Dinornis Robustus
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The South Island giant moa (''Dinornis robustus'') is an extinct species of moa in the genus '' Dinornis'', known in Māori by the name moa nunui. It was one of the tallest-known bird species to walk the Earth, exceeded in weight only by the heavier but shorter extinct
elephant bird Elephant birds are extinct flightless birds belonging to the Order (biology), order Aepyornithiformes that were native to the island of Madagascar. They are thought to have gone extinct around 1000 CE, likely as a result of human activity. Eleph ...
of
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
.


Taxonomy

Moa were
ratites Ratites () are a polyphyletic group consisting of all birds within the infraclass Palaeognathae that lack keel (bird anatomy), keels and flightless bird, cannot fly. They are mostly large, long-necked, and long-legged, the exception being the Kiw ...
: large, flightless birds with a
sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...
, but lacking a
keel The keel is the bottom-most longitudinal structural element of a watercraft, important for stability. On some sailboats, it may have a fluid dynamics, hydrodynamic and counterbalancing purpose as well. The keel laying, laying of the keel is often ...
. They also had a distinctive jaw and
palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sep ...
. The origin of these birds is becoming clearer, and it is now believed that early, flighted ancestors of these birds dispersed into the Southern Hemisphere, where most flightless ratites have been found. Despite being geographically closer to the kiwi, phylogenetic analyses based on recovered DNA show moa to have been closest to the Central and South American tinamous. South island giant moa belong to the genus ''Dinornis'', and are placed within their own family, Dinornithidae, along with their close relative '' Dinornis novaezealandiae'' from the
North Island The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...
. These, along with the extinct upland moa and tinamous, are among the most basal palaeognaths. The
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
below follows a 2009 analysis by Bunce ''et al.'':


Description


Size

The South Island giant moa was the largest species of moa. Adult females stood up to tall at the back, and could reach foliage up to off the ground, making them the tallest bird species known. Despite their great height, ''Dinornis robustus'' was found to have weighed only on average, with upper estimates of around ≥ for females. Only one specimen of a complete or partially complete moa egg has been assigned to the South Island giant moa, found around
Kaikōura Kaikōura (; ) is a town on the east coast of the South Island of New Zealand, located on New Zealand State Highway 1, State Highway 1, north of Christchurch. The town has an estimated permanent resident population of as of . Kaikōura is th ...
. This egg, in length and in width, was the largest moa egg found in museum collections as of 2006.


Anatomy

Very large-bodied, they had proportionately small heads, a trait found across all ratites. Analysis of their skull shows that they had somewhat poor eyesight due to their small
orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...
, rounded bills, and a very acute sense of smell thanks to a strongly developed olfactory system. ''Dinornis'' had thinner leg bones than other moa, indicating that they were more agile, though they likely moved slowly and cautiously. Unusually, giant moas were the only large ratites that sported a hallux (the first digit of the foot). Uniquely, the moa were essentially wingless; the only remnant of a wing was the scapulocoracoid bone, which, at one point earlier in its evolution, was where the humerus should have attached.


Appearance

Giant moas were likely fully feathered, except for their heads and a small portion of the neck, as well as the tarsus and feet. Feathers belonging to this species have been found, revealing that its plumage was plain brown or slightly streaked.


Behaviour and ecology

''D. robustus,'' along with its relatives, were quite eccentric birds. Although they could reach 11+ feet in height, they mostly held their necks horizontally rather than vertically, like their distant relatives, the kiwi.


Feeding

Moa most likely filled a diurnal role in their ecosystem, similar to that of
emu The emu (; ''Dromaius novaehollandiae'') is a species of flightless bird endemism, endemic to Australia, where it is the Tallest extant birds, tallest native bird. It is the only extant taxon, extant member of the genus ''Dromaius'' and the ...
s. Because New Zealand lacked any native terrestrial, herbivorous mammals, the moa filled that niche. Giant moas in particular are ecologically equivalent to giraffes and other long-necked plant-eating
megafauna In zoology, megafauna (from Ancient Greek, Greek μέγας ''megas'' "large" and Neo-Latin ''fauna'' "animal life") are large animals. The precise definition of the term varies widely, though a common threshold is approximately , this lower en ...
, though they lack any living analogues in New Zealand. These birds sported a very robust bill, and finds of a relatively large collection of gizzard stone for grinding food indicate a highly fibrous diet. Most foraging took place in forests and open fields, with fossilized
coprolite A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name ...
s revealing the diet of ''D. robustus'' to have included
twig A twig is a thin, often short, branch of a tree or Bush (plant), bush. The buds on the twig are an important diagnostic characteristic, as are the abscission scars where the leaves have fallen away. The color, texture, and patterning of the t ...
s,
seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
s,
berries A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone fruit, stone or pit (fruit), pit although many wikt:pip#Etymology 2, pips or seeds may be p ...
,
leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...
,
flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...
s,
vine A vine is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas, or runners. The word ''vine'' can also refer to such stems or runners themselves, for instance, when used in wicker work.Jackson; Benjamin; Da ...
s,
herb Herbs are a widely distributed and widespread group of plants, excluding vegetables, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal purposes, or for fragrances. Culinary use typically distingu ...
s, and
shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...
s. It's likely that this species fed on vegetation that was unable to be digested by other species, therefore avoiding competition with other grazers. Their bill would have allowed them to feed by means of cutting and breaking twigs and stems via lateral shaking. In addition to their bills, moas had stronger neck muscles than other ratite families, which might have given them a stronger pulling / tugging force. They also could have used their necks to reach higher vegetation, if necessary.


Reproduction

Giant moas were most likely long-lived birds which took many years to reach full maturity. Similar to cassowaries, females likely would have competed for males, seeing as they were much larger. It is likely that the males would have primarily reared the chicks, as the female would have been too large to incubate the weak-shelled eggs; however, their method of incubation is still unknown. They nested in rock shelters from late spring to early summer. Chicks are speculated to have been striped, like those of other ratites.


Range

''Dinornis robustus'' lived on the
South Island The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...
of
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
as well as in Rakiura and Native Island, and its habitat was centered around the lowlands (shrubland, duneland, grassland, and forests). Along with other members of the moa family, the South Island giant moa went extinct due to predation from humans in the 15th century, about 200 years after colonisation by the Māori.


Footnotes


References


Other sources

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External links

* from
{{Taxonbar, from=Q3501588 South Island giant moa Birds of the South Island Holocene extinctions Extinct flightless birds Extinct birds of New Zealand Late Quaternary prehistoric birds Ratites South Island giant moa