [11] though some authors have argued for the validity of Megalochelys sivalensis. [12]

M. margae fossilized humerus bone from Saribatue, Wallanae river, South Sulawesi

Megalochelys is the original and valid name for what has been called Colossochelys . It contains three named species with several unnamed taxa. [11]

  • Megalochelys atlas Falconer and Cautley, 1844 [11] Late Miocene to Early Pleistocene, India ( Sivalik Hills ), Myanmar, ?Thailand
  • Megalochelys cautleyi Lydekker , 1889 [11] [13] Late Pliocene to Early Pleistocene, India (Sivalik Hills) probable nomen dubium . [11]
  • Megalochelys margae [11] Early Pleistocene, Sulawesi , Indonesia. Size estimation between 1.4-1.9 m long. [11]
  • Megalochelys sondaari Karl and Staesche, 2007 [11] Early Pleistocene (until 1.7 ma) Luzon , Philippines
  • Megalochelys sp. Middle-Late Pleistocene (about 0.8-0.12 Mya) Timor , Indonesia [1]
  • Megalochelys sp. Early Pleistocene (until 1.2 Mya) Java , Indonesia [1]
  • Megalochelys sp. Early Pleistocene (1.4-1.3 Mya [14] ) Flores , Indonesia [1]

Cladistic analysis has suggested that Megalochelys' closest living relative is Centrochelys (the African spurred tortoise ), with both also being closely related to Geochelone ( the star tortoises). [15]

Extinction [ edit ]

The genus is suspected to have gone extinct due to the arrival of Homo erectus , due to staggered extinctions on islands coinciding with the arrival of H. erectus in these regions, as well as evidence of exploitation by H. erectus . The genus was largely extinct by the end of the Early Pleistocene , but persisted on Timor into the Middle Pleistocene . [11]

See also [ edit ]

  • Titanochelon a similarly giant tortoise known from the Miocene-Early Pleistocene of Europe
  • Archelon : A Late Cretaceous marine turtle and the largest turtle yet discovered.
  • Stupendemys : the largest freshwater turtle to have ever lived, comparable in size to Megalochelys atlas

References [ edit ]

  1. ^ a b c d e Rhodin, Anders; Pritchard, Peter; van Dijk, Peter Paul; Saumure, Raymond; Buhlmann, Kurt; Iverson, John; Mittermeier, Russell, eds. (2015-04-16). "Turtles and Tortoises of the World During the Rise and Global Spread of Humanity: First Checklist and Review of Extinct Pleistocene and Holocene Chelonians". Conservation Biology of Freshwater Turtles and Tortoises . Chelonian Research Monographs. Vol. 5 (First ed.). Chelonian Research Foundation. doi : 10.3854/crm.5.000e.fossil.checklist.v1.2015 . ISBN   978-0-9653540-9-7 .
  2. ^ a b c d e Naish, Darren (2024-01-31). "Megalochelys, Truly a Giant Tortoise" . Tetrapod Zoology . Retrieved 2024-05-30 .
  3. ^ Orenstein, R. 2001. Survivors in Armor: Turtles, Tortoises, and Terrapins. Key Porter Books Ltd.
  4. ^ Brown, B. 1931. The Largest Known Land Tortoise. Nat. Hist. Vol. 31:184?187.
  5. ^ a b Falconer, H., Cautley, P.T. 1844. Communication on the Colossochelys atlas, A Fossil Tortoise of Enormous Size from the Tertiary Strata of the Siwalk Hills in the North of India. Proc. Zool. Soc. Lond. 12:54?84.
  6. ^ a b Murchison, C.D. 1868. Palaeontological Memoirs and Notes of the late Hugh Falconer: With a Biographical Sketch of the Author Compiled and Edited by Charles Murchison. Rob. Hardwicke, 1868.
  7. ^ Falconer, H., Cautley, P.T. 1837. On Additional Fossil Species of the Order Quadrumana from the Siwalik Hills. J. Asiatic Soc. Bengal. Vol. 6:354?360.
  8. ^ Lydekker, R. 1889. Catalogue of the Fossil Reptilia and Amphibia in the British Museum. Part III. Chelonia. London: Brit. Mus. Nat. Hist. 3:74
  9. ^ Hooijer, D.A. 1971. A Giant Land Tortoise, Geochelone atlas (Falconer and Cautley), from the Pleistocene of Timor. Proc. Koninklijke Nederlandsche Akademie van Wetenschappen, Ser. B. Phys. Sci. 74(5):504?525.
  10. ^ Auffenberg, W. 1974. Checklist of Fossil Land Tortoises (Testudinidae). Bull. FL. State Mus. Biol. Sci. 18:121?251.
  11. ^ a b c d e f g h i Rhodin, A.G.J.; Thomson, S.; Georgalis, G.; Karl, H.-V.; Danilov, I.G.; Takahashi, A.; de la Fuente, M.S.; Bourque, J.R.; Delfino M.; Bour, R.; Iverson, J.B.; Shaffer, H.B.; van Dijk, P.P.; et al. (Turtle Extinctions Working Group) (2015). "Turtles and tortoises of the world during the rise and global spread of humanity: first checklist and review of extinct Pleistocene and Holocene chelonians" . Chelonian Research Monographs . 5 (8): 000e.1?66. doi : 10.3854/crm.5.000e.fossil.checklist.v1.2015 . hdl : 11336/62240 .
  12. ^ Vlachos, Evangelos (2019-08-30). "On the nomenclature of the largest tortoise that ever lived: Megalochelys sivalensis Falconer & Cautley, 1837 vs. Colossochelys atlas Falconer & Cautley, 1844 (Reptilia, Testudinidae)" . The Bulletin of Zoological Nomenclature . 76 (1): 162. doi : 10.21805/bzn.v76.a050 . ISSN   0007-5167 .
  13. ^ Lydekker, R. 1889. Catalogue of the Fossil Reptilia and Amphibia in the British Museum. Part III. Chelonia. London: British Museum of Natural History, 239 pp.
  14. ^ van den Bergh, Gerrit D.; Alloway, Brent V.; Storey, Michael; Setiawan, Ruly; Yurnaldi, Dida; Kurniawan, Iwan; Moore, Mark W.; Jatmiko; Brumm, Adam; Flude, Stephanie; Sutikna, Thomas; Setiyabudi, Erick; Prasetyo, Unggul W.; Puspaningrum, Mika R.; Yoga, Ifan (October 2022). "An integrative geochronological framework for the Pleistocene So'a basin (Flores, Indonesia), and its implications for faunal turnover and hominin arrival" . Quaternary Science Reviews . 294 : 107721. Bibcode : 2022QSRv..29407721V . doi : 10.1016/j.quascirev.2022.107721 . hdl : 10072/418777 . S2CID   252290750 .
  15. ^ Vlachos, Evangelos; Rabi, Marton (December 2018). "Total evidence analysis and body size evolution of extant and extinct tortoises (Testudines: Cryptodira: Pan-Testudinidae)" . Cladistics . 34 (6): 652?683. doi : 10.1111/cla.12227 . hdl : 11336/98248 . PMID   34706483 . S2CID   90619565 .

External links [ edit ]

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