Megalochelys

Megalochelys ("great turtle") is an extinct genus of tortoises that lived from the Miocene to Pleistocene. They are noted for their giant size, which is among the largest of any known testudine, with a maximum carapace length over 2 m (6.5 ft) in M. atlas. During the dry glacial periods it ranged from western India and Pakistan (possibly even as far west as southern and eastern Europe) to as far east as Sulawesi and Timor in Indonesia, though the island specimens likely represent distinct species.[4]

Megalochelys
Temporal range:
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[1][2]
Synonyms
  • Colossochelys Falconer & Cautley, 1844[1][3]

Description

One species of Megalochelys, M. atlas, is the largest known tortoise, with a shell length of 2 m (6.6 ft) and even 2.7 m (8.9 ft), and an approximate total height of 1.8 m (5.9 ft).[5] 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.[6] However, weights based on volumetric displacement of the skeleton,[7] or inferences based on two-dimensional skeletal drawings,[8] indicate that M. atlas was probably closer to 1,000 to 2,000 kg (2,200 to 4,400 lb) in mass. M. atlas is thus the largest known tortoise. The only larger turtles were the marine Archelon and Protostega from the Cretaceous Period, and the aquatic, freshwater Stupendemys of the South American Late Miocene. A similarly gigantic tortoise, Titanochelon, is known from the Miocene to Pleistocene of Europe, which had shell lengths of up to 2 m (6.6 ft).

Like the modern Galápagos tortoise, M. atlas' weight was supported by four elephantine feet. Like other tortoises, it is thought to have been herbivorous.

Taxonomy
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.[1]

  • Megalochelys atlas Falconer and Cautley, 1844[1][3] Late Miocene to Early Pleistocene, India (Sivalik Hills), Myanmar, ?Thailand
  • Megalochelys cautleyi Lydekker, 1889[1][9] Late Pliocene to Early Pleistocene, India (Sivalik Hills) probable nomen dubium.[1]
  • Megalochelys margae[1] Early Pleistocene, Sulawesi, Indonesia. Size estimation between 1,4-1,9 m long.[1]
  • Megalochelys sondaari Karl and Staesche, 2007 [1] Early Pleistocene (until 1.7 ma) Luzon, Philippines
  • Megalochelys sp. Middle-Late Pleistocene (about 0.8-0.12 Mya) Timor, Indonesia[4]
  • Megalochelys sp. Early Pleistocene (until 1.2 Mya) Java, Indonesia[4]
  • Megalochelys sp. Early Pleistocene (1.4-1.3 Mya[10]) Flores, Indonesia[4]

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).[11]

Extinction

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.[1]

See also
  • 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
  1. 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.
  2. Falconer, H. and Cautley, P.T. 1837. On additional fossil species of the order Quadrumana from the Siwalik Hills. Journal of the Asiatic Society of Bengal 6:354–360.
  3. Falconer, H. and 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. Proceedings of the Zoological Society of London 1844(12):54–84.
  4. Rhodin, Anders; Pritchard, Peter; van Dijk, Peter Paul; Saumure, Raymond; Buhlmann, Kurt; Iverson, John; Mittermeier, Russell, eds. (2015-04-16). 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.
  5. Hirayama R, Sonoda T, Takai M, Htike T, Maung Thein ZM, Takahashi A. 2015. Megalochelys: gigantic tortoise from the Neogene of Myanmar. PeerJ PrePrints 3:e961v1 https://doi.org/10.7287/peerj.preprints.961v1
  6. Orenstein, R. 2001. Survivors in Armor: Turtles, Tortoises, and Terrapins. Key Porter Books Ltd.
  7. Brown, B. 1931. The Largest Known Land Tortoise. Nat. Hist. Vol. 31:184–187.
  8. Gregory S. Paul; Guy D. Leahy (1994). "Terramegathermy in the time of the titans: Restoring the metabolics of colossal dinosaurs" (PDF). The Paleontological Society Special Publications. 7: Dino Fest: 177–198. doi:10.1017/S2475262200009515. Archived from the original (PDF) on 20 September 2022.
  9. 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.
  10. 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.
  11. Vlachos, Evangelos; Rabi, Márton (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. PMID 34706483. S2CID 90619565.
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