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''Meiolania'' ("small roamer") is an
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
meiolaniid Meiolaniidae is an extinct family of large, probably herbivorous stem-group turtles with heavily armored heads and tails known from South America and Australasia. Though once believed to be cryptodires, they are not closely related to any living ...
stem-
turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...
native to
Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologica ...
from the
Middle Miocene The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma (million y ...
to
Late Pleistocene The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division of ...
and possibly
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
. It is best known from fossils found on
Lord Howe Island Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland P ...
, though fossils are known from mainland Australia,
New Caledonia ) , anthem = "" , image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg , map_alt = Location of New Caledonia , map_caption = Location of New Caledonia , mapsize = 290px , subdivision_type = Sovereign st ...
, and possibly Vanuatu and
Fiji Fiji ( , ,; fj, Viti, ; Fiji Hindi: फ़िजी, ''Fijī''), officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists ...
.


Taxonomy

The genus was erected in 1886 based on remains found on
Lord Howe Island Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland P ...
, which
Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils. Owe ...
assigned to the two species ''M. platyceps'' and ''M. minor'' (now a synonym of the former). These were the first good
meiolaniid Meiolaniidae is an extinct family of large, probably herbivorous stem-group turtles with heavily armored heads and tails known from South America and Australasia. Though once believed to be cryptodires, they are not closely related to any living ...
remains, and were used to show that the first known remains of a related animal, a species from
Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...
now known as '' Ninjemys oweni'' (which was assigned to ''Meiolania'' until 1992), did not belong to lizards as initially thought, but to turtles. Woodward sank ''
Niolamia argentina ''Niolamia'' is an extinct genus of South American Meiolaniidae, meiolaniid turtle. Arthur Smith Woodward classified it as being in the genus ''Meiolania'', which this genus name is an anagram of, but this was not accepted by later authors. The g ...
'' into ''Meiolania'', but this was not accepted by later authors. The species of the genus may be summarized as In
New Caledonia ) , anthem = "" , image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg , map_alt = Location of New Caledonia , map_caption = Location of New Caledonia , mapsize = 290px , subdivision_type = Sovereign st ...
, ''M. mackayi'' was described from
Walpole Island Walpole Island is an island and First Nation reserve in southwestern Ontario, Canada, on the border between Ontario and Michigan in the United States. It is located in the mouth of the St. Clair River on Lake St. Clair, about by road from Wind ...
in 1925. It was smaller and less robust than ''M. platyceps''. ''Meiolania'' remains are also known from the Pindai Caves, Grande Terre, and from
Tiga Island Tiga Island, also called Tokanod, is a small island in the South Pacific Ocean. Tiga lies from Lifou Island, and from Maré Island in the Loyalty Islands. The Loyalty Islands are part of the greater archipelago of New Caledonia. Tiga is part ...
. ''M. brevicollis'' was described in 1992 from the mid-
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 recen ...
Camfield Beds Camfield is a surname. Notable people with the surname include: * Anne Camfield (1808–1896), Australian photographer, pioneer teacher and headmistress * Bill Camfield (1929–1991), American television personality *Douglas Camfield Douglas Ga ...
of
northern Australia The unofficial geographic term Northern Australia includes those parts of Queensland and Western Australia north of latitude 26° and all of the Northern Territory. Those local government areas of Western Australia and Queensland that lie p ...
, and differed from ''M. platyceps'' in having a flatter skull and other horn proportions. A second undescribed species of ''Meiolania'' from mainland Australia is known from the Wyandotte Creek locality in Queensland, dated to the Late Pleistocene, consisting of three horn cores and a caudal vertebra, noted to be "unusually large" in size. This species is referred to as ''M. cf platyceps,'' as the remains are most similar to ''M. platyceps'' but are not diagnostic beyond genus level.
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
remains of turtles from
Vanuatu Vanuatu ( or ; ), officially the Republic of Vanuatu (french: link=no, République de Vanuatu; bi, Ripablik blong Vanuatu), is an island country located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is east of no ...
found in
Lapita culture The Lapita culture is the name given to a Neolithic Austronesian people and their material culture, who settled Island Melanesia via a seaborne migration at around 1600 to 500 BCE. They are believed to have originated from the northern Philipp ...
midden A midden (also kitchen midden or shell heap) is an old dump for domestic waste which may consist of animal bone, human excrement, botanical material, mollusc shells, potsherds, lithics (especially debitage), and other artifacts and ecofact ...
s were referred to ''Meiolania'' in 2010 as the new species ''?M. damelipi''. However, this has been disputed, with other authors stating that the remains appeared to be non-meiolaniiform, and no parietal horns, a distinctive characteristic of ''Meiolania'', have been found at any locality in Vanuatu, despite being one of the most common finds on Walpole and Lord Howe. The long bone morphology agrees more closely with a
tortoise Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a turtle shell, shell to protect from predation and other threats. The shell in tortoises is generally hard, ...
identification, a group which has otherwise not been reported from the South Pacific or Australasia. Further remains, attributable to ''?M. damelipi'' or a closely related form, have been found in various parts of the Fijian archipelago, including
Viti Levu Viti Levu (pronounced ) is the largest island in the Republic of Fiji. It is the site of the nation's capital, Suva, and home to a large majority of Fiji's population. Geology Fiji lies in a tectonically complex area between the Australian P ...
,
Vanua Levu Vanua Levu (pronounced ), formerly known as Sandalwood Island, is the second largest island of Fiji. Located to the north of the larger Viti Levu, the island has an area of and a population of 135,961 . Geology Fiji lies in a tectonically ...
, and some smaller islands. ''?M. damelipi'' is the yongest species assigned to ''Meiolania'', with the youngest remains dating to around 1000 BCE.


