Orectognathus

Bolton 2000 - What little is known of the general biology is summarised by Brown (1953). Of the 29 described species (Taylor, 1980) one, Orectognathus versicolor, has evolved worker polymorphism. Division of labour in this species has been studied by Carlin (1982) and contrasted with the worker polyethism described by Wilson (1962) in the polymorphic Daceton armigerum. Holldobler (1982) has shown that O. versicolor is also a trail-layer, a rare feature among the dacetines.

Identification
Heterick (2009) - Workers with five-segmented antenna, with the third segment much more elongate than the remaining segments of the flagellum. The mandibles are of the trap-jaw variety, long and thin.

Species by Region
Number of species within biogeographic regions, along with the total number of species for each region.

Nomenclature

 *  ORECTOGNATHUS [Myrmicinae: Dacetini]
 * Orectognathus Smith, F. 1853: 227. Type-species: Orectognathus antennatus, by monotypy.
 * Orectognathus senior synonym of Arnoldidris: Taylor, 1977: 581; Bolton, 1999: 1655; Bolton, 2000: 19.
 * ARNOLDIDRIS [junior synonym of Orectognathus]
 * Arnoldidris Brown, 1950c: 143. Type-species: Orectognathus chyzeri, by original designation.
 * Arnoldidris junior synonym of Orectognathus: Taylor, 1977: 581; Bolton, 1999: 1655.

Bolton (2000) - Workers Mandibles linear and elongate, with kinetic mode of action, each with an apical fork of 3 spiniform teeth that interlock at full closure. Mandibles at full gape open to 170 degrees or more. Basal process of mandible a curved spur; at full mandibular closure process is dorsal to labrum and fits into a mediodorsal impression on labrum. Palp formula 5, 3. Labrum roughly T-shaped, short and not capable of reflexing to conceal the labio-maxillary complex , which is permanently exposed. Each lateral labral arm locks into a deep emargination near the inner mandibular base. A single long trigger hair arises from each transverse arm of the T-shaped labrum. Eye not located ventrolaterally on side of head. Antenna with 5 segments, of which the second funicular segment (= third antennal) is an elongate bar-like fusion segment; with a weakly differentiated apical club of 2 segments. Scape, when laid back in its normal resting position, passes above the eye; apical portion of extended scape not to distinctly curved anteriorly when seen in full-face view; scape slightly downcurved near base. Scrobe absent to weakly present. Pronotal humeri and mesonotum armed or unarmed, the former more usual. Propodeal spiracle well in front of margin of declivity, at approximately the midheight of the sclerite. Metapleural gland bulla small, with its apex widely separated from the propodeal spiracle. Waist segments without spongiform tissue and without lateral laminar cuticular processes; petiole node unarmed to bidentate; postpetiolar spiracle lateral. Limbus absent from first gastral tergite; suture between first gastral tergite and sternite rounded laterobasally; basigastral costulae absent.

Baroni Urbani & De Andrade (2007) - Only one, convincing, synapomorphy is known for this genus: the hypertrophy of the second funicular joint of workers and gynes (CI 1.00, RI 0.00).