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Approximately eight moa trackways, with fossilised moa footprint impressions in fluvial silts have been found throughout the North Island, including Waikanae Creek (1872), Napier (1887), Manawatu River (1895), Marton (1896), Palmerston North (1911) (see photograph to left), Rangitikei River (1939), and underwater in Lake Taupo (1973). robustus however, comprises three distinct genetic lineages and may eventually be classified as many species, as discussed above.
Analysis of the spacing of these tracks indicates walking speeds of between 3 and 5 km/h (1.75–3 mph). Therefore, the three species of Dinornis were reclassified as two species, one each formerly occurring on New Zealand's North Island (D. Examination of growth rings present in moa cortical bone has revealed that these birds were K-selected, as are many other large endemic New Zealand birds.
Because moa are a group of flightless birds with no vestiges of wing bones, questions have been raised about how they arrived in New Zealand, and from where.
There are many theories about the moa's arrival and radiation on New Zealand, but the most recent theory suggests that the moa arrived on New Zealand about 60 million years ago (Mya) and split from the "basal" (see below) moa species, Megalapteryx about 5.8 Mya instead of the 18.5 Mya split suggested by Baker et al. This does not necessarily mean there was no speciation between the arrival 60 Mya and the basal split 5.8 Mya, but the fossil record is lacking and is it most likely that early moa lineages existed but became extinct before the basal split 5.8 Mya.
The Oligocene Drowning Maximum event, which occurred about 22 Mya, when only 18% of present-day New Zealand was above sea level, is very important in the moa radiation.
Because the basal moa split occurred so recently (5.8 Mya), it was argued that ancestors of the Quaternary moa lineages could not have been present on both the South and North island remnants during the Oligocene drowning.
This does not imply that moa were previously absent from the North Island, but that only those from the South Island survived, because only the South Island was above sea level. (2009) argued that moa ancestors survived on the South Island and then recolonized the North Island about 2 My later, when the two islands rejoined after 30 My of separation. also concluded that the highly complex structure of the moa lineage was caused by the formation of the Southern Alps about 6 Mya, and the habitat fragmentation on both islands resulting from Pleistocene glacial cycles, volcanism, and landscape changes.
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.
Although dozens of species were described in the late 19th century and early 20th century, many were based on partial skeletons and turned out to be synonyms.
Currently, eleven 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.
The nine species of moa were the only wingless birds lacking even the vestigial wings which all other ratites have.
They were the dominant herbivores in New Zealand's forest, shrubland and subalpine ecosystems for thousands of years, and until the arrival of the Māori were hunted only by the Haast's eagle.
Moa extinction occurred around 1300 CE Although moa skeletons were traditionally reconstructed in an upright position to create impressive height, analysis of their vertebral articulation indicates that they probably carried their heads forward, in the manner of a kiwi.