Description

''Meiolania'' had an unusually shaped
skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
that sported many knob-like and
horn Horn most often refers to: *Horn (acoustic), a conical or bell shaped aperture used to guide sound ** Horn (instrument), collective name for tube-shaped wind musical instruments *Horn (anatomy), a pointed, bony projection on the head of various ...
-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. The body form of ''Meiolania'' may be viewed as having converged towards those of dinosaurian ankylosaurids and xenarthran
glyptodonts Glyptodonts are an extinct subfamily of large, heavily armoured armadillos. They arose in South America around 48 million years ago and spread to southern North America after the continents became connected several million years ago. The best-k ...
. There are two species of ''Meiolania'' known from the
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
n continent: ''M. brevicollis'' and an unnamed species. The unnamed species could reach in carapace length, making it the second-largest known terrestrial turtle or tortoise, surpassed only by ''
Megalochelys atlas ''Megalochelys'' ("great turtle") is an extinct genus of cryptodiran 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 ...
'' from Asia, which lived in the Pleistocene. The smallest species in turn was ''M. mackayi'' from
New Caledonia ) , anthem = "" , image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg , map_alt = Location of New Caledonia , map_caption = Location of New Caledonia , mapsize = 290px , subdivision_type = Sovereign st ...
, with a carapace length of . Another insular species is known from
Lord Howe Island Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland P ...
, ''M. platyceps''. It was a huge turtle, about in carapace length and probably more than in total body length. Largest specimens of ''?M. damelipi'' had carapaces of long.


Behavior

''Meiolania'' is thought to have fed on plants, and they and other meiolaniids have been generally assumed to be fully terrestrial, though acceptance of this is not universal. Fossil ''Meiolania'' eggs have been reported from Lord Howe, assigned to the
oogenus Egg fossils are the fossilized remains of eggs laid by ancient animals. As evidence of the physiological processes of an animal, egg fossils are considered a type of trace fossil. Under rare circumstances a fossil egg may preserve the remains of ...
'' Testudoolithus lordhowensis.'' The eggs are large and spherical, approximately 5.4 cm in diameter, and around 800 μm thick. Like the eggs of modern turtles, they are made of
aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including prec ...
. The eggs were likely deposited within an excavated hole nest.


Extinction

It is thought that postglacial
sea level rise Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...
may have contributed to the extinction of ''M. platyceps'' on
Lord Howe Island Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland P ...
, as the area of the current island is much smaller than that exposed during the Pleistocene. They were absent when the islands were first explored by Europeans, who were likely the first humans to discover the islands. The extinction of ''Meiolania'' in mainland Australia and in Melanesia has been postulated to be due to human activity.


Gallery

Image:Meiolania platyceps.jpg, Front view of ''M. platyceps'' fossil, Lord Howe Island museum File:Meiolania platyceps AMNH 29076 cast tail.jpg, The tail of ''Meiolania platyceps'' (
AMNH The American Museum of Natural History (abbreviated as AMNH) is a natural history museum on the Upper West Side of Manhattan in New York City. In Theodore Roosevelt Park, across the street from Central Park, the museum complex comprises 26 i ...
29076) File:Meiolania platyceps (cropped).jpg, ''Meiolania platyceps'', Lord Howe Island Maritime Museum File:Meiolania platyceps AMNH 29076 cast skull.jpg, The skull of ''Meiolania platyceps'' (AMNH 29076)


See also

*
Biodiversity of New Caledonia The biodiversity of New Caledonia is of exceptional biological and paleoecological interest. It is frequently referred to as a biodiversity hotspot.Myers, Norman; Mittermeier, Russell A. ; Mittermeier, Cristina G.; da Fonseca, Gustavo A. B.; Ke ...
* Holocene extinction


References


Further reading

*


External links


''Meiolania platyceps'' Owen
(The
Australian Museum The Australian Museum is a heritage-listed museum at 1 William Street, Sydney central business district, New South Wales, Australia. It is the oldest museum in Australia,Design 5, 2016, p.1 and the fifth oldest natural history museum in the ...
; photo) {{Taxonbar, from=Q133604 Paleogene reptiles of Australia New Caledonia Holocene fauna Pleistocene reptiles of Australia Pliocene turtles Miocene turtles Meiolaniformes Miocene first appearances Holocene extinctions Neogene reptiles of Australia Quaternary reptiles of Australia Prehistoric turtle genera Taxa named by Richard Owen Fossil taxa described in 1886 Turtles of Australia Extinct turtles