''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 t ...

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 ot ...

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" ...

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 ...

. 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 List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...

(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 subcontinent of Eurasia and it is located enti ...

) to as far east as Sulawesi 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 ...

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

, 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 Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

Archelon ''Archelon'' is an extinct marine turtle from the Late Cretaceous, and is the largest turtle ever to have been documented, with the biggest specimen measuring from head to tail and in body mass. It is known only from the Dakota Pierre Shal ...

'' and ''

Protostega ''Protostega'' ('first roof') is an extinct genus of sea turtle containing a single species, ''Protostega gigas''. Its fossil remains have been found in the Smoky Hill Chalk formation of western Kansas (''Hesperornis'' zone, dated to 83.5 mil ...

'' 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 souther ...

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 ''Titanochelon'' is an extinct genus of giant tortoises known from the Early Miocene to the beginning of the Pleistocene in Europe, extending from the Iberian Peninsula to Anatolia. Some members of the genus were larger than extant giant tortois ...

'', 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 Indian ...

), 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 s ...

.'' *''Megalochelys margae'' Early Pleistocene, Sulawesi, 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, ...

, Philippines *''Megalochelys'' sp. Middle-Late Pleistocene (about 0.8-0.12 Mya)

, 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, Indonesia

Cladistic analysis Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived ch ...

has suggested that ''Megalochelys'' closest living relative is ''

Centrochelys ''Centrochelys'' is a genus of tortoise. It contains one extant species and several extinct species: * ''Centrochelys atlantica'' * '' Centrochelys burchardi'' * ''Centrochelys marocana'' * ''Centrochelys robusta'' * ''Centrochelys vulcanica'' * ...

'' (the

African spurred tortoise The African spurred tortoise (''Centrochelys sulcata''), also called the sulcata tortoise, is a species of tortoise inhabiting the southern edge of the Sahara desert in Africa. It is the largest mainland species of tortoise in the world, and the ...

), 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 n ...

(''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, but persisted on

into the

Middle Pleistocene The Chibanian, widely known by its previous designation of Middle Pleistocene, is an Age (geology), age in the international geologic timescale or a Stage (stratigraphy), stage in chronostratigraphy, being a division of the Pleistocene Epoch withi ...

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