Megalapteryx: New Zealand’s upland moa

Megalapteryx didinus, the upland moa, was a flightless bird of New Zealand’s South Island and one of the smaller moa species. Its common name reflects frequent finds in mountain and subalpine settings, although bones also come from lower forests. Dry, cold caves preserved skin, muscles and feathers as well as skeletons. DNA has identified both eggshell and coprolites, and plant remains in the droppings show a broad herbivorous diet. The extinct bird catalogue includes Megalapteryx among the birds whose fossils preserve unusually direct traces of life.

Quick facts

A moa known from bones and mummies

Richard Owen described the species in 1883 as Dinornis didinus, using a remarkable dried specimen found near Queenstown in 1878. Its type material, Natural History Museum specimen PV A 16, includes mummified parts of the head, neck and hind limbs. Julius von Haast later erected Megalapteryx for a form he named M. hectori; subsequent study showed that name referred to the same species. The genus is now represented by M. didinus.

Other names accumulated as paleontologists encountered bones of different sizes and from separate districts. In 1941, the larger northern material was named M. benhami. T. H. Worthy’s 1988 review compared skulls, sterna, pelvises, shoulder bones and the main leg elements. He found no stable difference in bone shape: large and small individuals fell within a continuous size range. The larger northwestern Nelson sample also came mainly from glacial-age deposits, whereas smaller birds occurred in both glacial and Holocene layers. Worthy therefore treated M. benhami as a synonym of M. didinus.

Genetic studies have found substantial mitochondrial variation among moa populations. Deep genetic splits alone do not establish separate species when a clear morphological boundary is absent. In this case, the current single-species treatment reflects the combined evidence rather than a claim that all populations were genetically identical.

Size and the skeleton

Megalapteryx was more lightly built than the heavy-footed moa Pachyornis, but it was still a substantial bird. Its skull had a narrow, pointed front to the beak, relatively small temporal openings and a comparatively slender bill. The pelvis was narrow, the femur elongated, and the tarsometatarsus relatively short. Like all moa, it lacked functional wings and relied on its powerful hind limbs for movement.

Measurements vary among samples. In one large Takahe Valley sample, mean femur length was 220.6 millimetres, mean tibiotarsus 322.8 millimetres and mean tarsometatarsus 150.7 millimetres. Means from northern cave samples at Mount Owen and Honeycomb Hill were larger: femora about 246–264 millimetres, tibiotarsi 389–410 millimetres and tarsometatarsi 172–186 millimetres. Those differences help explain the old two-species hypothesis, but they do not by themselves demonstrate two contemporaneous species.

Adult mass is usually estimated at roughly 20–50 kilograms from skeletal size and comparison with living birds. It is not a measurement from a complete fresh body, and one value cannot describe every adult. Age, sex, locality and climatic interval may all contribute to variation in the fossil sample.

What the mummies preserve

Some South Island caves combined low temperatures with very dry air. Tissue could desiccate before it decomposed, preserving skin, tendons, muscles, feather bases and individual feathers. A study of a mummified head and neck traced nine skull muscles after carefully rehydrating the tissue. The preserved anatomy included much of the jaw musculature, the eyelid’s orbicular muscle and a temporal skin muscle. Researchers also examined collagen and degraded DNA. Details of the inner-ear stirrup differed from kiwi and shared features with emu, adding a further anatomical comparison.

A mummified foot preserves feathers reaching down toward the ankle. This is direct evidence of feather placement and has been interpreted as insulation in a cool upland setting. It does not show whether feather density changed seasonally or how the bird regulated heat. Nor can the brown or greenish hues of dried tissue be read straightforwardly as the live plumage: pigments and feather structure alter after death.

Ancient DNA from eggshell has identified olive-green shell as belonging to Megalapteryx. That result links an egg to the species, but shell colour says nothing about the adult’s feather pattern. Exact colour, display and vocalisation remain beyond the evidence.

A lineage of its own

Morphological and molecular analyses place Megalapteryx in the distinct family Megalapterygidae, an early-diverging branch among moa. It was not simply a small version of Emeus or Anomalopteryx, whose size could be similar but whose family relationships differed. A separate branch does not mean that every anatomical feature was primitive; the narrow pelvis, bill and upland distribution reflect its own evolutionary history.

One molecular analysis associated the separation of the Megalapteryx lineage with late Miocene geological change and uplift in the Southern Alps. The timing is compatible with growing relief fragmenting habitats and populations, but it cannot show that a single episode of uplift caused the lineage to originate. The geological and genetic dates carry uncertainty, and correlation is not a direct record of the process.

Fossils occur in northwestern Nelson caves, Central Otago, Fiordland and other South Island districts. The bird is often associated with montane or subalpine environments, yet lowland forest deposits also contain its bones. “Upland moa” is a useful common name, not proof that every individual remained above the tree line throughout the year.

Diet from 35 coprolites

At Euphrates Cave, near the forest limit, researchers studied 35 well-preserved coprolites. Ancient DNA identified them as droppings of M. didinus. Twelve were radiocarbon dated, with measurements spanning 6,368 ± 31 to 694 ± 30 radiocarbon years before present. The dates show repeated deposition over millennia rather than one brief visit by a single bird.

Combining pollen, plant macrofossils and plant DNA, the study identified at least 67 plant taxa. The remains include southern beech, grasses, sedges, herbs and shrubs, along with nectar-rich flowers of New Zealand flax and tree fuchsia. The assemblage indicates flexible feeding, including browsing woody growth and grazing lower vegetation across forest, shrubland and grassland habitats.

Many intact seeds occur in the droppings, so the moa may have dispersed some plants. The study did not test whether those particular seeds would germinate. Small invertebrate fragments are not enough to make the bird an omnivore; they could have been swallowed accidentally with vegetation or entered a sample after deposition.

Eggs, people and extinction

Eggshell DNA securely connects some olive-green shell to the upland moa. The number of eggs in a nest, incubation period and which parent incubated them are not directly known for this species. General findings about moa reproduction should not automatically be treated as observations of Megalapteryx.

Genetic work did not find a prolonged loss of diversity immediately before the species disappeared. This offers no support for the idea that a long demographic collapse had already doomed it before people arrived, although it cannot exclude every ecological stress. Moa vanished after Polynesian settlement of New Zealand in the late thirteenth century. Archaeological evidence, rapid loss across the group and models of harvesting point to hunting as a major pressure; burning and other habitat changes also altered the island’s ecosystems.

It is not possible to assign the fate of one Megalapteryx individual to a single cause. The last dated bone is not automatically the date of the last living bird, and stories of much later survival lack securely dated remains. What the record supports is a flightless herbivore that persisted through changing climates and disappeared during the profound ecological transformation following human settlement.