The skull is narrow and vaulted, with a long, sharp and slightly deflected
beak. Breadth at the squamosals 1½ times the height at basi-temporal, which
has a constricted praemaxillary ridge, and the quadrate with a very small
pneumatic foramen. The mandible is V-shaped, with a slight inflection of
the angle, and a distinct postarticular process. The symphysis is very
narrow and pointed, with a long and narrow inferior ridge, not expanding
markedly at either extremity. The sternum is longer, flatter and narrower
than in _Dinornis_, having no distinct xiphisternal notch, three costal
articulations, long and narrow costal processes, slender lateral processes
which are often elongated, and usually no coracoidal facets. The pelvis is
wider and lower than in _Dinornis_, with the lower border of the
postacetabular portion of the ilium descending as a sharp ridge much below
the level of the sacral ribs, and without any distinct pectineal process. A
hallux is present. The tibio-tarsus and tarso-metatarsus are relatively
shorter and stouter than in _Dinornis_, the latter being shorter than the
femur, which is usually stouter and relatively shorter than in
_Megalapteryx_. The length of the tarso-metatarsus is less than half that
of the tibio-tarsus. The femur, besides being usually relatively shorter is
readily distinguished from that of _Dinornis_ by its more expanded
extremities, the rather longer neck, and the much larger and ill-defined
popliteal depression.
The vertebrae are of the general type of those of _Pachyornis_, but the
anterior pneumatic foramen commences in the third dorsal. The phalangeals
are intermediate between those of _Dinornis_ and _Pachyornis_. Haast
considered that the coracoid was aborted and often absent in this genus, in
_Emeus_, and _Pachyornis_. As additional characters of the skull it may be
mentioned that there is a prominent supra-occipital protuberance, and a
depression on the squamosal above the quadrate; the par-occipital processes
are pointed, and the basi-occipital processes only slightly prominent; so
that the posterior profile of the basi-occipital is nearly straight. The
quadrate has a very short anterior process.
All the species of the genus are small, in fact _parvus_ is the smallest
but one of the family.
Type of the genus: _Anomalopteryx didiformis_ (Owen).