North Island giant moa

The North Island giant moa (Dinornis novaezealandiae) is an extinct moa in the genus Dinornis, known in Māori as kuranui. It was a large, herbivorous bird belonging to the order Dinornithiformes, and exhibited a strong sexual dimorphism, with males weighing between 55 and 88 kg and females between 78 and 249 kg. It was one of the tallest birds ever to exist, able to stretch its head to approximately 3 metres. Dinornis novaezealandiae inhabited the North Island of New Zealand, living in lowland habitats like shrublands, grasslands and forests, fulfilling a role as one of the largest terrestrial herbivores in New Zealand's ecosystem. It is believed to have been primarily herbivorous, although consumption of fungi has also been proposed. They laid large, fragile eggs which were incubated by the males, although the exact method is unknown. Along with much of the other native fauna, Dinornis novaezealandiae disappeared from New Zealand around the 15th century, roughly 200 years after the Māori first arrived on the islands. It is thought that a number of factors contributed to their extinction, the most notable being overhunting.

Taxonomy Dinornis novaezealandiae was a ratite and a member of the order Dinornithiformes. The Dinornithiformes were flightless birds that possess a sternum but lack a keel. They also had a distinctive palate. The cladogram below follows a 2009 analysis by Bunce et al.:

Origin It is believed that ratites, the flightless group of paleognaths to which Dinornis belongs, would have been able to fly. Fossil evidence points to these early flying ratites originating in the Northern Hemisphere, after which they migrated into the Southern Hemisphere and dispersed and diversified there. This migration of flying ancestors is believed to be the cause of the wide distribution of the flightless ratites across the Southern Hemisphere.

Description Dinornis novaezealandiae has been described as a bird that was "two-legged, tailless, wingless [and] clad in woolly fibres". It had "long, shaggy, hair-like feathers up to 18 cm long". Preserved feathers and skin fragments indicate that all but the legs were fully feathered and that the wings of this bird would not have been visible in life. Their feathers were brown, sometimes with pale edging.

Anatomy

Fossils of D. novaezealandiae display a large reversed sexual dimorphism where the females are much larger than males, estimated to have weighed nearly double. Using algorithms derived from data in the bones of juvenile Dinornis, an adult male has been estimated to weigh between 55 and 88 kg, whilst females have been estimated to weigh between 78 and 249 kg. Dinornis had long, slim bones compared to other moa species. The growth and development of Dinornis long bones has been found to be much slower compared to that of other ratites such as the Ostrich. The North Island brown kiwi, that does not reach adult body mass until 12 months, is viewed as a more appropriate developmental analog for the Dinornis due to the similarities that have been drawn between the time taken to reach complete maturity of hindlimbs (5 years), as well as the time upon which tarsals commence fusion with adjacent long bones (4 years). Even though it might have walked with a lowered posture, standing upright, it would have been the tallest bird ever to exist, able to stretch its head to a height of up to 3 m.

Habitat Dinornis was a widely represented genus of moa in the North Island of New Zealand, inhabiting lowland habitats like shrublands, grasslands, dunelands, and forests. The habitat of the animal is thought to have remained relatively unchanged for hundreds of thousands of years, in part due to the bird's inability to fly, although habitat shifts have been noted both during times of changing climate and vegetative zones and in reaction to the influence of anthropogenic factors such as the introduction of Polynesian rat (Rattus exulans) and Polynesian dog (Canis familiaris). Later, the human environmental impact of fires made by the Māori people also contributed to habitat alterations. Based on recent knowledge, the Kahikatea-Pukatea-tawa forest, Waikato, was home to the majority of the D. novaezealandiae population. However, bone discoveries also reveal it to have inhabited nearby areas, such as Opito, Auckland, where it was the predominant genus of moa.

Behaviour and ecology New Zealand plants and moa were in co-evolution. Moa have been found to filiramulate growth habit in plants such as divarication, heteroblasty, deciduousness, spines or spine like structures (enlarged stinging hairs), leaf loss and photosynthetic stems, mimicry and reduced visual apparency, tough and fibrous leaves, distasteful compounds and low nutrient status. Though moa ate flowers, it is unlikely that they contributed to pollination processes. On the contrary, this would have been a more destructive process than other impacts Dinornis novaezealandiae may have had on the North Island's ecology. The deep, longstanding interconnectedness between plants and moa means that the consequences of the extinction of D. novaezealandiae may still be largely unknown.

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