Patagonomyrmex laevigatus

Identification
This species is uniquely characterized by the following combination of features: (1) longitudinal rugae on cephalic dorsum rarely continue to posterior margin, (2) interrugae on cephalic dorsum and dorsum of promesonotum mostly smooth and shining, (3) posterior surface of petiolar node smooth and shining, (4) inferior propodeal spines triangular, height and width similar, notably shorter than superior spines, and (5) body mostly concolorous dark brownish-black to black.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Chile.

Nomenclature

 *  laevigatus. Pogonomyrmex (Ephebomyrmex) laevigatus Santschi, 1921g: 97 (w.) CHILE.
 * Kusnezov, 1949c: 301 (m., in key).
 * Combination in Ephebomyrmex: Kusnezov, 1960b: 354.
 * Combination in Pogonomyrmex: Snelling & Hunt, 1976: 75.
 * Combination in Patagonomyrmex: Johnson & Moreau, 2016: 17.

Description
Redescription. Longitudinal rugae on cephalic dorsum prominent, weakly wavy, widely-spaced, beginning on frontal lobes but rarely extending to posterior margin; posterior margin flat in full-face view. Wavy to irregular, often discontinuous rugae arc from mandibular margins to frontal lobes and traverse longitudinally above and below eyes, usually terminating before vertex; lateral rugae weaker than those on cephalic dorsum. Interrugae on cephalic dorsum smooth and shining; vertex and posterior margin of head weakly granulate-punctate, weakly shining to smooth and shining. Dorsum of clypeus with several moderately strong, subparallel, longitudinal rugae. Mandible with six teeth; mandibular dorsum strongly rugose. MOD ranging from 0.20–0.25x HL. In profile, eyes situated anterior to middle of head, OMD = 0.76–0.93x MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes long (SI = 84.07–97.94), surpassing vertex by less than length of second funicular segment; scapes weakly to moderately granulate-punctate, often with faint striae, weakly shining; basal flange moderately well-developed with carinate margin. Mesosomal profile strongly convex; dorsum of promesonotum smooth and shining; longitudinal rugae on mesospleura and metapleura wavy to irregular, interrugae weakly to moderately granulate-punctate, weakly shining. Promesonotal suture absent to weakly impressed on occasional individuals. Superior propodeal spines long, narrowing to blunt tip, length rarely >0.7–0.8x the distance between their bases; inferior propodeal spines moderately well-developed, triangular, acuminate, length and width similar, distinctly shorter than superior spines. Propodeal spiracles weakly ovate to circular facing posterad. Legs weakly granulate, weakly shining to smooth and shining. Peduncle of petiole about as long as petiolar node, anteroventral margin of peduncle of petiole with a small, acuminate spine. In profile, posterior surface of petiolar node weakly convex; petiolar node asymmetrical with anterior surface shorter than posterior surface, apex bluntly angulate to rounded. In dorsal view, petiolar node longer than wide, sides subparallel, narrowing to rounded to bluntly angulate anterior margin. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing to anterior margin, maximum width and length similar; posterior surface and sides of petiolar node and dorsum and sides of postpetiole smooth and shining; first gastral tergum smooth and shining. Erect, short to long, copperish-brown hairs abundant on head, one to few approaching to slightly exceeding MOD. Moderately abundant subdecumbent to decumbent hairs on antennal scapes; abundant decumbent to appressed hairs on funicular segments. Legs with moderately abundant subdecumbent to decumbent setae. Mesosoma with moderately dense, medium to long, erect setae, longest approaching MOD; petiolar node, postpetiole, gastral terga with moderately dense, erect setae, mostly similar in length, longest notably shorter than MOD. Body mostly concolorous dark brownish-black to black.