Thaumatomyrmex atrox

Identification
Kempf (1975) - The presence of a basal denticle on mandibles, the semicircular rugulae between frontal carinae and eyes, and the shallow, circular depression on posterior surface of petiolar node still allow for a clear-cut separation of atrox from Thaumatomyrmex ferox.

Distribution based on Regional Taxon Lists
Neotropical Region: Colombia, Costa Rica, Guyana, Panama, Venezuela.

Nomenclature

 *  atrox. Thaumatomyrmex atrox Weber, 1939a: 98, fig. 3 (w.) GUYANA. Senior synonym of manni, zeteki: Longino, 1988: 38. See also: Kempf, 1975b: 122; Brandão, Diniz & Tomotake, 1991: 339.

Worker
Kemp (1975): paratype. TL 4.4 mm; HL 0.91 mm; HW 1.09 mm; CI 120; ML 1.15 mm; MI 126; IfW 0.65 mm; IfI 60; SL 0.80 mm; SI 88; WL 1.33 mm; PnW 0.64 mm; HfL 0.97 mm; HfI 89; PW 0.73 mm. Extremely close to ferox from which it differs in the following characters:

Head slightly narrower (CI) and mandibles somewhat shorter (MI). The mandibles with a small tooth at base of proximal spine, the intermediate spine not sinuous, almost as long as one half the chord length of apical spine. Rugulae on frontal lobes prolonged caudad by curving laterad towards upper (inner) border of eyes and circumscribing the antennal socket. Greatest length of head both between anteriormost point of frontal lobes and of mandibular acetabula and the posteriormost point of occipital carina. Petiole with the anterior surface of node transversely convex, in profile almost straight (Fig. 26), apex medium rounded, posterior surface as seen from above concave, as seen from the side somewhat convex, showing on its disc a large, shallow circular depression.

Facet count across greatest diameter of eyes: 12 facets in a row. Metanotal groove present. Thorax as in ferox.

Type Material
Kemp (1975): GUIANA: junction of the Mazaruni and Cuyuni rivers, August 20, 1935, among leaves, N. A. Weber leg. 1 female (holotype, Weber collection: ). Trinidad: foothills north of Tunapuna, July 29, 1935, among leaves, N. A. Weber leg. 1 female (paratype: WWK, received from ); paratype examined.