Anomalopteryx: a small forest moa with a fossil diet

Anomalopteryx didiformis, the little bush moa, was a flightless plant-eater native to New Zealand. It was smaller than giant Dinornis moa and is often reconstructed at roughly 1.3 metres in an ordinary upright stance, though posture and sex affect size estimates. Its ecology is unusually well documented: bones establish anatomy and distribution; ancient DNA helps identify remains; and DNA-linked coprolites preserve evidence of leaves, shoots and ferns eaten in forest habitats. The extinct bird catalogue places it among island birds whose traces reveal more than bones alone.

Quick facts

A moa first described from New Zealand bones

Richard Owen described the species in 1844, during the first decades when moa remains became central to the study of New Zealand’s extinct birds. As researchers compared more skeletons, bones once given separate names proved to represent males, females or growth stages of the same species. Morphological and genetic studies now recognise Anomalopteryx didiformis as one of nine moa species; the genus Anomalopteryx contains this one species.

Remains occur on both the North and South Islands. They include bones and partial skeletons, with additional clues from eggshell, preserved plant matter, coprolites and DNA. The fossil range is not a map of one continuous population: suitable habitat, climate and uneven collecting all influence where remains are found.

Moa lost their wings entirely. Unlike many flightless birds, they did not retain small external wing stubs or separate wing bones. Their pelvis, hind limbs and axial skeleton support a bipedal animal with a more horizontal trunk than the upright, swan-necked pose used in some early museum mounts. The head could be raised, but a static vertical posture exaggerates the height at which the bird normally carried it.

How large was the little bush moa?

Anomalopteryx was among the smaller moa, often reconstructed at around 1.3 metres tall in a typical posture. This is not a universal maximum or a precise measurement from a complete living bird. Moa showed substantial size differences, and sex can be difficult to establish without genetic evidence. In several moa groups, females were larger than males, which led some early palaeontologists to name the sexes as different species.

The heavy-footed Pachyornis and much taller Dinornis are useful comparisons, not templates for restoring every part of the little bush moa. Differences in limb proportions, pelvis, bill and habitat indicate that moa partitioned resources rather than filling one identical ecological role. A smaller body could move among denser vegetation than the largest species.

Coprolites turn a diet hypothesis into evidence

Before food remains were linked to the species, researchers inferred diet mainly from bill shape, skeletal form and comparisons with living ratites. Coprolites are fossilised droppings that can preserve plant fragments and pollen, but they need to be attributed carefully because several birds may have lived in the same region. DNA barcoding linked some New Zealand coprolites to Anomalopteryx didiformis, supplying direct evidence about the contents of its gut.

A study of Mid-Holocene coprolites from southern New Zealand found plant material consistent with browsing in forest environments. Samples contained evidence of fibrous leaves and woody shoots, as well as fern material. Research across moa species suggests some dietary and habitat partitioning: little bush moa used forest vegetation, whereas heavier species more often fed in open habitats. The pattern is assembled from samples across sites and taxa, not one universal meal.

A coprolite is a snapshot of digestion during a limited interval. It cannot establish every seasonal food, exact annual percentages or the diet of every individual. Even with those limits, it is stronger evidence than a menu inferred only from body size or a living relative.

Ancient DNA and moa relationships

Mitochondrial DNA studies helped separate moa species and test classifications once based mainly on size. In 2025, researchers reported a draft nuclear genome for Anomalopteryx didiformis, using ancient DNA from a fossil bone found on the South Island. A nuclear genome contains many independent regions, allowing evolutionary relationships and genetic features to be compared in more detail than a short mitochondrial sequence.

This is not a recipe for bringing the species back. Ancient DNA is fragmented and chemically damaged; a draft genome is an analytical reference assembled from surviving sequences, not a perfect copy of every gene in one moa. Its value is in testing ancestry and population history alongside anatomy and archaeological evidence.

Genetic work has also clarified that some striking size differences within moa reflect sexual dimorphism. It has not erased diversity: the current framework still recognises nine species. Classification may change as more specimens and genomic data are examined.

Forest habitat and disappearance

The common name “little bush moa” reflects its association with forest settings. Coprolites and geographic distributions support browsing in vegetated habitats, while different moa species occupied a range of forest, shrubland and open-country environments. Moa lived only in New Zealand, where their large herbivorous bodies evolved without native terrestrial mammals of comparable size.

Moa disappeared after Polynesian settlement, which began in the late thirteenth century. Hunting and forest burning changed conditions in which moa populations survived, and archaeological deposits record direct interaction between people and the birds. The close timing supports a major human role, but extinction did not happen as one identical event across every island and taxon. Climate, habitat loss, population size and access to refuges also varied.

Reconstructing a living bird from remains

A reconstruction can be anchored to the leg and torso proportions, complete lack of wings and evidence for forest plant consumption. Feathers, exact colours and soft tissues are rarely preserved with bones and must be inferred from other evidence and related birds. A fern-filled forest is consistent with its ecology, but does not depict a fossilised moment.

The little bush moa combines several independent kinds of evidence. Bones describe the frame, DNA informs evolutionary relationships, and coprolites preserve actual food. Together they support a compact, wingless forest browser while leaving colour, behaviour and parts of its population history open to further study.