[4] 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).

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, the flufftails.

[12] 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 adzebills were about 80 centimetres (31 in) in length with a weight of 18 kilograms (40 lb), 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.

The adzebills were never as widespread as the moa but were subjected to the same hunting pressure as these and other large birds by the settling Māori (and predation of eggs/hatchlings by accompanying Polynesian rats and dogs).