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Meiolania ("small roamer") is an extinct genus of stem-turtle[2][3] from the Middle Miocene to Late Pleistocene and possibly Holocene.

Meiolania
Temporal range: mid Miocene–Holocene
Meiolania.jpg
Cast of a Meiolania platyceps skeleton, American Museum of Natural History
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Family: Meiolaniidae
Genus: Meiolania
Owen, 1886[1]
Species
  • M. brevicollis Megirian, 1992
  • M. platyceps Owen, 1886[1]
  • M. mackayi Anderson, 1925
Synonyms
  • Miolania
  • Ceratochelys

Contents

DescriptionEdit

 
Front view of M. platyceps fossil, Lord Howe Island museum
 
The tail of Meiolania platyceps (AMNH 29076)

Meiolania had an unusually shaped skull that sported many knob-like and horn-like protrusions. Two large horns faced sideways, and would have prevented the animal fully withdrawing its head into its shell. The tail was protected by armored 'rings', and sported thorn-like spikes at the end.[4] The body form of Meiolania may be viewed as having converged towards those of dinosaurian ankylosaurids and xenarthran glyptodonts.

There are two species of Meiolania known from the Australian continent: M. brevicollis and an unnamed species. The unnamed species could reach 2 metres (6.6 ft) in carapace length, making it the second-largest known nonmarine turtle or tortoise, surpassed only by Megalochelys atlas from Asia, which lived in the Pleistocene. The smallest species in turn was M. mackayi from New Caledonia, with a carapace length of 70 centimetres (2.3 ft). Another insular species is known from Lord Howe Island, M. platyceps.

BehaviourEdit

Meiolania fed on plants. Because the remains known by 1925 were found close to beaches, it was thought to be aquatic. It is now known to have been terrestrial.

Discovery and speciesEdit

 
Comparison between the horn cores of a M. platyceps (AM F16866) and M. mackayi (holotype AM Fl7720) specimen
 
The skull of Meiolania platyceps (AMNH 29076)

The genus was erected in 1886 based on remains found on Lord Howe Island, which Richard Owen assigned to the two species M. platyceps and M. minor (now a synonym of the former).[1] These were the first good meiolaniid remains, and were used to show that the first known remains of a related animal, a species from Queensland now known as Ninjemys oweni (which was assigned to Meiolania until 1992), did not belong to lizards as initially thought, but to turtles.[5] Woodward sank Niolamia argentina into Meiolania, but this was not accepted by later authors.

In New Caledonia, M. mackayi was described from Walpole Island in 1925. It was smaller and less robust than M. platyceps.[6] Meiolania remains are also known from the Pindai Caves, Grande Terre, and from Tiga Island.[7]

M. brevicollis was described in 1992 from the mid Miocene Camfield Beds of northern Australia, and differed from M. platyceps in having a flatter skull and other horn proportions.[8]

Possible meiolaniid remains have also been found on Viti Levu, Fiji.[9]

ExtinctionEdit

It is thought that M. platyceps went extinct on the Lord Howe Island before human occupation as a result of postglacial sea level rise.[7]

See alsoEdit

ReferencesEdit

  1. ^ a b c Owen, Richard (January 1, 1886). "Description of Fossil Remains of Two Species of a Megalanian Genus (Meiolania) from "Lord Howe's Island"". Philosophical Transactions of the Royal Society. 177: 471–480. Bibcode:1886RSPT..177..471O. doi:10.1098/rstl.1886.0015.
  2. ^ Joyce, Walter G. (April 2007). "Phylogenetic relationships of Mesozoic turtles". Bulletin of the Peabody Museum of Natural History. 48: 3–102. doi:10.3374/0079-032X(2007)48[3:PROMT]2.0.CO;2.
  3. ^ Anquetin, Jérémy (2012) [9 November 2011]. "Reassessment of the phylogenetic interrelationships of basal turtles (Testudinata)". Journal of Systematic Palaeontology. 10: 3–45. doi:10.1080/14772019.2011.558928.
  4. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 67. ISBN 1-84028-152-9.
  5. ^ https://www.biodiversitylibrary.org/pdf3/005970900084521.pdf
  6. ^ Anderson, C. (1925). "Notes on the extinct Chelonian Meiolania, with a record of a new occurrence". Records of the Australian Museum. 14 (4): 223–242. doi:10.3853/j.0067-1975.14.1925.844.
  7. ^ a b White, A. W.; Worthy, T. H.; Hawkins, S.; Bedford, S.; Spriggs, M. (2010-08-16). "Megafaunal meiolaniid horned turtles survived until early human settlement in Vanuatu, Southwest Pacific". Proc. Natl. Acad. Sci. USA. 107 (35): 15512–15516. Bibcode:2010PNAS..10715512W. doi:10.1073/pnas.1005780107. PMC 2932593. PMID 20713711.
  8. ^ Megirian, D. (1992). "Meiolania brevicollissp. Nov. (Testudines: Meiolaniidae): A new horned turtle from the Australian Miocene". Alcheringa: An Australasian Journal of Palaeontology. 16 (2): 93–106. doi:10.1080/03115519208619035.
  9. ^ Worthy, T. H.; Anderson, A. J.; Molnar, R. E. (1999). "Megafaunal expression in a land without mammals-the first fossil faunas from terrestrial deposits in Fiji (Vertebrata: Amphibia, Reptilia, Aves)". Senckenbergiana biologica. 79 (2): 237–242. Retrieved 2012-03-04.

Further readingEdit

External linksEdit