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Dinornithidae

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Dinornithidae

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Moa
Conservation status: Extinct (c. 1500)
Moa attacked by a Haast's Eagle
 
Moa attacked by a Haast's Eagle
Scientific classification
Kingdom: Animalia
 
Phylum: Chordata
 
Class: Aves
 
Superorder: Paleognathae
 
Order: Struthioniformes
 
Family: Dinornithidae
 
Genera
Anomalopteryx (bush moa)
Euryapteryx
Megalapteryx (upland moa)
Dinornis (giant moa)
Emeus
Pachyornis

Moa were giant flightless birds native to New Zealand. They are unique in having no wings, not even small wings, unlike other ratites. Ten species of varying sizes are known, with the largest species, the giant moa (Dinornis robustus and Dinornis novaezelandiae), reaching about 3 m (10 ft) in height and about 250 kg (550 lb) in weight. They were the dominant herbivores in the New Zealand forest ecosystem.

Contents

History

Moa are thought to have become extinct about 1500, although some reports speculate that a few stragglers of Megalapteryx didinus may have persisted in remote corners of New Zealand until the 18th and even 19th centuries.

Although it used to be thought that numbers were declining before the impact of humans, their extinction is now attributed to hunting and forest clearance by the Polynesian ancestors of the Māori, who settled in New Zealand a few hundred years earlier. Before the arrival of humans, moa were hunted by Haast's Eagle, the world's largest eagle, which is also now extinct.

Although the indigenous Māori told European settlers tales about the huge birds which they called moa, which had once roamed the flats and valleys, the widespread physical evidence that they had actually existed was never closely examined by early European settlers.

In 1839, John W. Harris, a Poverty Bay flax trader who was a natural history enthusiast, was given a piece of unusual bone by a Māori who had found it in a river bank. He showed the 15 cm fragment of bone to his uncle, John Rule, a Sydney surgeon, who sent it to Richard Owen who at that time was working at the Hunterian Museum at the Royal College of Surgeons in London. Owen became a noted biologist, anatomist and paleontologist at the British Museum.

Owen puzzled over the fragment for almost four years. He established it was part of the femur of a big animal, but it was uncharacteristically light and honeycombed.

Owen announced to a skeptical scientific community and the world that it was from a giant extinct bird like an ostrich, and named it "Dinornis". His deduction was ridiculed in some quarters but was proved correct with the subsequent discoveries of considerable quantities of moa bones throughout the land, sufficient to construct skeletons of the birds.

In July 2004, the Natural History Museum in London placed on display the moa bone fragment Owen had first examined, to celebrate 200 years since his birth, and in memory of Owen as founder of the museum.

Taxonomy

Dinornis maximus from The New Gresham Encyclopedia
Dinornis maximus from The New Gresham Encyclopedia

The kiwi were once regarded as the closest relatives of the moa, but comparisons of their DNA suggest they are more closely related to the Australian emu and cassowary. (Turvey et al., 2005).

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. More recent research, based on DNA recovered from museum collections, suggest that there were only 11-15 species, including 2-4 giant moa. The giant moa seem to have had pronounced sexual dimorphism, with females being much larger than males; so much bigger that they were formerly classified as separate species (see also below). The giant moa grew as large as 13 feet and became extinct much earlier (also by Māori hunting), about 1300.

Although traditionally reconstructed in an upright position giving impressive height, it is thought more likely that moas carried their heads forward, in the manner of a kiwi in order to graze on low-level vegetation.

Most interestingly, ancient DNA analyses have determined that there were a number of cryptic evolutionary lineages in several moa species. These may eventually be classified as species or subspecies; Megalapteryx benhami which was synonymized with M. didinus has been revealed to be a valid species by the same study (Baker et al., 2005).

Sometimes, the Dinornithidae are considered to be a full order (Dinornithiformes), in which case the subfamilies listed below would be advanced to full family status (replacing "-inae" with "-idae").

Thus, the currently recognized genera and species are:

