Meiolania
Encyclopedia
Meiolania is an extinct genus
of cryptodire
turtle
from the Oligocene
to Holocene
, with the last relict
populations at New Caledonia
which survived until 2,000 years ago.
The animal was rather large, measuring 2.5 metres (8.2 ft) in length, making it the second-largest known nonmarine turtle or tortoise
, surpassed only by Colossochelys atlas from Asia, which lived in the Pleistocene. It lived in Australia
and New Caledonia
. Remains have also been found on the island of Efate
in Vanuatu
, associated with settlements from the Lapita
culture. Meiolani turtles fed on plants. Its surviving relatives are the cryptodire
turtles of South America
. The Meiolania specimens which were once living on New Caledonia and Lord Howe Island
were much smaller than their giant relatives from the Australian continent.
When the first fossil remains (a vertebra) were found, they were originally thought to be from a large monitor lizard
, similar to, but smaller than Megalania
, so the genus was named accordingly. Later, when more remains were found, it was realized that the "small roamer" was actually a turtle, and not a lizard. Synonyms include Miolania and Ceratochelys.
Meiolania had an unusually shaped skull
that sported many knob-like and horn
-like protrusions. Two large horns faced sideways, giving the skull a total width of 60 centimetres (2 ft), 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
.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of cryptodire
Cryptodira
Cryptodira is the taxonomic suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira in that they lower their necks and pull the heads straight back into the shells; instead of folding their necks sideways along the body under the shells' margins...
turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
from the Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
to Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
, with the last relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....
populations at New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
which survived until 2,000 years ago.
The animal was rather large, measuring 2.5 metres (8.2 ft) in length, making it the second-largest known nonmarine turtle or tortoise
Giant tortoise
Giant tortoises are characteristic reptiles of certain tropical islands. Often reaching enormous size—they can weigh as much as 300 kg and can grow to be 1.3 m long—they live, or lived , in the Seychelles, the Mascarenes and the Galapagos...
, surpassed only by Colossochelys atlas from Asia, which lived in the Pleistocene. It lived in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
. Remains have also been found on the island of Efate
Éfaté
Efate is an island in the Agean Ocean which is part of the Shefa Province in The Republic of Maliki. It is also known as Île Vate. It is the most populous island in Vanuatu. Efate's land area of makes it Vanuatu's third largest island. Most inhabitants of Efate live in Port Vila, the national...
in Vanuatu
Vanuatu
Vanuatu , officially the Republic of Vanuatu , is an island nation located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is some east of northern Australia, northeast of New Caledonia, west of Fiji, and southeast of the Solomon Islands, near New Guinea.Vanuatu was...
, associated with settlements from the Lapita
Lapita
Lapita is a term applied to an ancient Pacific Ocean archaeological culture which is believed by many archaeologists to be the common ancestor of several cultures in Polynesia, Micronesia, and some coastal areas of Melanesia...
culture. Meiolani turtles fed on plants. Its surviving relatives are the cryptodire
Cryptodira
Cryptodira is the taxonomic suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira in that they lower their necks and pull the heads straight back into the shells; instead of folding their necks sideways along the body under the shells' margins...
turtles of South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. The Meiolania specimens which were once living on New Caledonia and Lord Howe Island
Lord Howe Island
Lord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...
were much smaller than their giant relatives from the Australian continent.
When the first fossil remains (a vertebra) were found, they were originally thought to be from a large monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...
, similar to, but smaller than Megalania
Megalania
Megalania is a giant extinct goanna or monitor lizard. It was part of a megafaunal assemblage that inhabited southern Australia during the Pleistocene, and appears to have disappeared around 40,000 years ago...
, so the genus was named accordingly. Later, when more remains were found, it was realized that the "small roamer" was actually a turtle, and not a lizard. Synonyms include Miolania and Ceratochelys.
Anatomy
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
that sported many knob-like and horn
Horn (anatomy)
A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...
-like protrusions. Two large horns faced sideways, giving the skull a total width of 60 centimetres (2 ft), 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
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
towards those of dinosaurian ankylosaurids
Ankylosauridae
An ankylosaurid is a member of the Ankylosauridae family of armored dinosaurs that evolved 125 million years ago and became extinct 65 million years ago during the Cretaceous-Tertiary extinction event...
and xenarthran glyptodonts
Glyptodontidae
Glyptodonts were large, more heavily armored relatives of extinct pampatheres and modern armadillos.They first evolved during the Miocene in South America, which remained their center of species diversity...
.
See also
- Biodiversity of New CaledoniaBiodiversity of New CaledoniaThe Biodiversity of New Caledonia is considered to be one of the most important in the world. New Caledonia, a large south Pacific island group about 1,200 km east of Australia, supports high levels of endemism, with many unique plants, insects, reptiles and birds...
- Holocene extinction
External links
- Meiolania platyceps Owen (The Australian MuseumAustralian MuseumThe Australian Museum is the oldest museum in Australia, with an international reputation in the fields of natural history and anthropology. It features collections of vertebrate and invertebrate zoology, as well as mineralogy, palaeontology, and anthropology...
; photo) - Mikko's Phylogeny ArchiveMikko's Phylogeny ArchiveMikko's Phylogeny Archive is an amateur paleontology website maintained by Mikko Haaramo, a student at the University of Helsinki's Department of Geology, Division of Geology and Palaeontology....
on Cryptodira