Holotype. Madagascar. • 1 major worker; Antsiranana; Parc National Montagne d’Ambre, Mahasarika; -12.53176, 49.17662; alt. 1135 m; 17 Nov 2007; B. L. Fisher et al. leg.; montane rainforest, ex rotten log; BLF18461; CASENT0134498 (CASC). Paratype. • 1w.; same data as for holotype, CASENT0235124 (CASC).

Moderately large species. Major workers. Head in full-face view sub-oval and slightly widening posteriorly, with anterior and posterior sides slightly convex, in lateral view sub-oval; ventral and dorsal faces convex; sides of the head with dense, long, suberect to erect pilosity; medial part of frons with irregular and dense rugae, interspaces distinctly rugulate; occipital lobes, and area posterolateral from eyes without smooth notches; scape, when laid back, exceeding the midlength of head by one-fifth of its length; inner hypostomal teeth distinct, large, closely spaced, triangular, with rounded apex directed inward; outer hypostomal teeth lobe-like, wider than and approximately as high as inner teeth; inner and outer hypostomal teeth closely spaced and not connected by concavity; mesosoma rugofoveolate; gaster smooth; body ferruginous. Minor workers. Head foveolate; vertex with a few arcing, sparse, and moderately thick rugae; scape, when laid back, exceeding the posterior head margin by one-third of its length; promesonotum very low and moderately long; promesonotal groove absent; propodeal spines small, triangular; mesosoma foveolate; body yellow.

Major workers. Measurements (N = 1): HL: 1.42; HW: 1.37; SL: 0.87; EL: 0.18; WL: 1.25; PSL: 0.21; MTL: 0.87; PNW: 0.57; PTW: 0.16; PPW: 0.34; CI: 103.0; SI: 63.2; PSLI: 14.8; PPI: 47.8; PNI: 41.6; MTI: 63.2.

Head. In full-face sub-oval, widening posteriorly, with anterior and posterior sides convex (Fig. 23B). In lateral view sub-oval; ventral and dorsal faces convex; inner hypostomal teeth visible. Sides of the head with dense, long, suberect to erect pilosity; whole head with dense, long, decumbent to erect pilosity. Frons with thick, irregular, and dense rugae, interspaces distinctly rugulate. Occipital lobes with slightly thinner, dense, and irregular rugae and rugulate interspaces. Area posterolateral from eyes with dense rugoreticulae. Gena with relatively sparse and thick, longitudinal rugae with distinctly rugofoveolate interspaces. Centre of clypeus with sparse foveolae and shiny, lateral sides with indistinct rugulae; median notch present, moderately wide, and shallow; median longitudinal carina present; lateral longitudinal carinae absent. Scape, when laid back, exceeding the midlength of head by one-fifth of its length; pilosity subdecumbent to erect (Fig. 23B, D). Inner hypostomal teeth distinct, large, closely spaced, triangular, with rounded apex directed inward; outer hypostomal teeth lobe-like, wider than and approximately as high as inner teeth; inner and outer hypostomal teeth closely spaced and not connected by concavity (Fig. 63E). Mesosoma. In lateral view, promesonotum short, angular, and moderately low, posterior mesonotum moderately steep, mesonotal process indistinct, tubercle-like; promesonotal groove absent; metanotal groove absent; propodeal spines moderate, with wide base and acute apex; humeral area produced (Fig. 23D). Surface shiny and rugofoveolate. Pilosity moderately dense, long, and erect (Fig. 23D, F). Petiole. Shiny with dense foveolae; node finely foveolate, triangular, with rounded and thick apex, in rear view node dorsoventrally slightly convex; pilosity moderately sparse and erect (Fig. 23D, F). Postpetiole. Shiny and foveolate; dorsum with reduced sculpture and smooth notch; in dorsal view oval, lateral margins medially with two dentate projections; pilosity long, moderately sparse, and erect (Fig. 23D, F). Gaster. Shiny and smooth; pilosity moderately dense, long, and erect (Fig. D, F). Colour. Ferruginous with yellowish legs (Fig. 23D, F).

Minor workers. Measurements (N = 1): HL: 0.66; HW: 0.52; SL: 0.82; EL: 0.15; WL: 0.89; PSL: 0.12; MTL: 0.7; PNW: 0.36; PTW: 0.1; PPW: 0.16; CI: 128.2; SI: 158.8; PSLI: 17.4; PPI: 62.7; PNI: 69.5; MTI: 136.7.

Head. Cephalic margin slightly convex (Fig. 23A). Pilosity relatively sparse, moderately long, subdecumbent to erect. Sculpture shiny and foveolate; vertex with a few arcing, sparse, and moderately thick rugae; antennal sockets with few indistinct, curved outward rugae and foveolate interspaces. Clypeus with median longitudinal carina absent; two lateral longitudinal carinae absent. Scape, when laid back, exceeding the posterior head margin by one-third of its length; pilosity dense, subdecumbent to erect (Fig. 23A, C). Mesosoma. In lateral view, promesonotum very low and moderately long, arched; promesonotal groove absent; metanotal groove distinct; propodeal spines small, triangular (Fig. 23C). Sculpture shiny and foveolate. Pilosity very sparse, moderately long, and erect (Fig. 23C, E). Gaster. With sparse, erect pilosity (Fig. 23C, E). Colour. Yellow, legs brighter (Fig. 23C, E).

Latin for irregular in reference to strongly irregular rugae on frons of major workers.

The species was collected at 1135 m in elevation, in montane rainforest. Nest was located in a rotten log.

Pheidole anomala sp. nov. is most similar to P. veteratrix Forel, a widespread species known from Antananarivo north to Taolagnaro, and sympatric P. trichotos sp. nov. Major workers of P. anomala sp. nov. differ from both taxa in ferruginous body colouration and distinctly rugulate interspaces on frons; minor workers are easy to distinguish based on their bright yellow body colouration and entirely foveolate katepisternum.