Aptornis defossor (AM LB544) 601651 (cropped)

The adzebills,

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

''Aptornis'', were two closely related

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

, the North Island adzebill, (''Aptornis otidiformis''), and the South Island adzebill, (''Aptornis defossor''), of the

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Aptornithidae. The family was

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...

. A fossil species, (''Aptornis proasciarostratus''), is known from the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

Saint Bathans fauna The St Bathans fauna is found in the lower Bannockburn Formation of the Manuherikia Group of Central Otago, in the South Island of New Zealand. It comprises a suite of fossilised prehistoric animals from the late Early Miocene (Altonian) period ...

Taxonomy

They have been placed in the Gruiformes but this is not entirely certain. It was also proposed to ally them with the Galloanserae. Studies of morphology and

DNA sequence DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. T ...

s place them variously close to and far off from the

kagu The kagu or cagou (''Rhynochetos jubatus'') is a crested, long-legged, and bluish-grey bird endemic to the dense mountain forests of New Caledonia. It is the only surviving member of the genus ''Rhynochetos'' and the family Rhynochetidae, alt ...

New Caledonia ) , anthem = "" , image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg , map_alt = Location of New Caledonia , map_caption = Location of New Caledonia , mapsize = 290px , subdivision_type = Sovereign st ...

, as well as the

trumpeter The trumpet is a brass instrument commonly used in classical and jazz ensembles. The trumpet group ranges from the piccolo trumpet—with the highest register in the brass family—to the bass trumpet, pitched one octave below the standard B ...

s. However, on first discovery of fossils, they were mistaken for ratites, specifically small

moa Moa are extinct giant flightless birds native to New Zealand. The term has also come to be used for chicken in many Polynesian cultures and is found in the names of many chicken recipes, such as Kale moa and Moa Samoa. Moa or MOA may also refe ...

. Its morphological closeness to the kagu may be the result of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

, although New Zealand's proximity to

and shared biological affinities (the two islands are part of the same

microcontinent Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin. Caus ...

) has led some researchers to suggest they share a common ancestor from

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final sta ...

. The Gondwanan

sunbittern The sunbittern (''Eurypyga helias'') is a bittern-like bird of tropical regions of the Americas, and the sole member of the family Eurypygidae (sometimes spelled Eurypigidae) and genus ''Eurypyga''. It is found in Central and South America, and ...

is the closest living relative of the kagu, but these are not close to the Gruiformes proper (i.e. cranes,

rail Rail or rails may refer to: Rail transport *Rail transport and related matters *Rail (rail transport) or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' ( ...

s and allies). Aptornis defossor (AM LB544) 601687

A 2011 genetic study found ''A. defossor'' to be a gruiform. There are no available DNA sequences for ''A. otidiformis'', but it was assumed the two species were more closely related to each other than to other birds. In 2019 two studies came forth with more in-depth phylogenetic methods. The first from Boast ''et al.'' (2019) using data from near-complete mitochondrial genome sequences found adzebills to be closely related to the family

Sarothruridae Sarothruridae is a family of small- to medium-sized ground-living birds found mostly in Madagascar and sub-Saharan Africa, with the genus ''Rallicula'' being restricted to New Guinea and the Moluccas. The species in this family were once consider ...

, the flufftails. Shortly after another study by Musser and Cracraft (2019), using both morphological and molecular data, found support for adzebills to be closely related to trumpeters of the family Psophiidae instead. The authors took account of Boast ''et al.'' (2019) dataset and found it took 18 more steps to support the Aptornithidae-Sarothruridae clade than for Aptornithidae-Psophiidae.

Description

The adzebills were about 80 cm in length with a weight of 18 kg, making them about the size of small

(with which they were initially confused on their discovery) with enormous downward-curving and pointed bill, and strong legs. They were flightless and had extremely reduced

wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is e ...

s, smaller than those of the

dodo The dodo (''Raphus cucullatus'') is an extinct flightless bird that was endemic to the island of Mauritius, which is east of Madagascar in the Indian Ocean. The dodo's closest genetic relative was the also-extinct Rodrigues solitaire. ...

compared to the birds' overall size, and with a uniquely reduced carpometacarpus. The two species varied mostly in size with the North Island adzebill being the smaller species; their coloration in life is not known however.

Habitat and behaviour

Their

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s have been found in the drier areas of New Zealand, and only in the lowlands. Richard Owen, who described the two species, speculated that it was an

omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nu ...

, and analysis of its bones by

stable isotope analysis Isotope analysis is the identification of isotopic signature, abundance of certain stable isotopes of chemical elements within organic and inorganic compounds. Isotopic analysis can be used to understand the flow of energy through a food web ...

supports this. Levels of enrichment in ¹³C and ¹⁵N for two specimens of ''Aptornis otidiformis'' compared with values for a moa, Finsch's duck and

insectivore A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores were ...

s like the

owlet-nightjar Owlet-nightjars are small crepuscular birds related to the nightjars and frogmouths. Most are native to New Guinea, but some species extend to Australia, the Moluccas, and New Caledonia. A flightless species from New Zealand is extinct. There i ...

s suggested that the adzebill ate species higher in the food chain than insectivores.Worthy, T. H., Richard N. Holdaway (2002):p. 212 They are thought to have fed on large

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia altho ...

tuatara Tuatara (''Sphenodon punctatus'') are reptiles endemic to New Zealand. Despite their close resemblance to lizards, they are part of a distinct lineage, the order Rhynchocephalia. The name ''tuatara'' is derived from the Māori language and m ...

s and even small

Extinction

The adzebills were never as widespread as the moa, but subjected to the same

hunting Hunting is the human activity, human practice of seeking, pursuing, capturing, or killing wildlife or feral animals. The most common reasons for humans to hunt are to harvest food (i.e. meat) and useful animal products (fur/hide (skin), hide, ...

pressure as these and other large birds by the settling

Polynesia Polynesia () "many" and νῆσος () "island"), to, Polinisia; mi, Porinihia; haw, Polenekia; fj, Polinisia; sm, Polenisia; rar, Porinetia; ty, Pōrīnetia; tvl, Polenisia; tkl, Polenihia (, ) is a subregion of Oceania, made up of ...

ns (and predation of eggs/hatchlings by accompanying

Polynesian rat The Polynesian rat, Pacific rat or little rat (''Rattus exulans''), known to the Māori as ''kiore'', is the third most widespread species of rat in the world behind the brown rat and black rat. The Polynesian rat originated in Southeast Asia, a ...

s and dogs). They became extinct before the arrival of European explorers.

References

* * * * * Worthy, Trevor H., & Holdaway, Richard N. (2002) ''The Lost World of the Moa'', Indiana University Press:Bloomington,
''North Island Adzebill. Aptornis otidiformis''.
by Paul Martinson. Artwork produced for the book ''Extinct Birds of New Zealand'', by Alan Tennyson, Te Papa Press, Wellington, 2006
''South Island Adzebill. Aptornis defossor''.
by Paul Martinson. Artwork produced for the book ''Extinct Birds of New Zealand'', by Alan Tennyson, Te Papa Press, Wellington, 2006

Footnotes

{{Taxonbar, from=Q144809 Neognathae Extinct flightless birds Extinct birds of New Zealand Higher-level bird taxa restricted to New Zealand Late Quaternary prehistoric birds Holocene extinctions Taxa named by Richard Owen Fossil taxa described in 1844 Birds described in 1844