The adzebills,

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Aptornis'', were two closely related

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

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

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Aptornithidae. The family was

endemic Endemism is the state of a species being found only 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 foun ...

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 ...

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

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

Saint Bathans fauna.

Taxonomy

Adzebills were first scientifically described in 1844 by biologist

Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomy, comparative anatomist and paleontology, palaeontologist. Owen is generally considered to have been an outstanding naturalist with a remarkabl ...

, who mistook them for a small species of moa. The first species named was '' Dinornis otidiformis'' (later ''Aptornis''), with the specific epithet referring to its similarity in size to the great bustard (''Otis tarda''). 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 sequences place them variously close to and far off from the kagu of

New Caledonia New Caledonia ( ; ) is a group of islands in the southwest Pacific Ocean, southwest of Vanuatu and east of Australia. Located from Metropolitan France, it forms a Overseas France#Sui generis collectivity, ''sui generis'' collectivity of t ...

, as well as the trumpeters. However, on first discovery of fossils, they were mistaken for ratites, specifically small moa. 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 comm ...

, although New Zealand's proximity to

and shared biological affinities (the two islands are part of the same microcontinent) has led some researchers to suggest they share a common ancestor from Gondwana. The Gondwanan sunbittern is the closest living relative of the kagu, but these are not close to the Gruiformes proper (i.e. cranes, rails and allies). 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

150px, left, ''Aptornis defossor'', Auckland Museum The adzebills were about in length with a weight of , making them about the size of small moa (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 both Lift (force), lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform (aeronautics), planform. Wing efficiency is expressed as lift-to-d ...

s, smaller than those of the

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

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 preserve ...

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, and analysis of its bones by stable isotope analysis 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 file:Common brown robberfly with prey.jpg, A Asilidae, robber fly eating a hoverfly An insectivore is a carnivore, carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the Entomophagy ...

s like the owlet-nightjars 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 animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...

tuatara The tuatara (''Sphenodon punctatus'') is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephal ...

and even small

Extinction

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

hunting Hunting is the Human activity, human practice of seeking, pursuing, capturing, and killing wildlife or feral animals. The most common reasons for humans to hunt are to obtain the animal's body for meat and useful animal products (fur/hide (sk ...

pressure as these and other large birds by the settling Māori (and predation of eggs/hatchlings by accompanying Polynesian rats and dogs). They became extinct before the arrival of European explorers. The Māori name for ''A. defossor'' was "ngutu hahau".

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 Endemic birds of New Zealand Late Quaternary prehistoric birds Holocene extinctions Taxa named by Richard Owen Fossil taxa described in 1844 Birds described in 1844