| Meiolania Temporal range: ?
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| Cast of a Meiolania platyceps skeleton, American Museum of Natural History | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Pantestudines |
| Clade: | Testudinata |
| Family: | †Meiolaniidae |
| Genus: | †Meiolania Owen, 1886 |
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Meiolania is an extinct genus of meiolaniid stem-turtle native to Australasia throughout much of the Cenozoic. Meiolania was a large turtle, with the shell alone ranging from 0.7–2 m (2 ft 4 in – 6 ft 7 in) in length. Four species are currently recognized, although the validity of two of them is disputed. Meiolania was first described as a species of lizard related to Megalania by Richard Owen towards the end of the 19th century, before the continued discovery of additional fossils solidified its placement as a kind of turtle.
The best known species is M. platyceps, known from hundreds of specimens collected in Pleistocene strata of Lord Howe Island. The oldest known species is M. brevicollis from the Miocene of mainland Australia. Other species include M. mackayi from Pleistocene New Caledonia, which may be synonymous with M. platyceps, ? M. damelipi from Holocene Vanuatu, which may represent a non-meiolaniid turtle, and the Wyandotte species, an unnamed form from Pleistocene Australia tentatively identified as M. cf. platyceps by meiolaniid researcher Eugene S. Gaffney. Additional fossil remains indicate the presence of Meiolania or a close relative in multiple localities across Australia, New Caledonia and Fiji.
Meiolania was a well-armored animal with a somewhat raised carapace with spiky edges, osteoderm-covered frontlimbs, a head adorned by massive cow-like horns and a tail encased by spiked tail rings and tipped by a large bony club. It has been hypothesized that many of these features could have been used either in self-defense or in intraspecific combat during the mating season. Furthermore, the horns could have served a role during foraging, helping the animal brush aside foliage while grazing. The discovery of fossil nests and certain adaptations against sand entering its nasal cavity indicate that they spent at least some time in arid regions or on the beaches of the islands they inhabited.
Neither the dispersal nor the extinction of Meiolania are fully understood. Several hypotheses have been proposed ranging from it spreading across the now submerged continent of Zealandia to it swimming between islands (the latter of which is now considered unlikely based on its heavy build and lack of aquatic adaptations). The extinction of this turtle was most likely a multi-facetted process with ties to climate change, reduction of its native territory by rising sea levels, predation from invasive livestock and possibly hunting by humans. However, some of the youngest records are uncertain, with the roughly 3.000 year old ?M. damelipi possibly being another type of turtle and the even younger, ca. 2.000-1.500 year old, Pindai Cave meiolaniid being indeterminate at a genus level.