  • Family †Dinornithidae - Moa
    • Subfamily Megalapteryginae - Megalapteryx Moa
      • Genus Megalapteryx
        • Benham's Megalapteryx, Megalapteryx benhami (South Island, New Zealand)
        • Lesser Megalapteryx, Megalapteryx didinus (South Island, New Zealand)
    • Subfamily Anomalopteryginae - Lesser Moa
      • Genus Anomalopteryx
        • Bush Moa, Anomalopteryx didiformis (South Island, New Zealand)
      • Genus Euryapteryx
        • North Island Broad-billed Moa, Euryapteryx curtus (North Island, New Zealand)
        • South Island Broad-billed Moa, Euryapteryx geranoides (South Island, New Zealand)
      • Genus Emeus
        • Eastern Moa, Emeus crassus (South Island, New Zealand)
      • Genus Pachyornis
        • Crested Moa, Pachyornis australis (South Island, New Zealand)
        • Heavy-footed Moa, Pachyornis elephantopus (South Island, New Zealand)
        • Mappin's Moa, Pachyornis mappini (North Island, New Zealand)
        • Pachyornis new lineage A (North Island, New Zealand)
        • Pachyornis new lineage B (South Island, New Zealand)
    • Subfamily Dinornithinae - Giant Moa
      • Genus Dinornis
        • North Island Giant Moa, Dinornis novaezealandiae (North Island, New Zealand)
        • South Island Giant Moa, Dinornis robustus (South Island, New Zealand)
        • Dinornis new lineage A (South Island, New Zealand)
        • Dinornis new lineage B (South Island, New Zealand)
Owen with moa skeleton
Owen with moa skeleton

Biology

It has been long suspected that the species of moa described as Euryapteryx curtus / E. exilis, Emeus huttonii / E. crassus, and Pachyornis septentrionalis / P. mappini constituted males and females, respectively. This has been confirmed by analysis for sex-specific genetic markers of DNA extracted from bone material (Huynen et al., 2003). More interestingly, the former three species of Dinornis: D. giganteus = robustus, D. novaezealandiae and D. struthioides have turned out to be males (struthioides) and females of only two species, one each formerly occurring on New Zealands North Island (D. novaezealandiae) and South Island (D. robustus) (Huynen et al., 2003; Bunce et al., 2003); robustus however, comprises 3 distinct genetic lineages and may eventually be classified as as many species as discussed above.

Moa females were larger than males, being up to 150% of the male's size and 280% of their weight. This phenomenon — reverse size dimorphism — is not uncommon amongst ratites, being most pronounced in moa and kiwis.

Claims by cryptozoologists

Though there is no reasonable doubt that moa are extinct, there has been occasional speculation that some may still exist in deepest south Westland, a rugged wilderness in the South Island of New Zealand. Cryptozoologists and others reputedly continue to search for them, but no hard evidence or actual specimens have ever been found, and their efforts are widely considered to be pseudoscientific.

Paddy Freaney's picture of what he claimed was a "moa". Even by the standards of cryptozoology, the picture quality is extremely low.
Paddy Freaney's picture of what he claimed was a "moa". Even by the standards of cryptozoology, the picture quality is extremely low.

In January 1993, on the West Coast, Paddy Freaney, Sam Waby and Rochelle Rafferty claimed to have seen a large moa-like bird. Analysis of the blurry photograph they claimed was of a moa suggested that the subject could be either a large bird or a red deer. The incident is considered a hoax, especially as Freaney is a hotelier, and may have concocted the story to attract tourists.

Moa experts say the likelihood of any moa remaining alive and unnoticed is extremely unlikely, since they would be giant birds in a region often visited by hunters and hikers. Freaney cites the rediscovery of the Takahē as evidence that living birds could still exist undiscovered. However, while the hen-sized Takahē could successfully avoid humans, a large moa would have considerably more difficulty in doing so. The Takahē was rediscovered after its tracks were identified, but no reliable evidence of moa tracks has been reported.

Trivia

  • The plural form of moa is also moa, as Māori words do not feature plural-"s".
  • In the popular MMORPG Guild Wars, moa can be tamed as combat pets.

References

  • Baker, Allan J.; Huynen, Leon J.; Haddrath, Oliver; Millar, Craig D. & Lambert, David M. (2005): Reconstructing the tempo and mode of evolution in an extinct clade of birds with ancient DNA: The giant moas of New Zealand. PNAS 102(23): 8257-8262. DOI:10.1073/pnas.0409435102 PDF fulltext Supporting Information
  • Bunce, Michael; Worthy, Trevor H.; Ford, Tom; Hoppitt, Will; Willerslev, Eske; Drummond, Alexei & Cooper, Alan (2003): Extreme reversed sexual size dimorphism in the extinct New Zealand moa Dinornis. Nature 425(6954): 172-175. DOI:10.1038/nature01871 HTML abstract Supplementary information
  • Huynen, Leon J.; Millar, Craig D.; Scofield, R. P. & Lambert, David M. (2003): Nuclear DNA sequences detect species limits in ancient moa. Nature 425(6954): 175-178. DOI:10.1038/nature01838 HTML abstract Supplementary information
  • Millener, P. R. (1982): And then there were twelve: the taxonomic status of Anomalopteryx oweni (Aves: Dinornithidae). Notornis 29: 165-170.
  • Turvey, Samuel T.; Green, Owen R. & Holdaway, Richard N. (2005): Cortical growth marks reveal extended juvenile development in New Zealand moa. Nature 435(7044): 940-943. DOI:10.1038/nature03635 HTML abstract

External links


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