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''Megalochelys'' ("great turtle") is an extinct genus of
cryptodira The Cryptodira ('' el, hidden neck'') are a suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira (side-necked turtles) in that they lower their necks and pull the heads straight back into th ...
n
tortoise Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like othe ...
s that lived from the
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent ...
to
Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed i ...
. 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 India, officially the Republic of India ( Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the ...
and
Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's fifth-most populous country, with a population of almost 243 million people, and has the world's second-la ...
(possibly even as far west as southern and eastern
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
) to as far east as
Sulawesi Sulawesi (), also known as Celebes (), is an island in Indonesia. One of the four Greater Sunda Islands, and the List of islands by area, world's eleventh-largest island, it is situated east of Borneo, west of the Maluku Islands, and south of ...
and
Timor Timor is an island at the southern end of Maritime Southeast Asia, in the north of the Timor Sea. The island is divided between the sovereign states of East Timor on the eastern part and Indonesia on the western part. The Indonesian part, al ...
in
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
, though the island specimens likely represent distinct species.


Description

One species of ''Megalochelys,'' ''M. atlas'', is the largest known
tortoise Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like othe ...
, with a shell length of and even , and an approximate total height of . Popular weight estimates for this taxon have varied greatly with the highest estimates reaching up to in some instances.Orenstein, R. 2001. Survivors in Armor: Turtles, Tortoises, and Terrapins. Key Porter Books Ltd. However, weights based on volumetric displacement of the skeleton,Brown, B. 1931. The Largest Known Land Tortoise. Nat. Hist. Vol. 31:184–187. or inferences based on two-dimensional skeletal drawings, indicate that ''M. atlas'' was probably closer to in mass. ''M. atlas'' is thus the largest known tortoise. The only larger turtles were the marine '' Archelon'' and '' Protostega'' from the
Cretaceous Period The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
, and the aquatic, freshwater '' Stupendemys'' of the
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...
n
Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million years ago) to 5.333 Ma. The ...
. A similarly gigantic tortoise, '' Titanochelon'', is known from the Miocene to Pleistocene of Europe, which had shell lengths of up to . Like the modern Galápagos tortoise, ''M. atlas weight was supported by four
elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae ...
ine feet. Like other tortoises, it is thought to have been herbivorous.


Taxonomy

''Megalochelys'' is the original and valid name for what has been called ''Colossochelys''. It contains three named species with several unnamed taxa. *''Megalochelys atlas'' Falconer and Cautley, 1844 Late Miocene to Early Pleistocene, India (
Sivalik Hills The Sivalik Hills, also known as the Shivalik Hills and Churia Hills, are a mountain range of the outer Himalayas that stretches over about from the Indus River eastwards close to the Brahmaputra River, spanning the northern parts of the Ind ...
), Myanmar, ?Thailand *''Megalochelys cautleyi'' Lydekker, 1889Lydekker, R. 1889. Catalogue of the Fossil Reptilia and Amphibia in the British Museum. Part III. Chelonia. London: British Museum of Natural History, 239 pp. Late Pliocene to Early Pleistocene, India (Sivalik Hills) probable ''
nomen dubium In binomial nomenclature, a ''nomen dubium'' ( Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a ...
.'' *''Megalochelys margae'' Early Pleistocene,
Sulawesi Sulawesi (), also known as Celebes (), is an island in Indonesia. One of the four Greater Sunda Islands, and the List of islands by area, world's eleventh-largest island, it is situated east of Borneo, west of the Maluku Islands, and south of ...
, Indonesia *''Megalochelys sondaari'' Karl and Staesche, 2007 Early Pleistocene (until 1.7 ma)
Luzon Luzon (; ) is the largest and most populous island in the Philippines. Located in the northern portion of the Philippines archipelago, it is the economic and political center of the nation, being home to the country's capital city, Manila, a ...
, Philippines *''Megalochelys'' sp. Middle-Late Pleistocene (about 0.8-0.12 Mya)
Timor Timor is an island at the southern end of Maritime Southeast Asia, in the north of the Timor Sea. The island is divided between the sovereign states of East Timor on the eastern part and Indonesia on the western part. The Indonesian part, al ...
, Indonesia *''Megalochelys'' sp. Early Pleistocene (until 1.2 Mya)
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...
, Indonesia *''Megalochelys'' sp. Early Pleistocene (until 0.9 Mya)
Flores Flores is one of the Lesser Sunda Islands, a group of islands in the eastern half of Indonesia. Including the Komodo Islands off its west coast (but excluding the Solor Archipelago to the east of Flores), the land area is 15,530.58 km2, and t ...
, Indonesia Cladistic analysis has suggested that ''Megalochelys'' closest living relative is '' Centrochelys'' (the African spurred tortoise), with both also being closely related to ''
Geochelone ''Geochelone'' is a genus of tortoises. ''Geochelone'' tortoises, which are also known as typical tortoises or terrestrial turtles, can be found in southern Asia. They primarily eat plants. Species The genus consists of two extant species: A ...
(''the star tortoises).


Extinction

The genus is highly suspected to have gone extinct due to the arrival of ''
Homo erectus ''Homo erectus'' (; meaning "upright man") is an extinct species of archaic human from the Pleistocene, with its earliest occurrence about 2 million years ago. Several human species, such as '' H. heidelbergensis'' and '' H. antecessor ...
'', 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 The Early Pleistocene is an unofficial sub-epoch in the international geologic timescale in chronostratigraphy, being the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently estimated to span the tim ...
, but persisted on
Timor Timor is an island at the southern end of Maritime Southeast Asia, in the north of the Timor Sea. The island is divided between the sovereign states of East Timor on the eastern part and Indonesia on the western part. The Indonesian part, al ...
into the
Middle Pleistocene The Chibanian, widely known by its previous designation of Middle Pleistocene, is an age in the international geologic timescale or a stage in chronostratigraphy, being a division of the Pleistocene Epoch within the ongoing Quaternary Period. T ...
.


References

{{Testudinidae Testudinidae Pleistocene turtles Miocene genus first appearances Pleistocene genus extinctions Pliocene turtles Miocene turtles Miocene reptiles of Asia Pliocene reptiles of Asia Pleistocene reptiles of Asia Prehistoric turtle genera Taxa named by Hugh Falconer Taxa named by Proby Cautley Fossil taxa described in 1837 Extinct turtles