page_title: Moa
section_title: Evolutionary relationships
hierarchical_section_title: Moa / Evolutionary relationships
caption_attribution_description: Comparison of a kiwi (Apteryx sp., Apterygidae, Struthioniformes), ostrich (Struthio camelus, Struthionidae, Struthioniformes), and giant moa (Dinornis giganteus, Dinornithidae, Dinornithiformes), each with its egg.
context_page_description: Moa were nine species of now-extinct flightless birds endemic to New Zealand. The two largest species, Dinornis robustus and Dinornis novaezelandiae, reached about 3.6 m in height with neck outstretched, and weighed about 230 kg while the smallest, the bush moa, was around the size of a turkey. Estimates of the Moa population when Polynesians settled New Zealand circa 1280, vary between 58,000 to c. 2.5 million.
  Moa belong to the order Dinornithiformes, traditionally placed in the ratite group. However, their closest relatives have been found by genetic studies to be the flighted South American tinamous, once considered to be a sister group to ratites. The nine species of moa were the only wingless birds lacking even the vestigial wings that all other ratites have. They were the largest terrestrial animals and dominant herbivores in New Zealand's forest, shrubland, and subalpine ecosystems until the arrival of the Māori, and were hunted only by the Haast's eagle. Moa extinction occurred around 200 years after human settlement primarily due to overhunting by the Māori.
context_section_description: The moa's closest relatives are small terrestrial South American birds called the tinamous, which can fly. Previously, the kiwi, the Australian emu, and cassowary were thought to be most closely related to moa.
  Although dozens of species were described in the late 19th and early 20th centuries, many were based on partial skeletons and turned out to be synonyms. Currently, 11 species are formally recognised, although recent studies using ancient DNA recovered from bones in museum collections suggest that distinct lineages exist within some of these. One factor that has caused much confusion in moa taxonomy is the intraspecific variation of bone sizes, between glacial and interglacial periods (see Bergmann’s rule and Allen’s rule) as well as sexual dimorphism being evident in several species. Dinornis seems to have had the most pronounced sexual dimorphism, with females being up to 150%  as tall and 280% as heavy as males—so much bigger that they were formerly classified as separate species until 2003. A 2009 study showed that Euryapteryx curtus and E. gravis were synonyms. A 2010 study explained size differences among them as sexual dimorphism. A 2012 morphological study interpreted them as subspecies, instead.
  Ancient DNA analyses have determined that a number of cryptic evolutionary lineages occurred in several moa genera. These may eventually be classified as species or subspecies; Megalapteryx benhami (Archey) is synonymised with M. didinus (Owen) because the bones of both share all essential characters. Size differences can be explained by a north–south cline combined with temporal variation such that specimens were larger during the Otiran glacial period (the last ice age in New Zealand). Similar temporal size variation is known for the North Island's Pachyornis mappini. Some of the other size variation for moa species can probably be explained by similar geographic and temporal factors.
  The earliest moa remains come from the Miocene Saint Bathans Fauna. Known from multiple eggshells and hind limb elements, these represent at least two already fairly large-sized species.
caption: A comparison of a kiwi (l), ostrich (c), and Dinornis (r), each with its egg
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