Typhlomyrmex lenis

The only known specimen of this species was collected in an area at the southern distribution of Atlantic Forest, one of the most biodiverse biomes in the world. Since the specimen was collected during an expedition focused on the forest areas of the biome, it was likely collected in this vegetation type.

Identification
Camacho et al. (2020) - Size comparatively small (TL 3.61). Dorsal surface of mandible smooth and shiny. Eye with a single ommatidium. Scape, legs and gaster yellow, much lighter than the rest of the body. Dorsal profile of mesosoma flat, with a shallow metanotal impression. Propodeal spiracle with wide opening, turned slightly posteriorly and at the same level of integument. Propodeum with lobes on the angle of contact between the dorsal and declivitous faces, in lateral view. Declivitous face of propodeum with some poorly marked rugulae. Metacoxal spine absent. Segments I and II of gaster completely smooth and shiny, without striae forming from the base of the hairs; anterior face of the gaster smooth and hairless.

Anterior and posterior margins of petiole subparallel in lateral view; petiole not pedunculated. Subpetiolar process predominantly opaque and subquadrate, very large, occupying more than half of the ventral surface of the petiole; subpetiolar process with a fenestra next to its posterior limit. In dorsal view, the first gastral segment trapezoidal, and the angles of its anterior margin rounded but differentiated. Prora reduced.

Although G. lenis is known from a single specimen, it can be clearly distinguished from its closest relatives, Gnamptogenys lavra and Gnamptogenys reichenspergeri. Gnamptogenys lenis has completely smooth and shiny mandible and gaster (shortly striate in G. lavra and G. reichenspergeri), and the scape surpasses the vertex margin (barely reaching the vertex margin in the other two species).

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Known only from the type locality, Seara, Santa Catarina, Brazil.

Nomenclature

 * . Gnamptogenys lenis Camacho, et al. 2020: 470, fig. 21 (w.) BRAZIL (Santa Catarina).
 * Type-material: holotype worker.
 * Type-locality: Brazil: Santa Catarina, Seara, 24°07’S, 52°18’W, 6.vii.1999 (R.R. Silva).
 * Type-depository: MZSP.
 * Distribution: Brazil.

Worker
Worker: HL 0.80; HW 0.71; ML 0.45; SL 0.61; EL 0.06; WL 1.04; PL 0.29; GL 1.01; TL 3.61; CI 86.36; SI 85.96; OI 8.77 (n=1).

Small size. Body brown-coppery, with appendages and gaster lighter, coppery to yellowish. Body predominantly covered by thin, long, decumbent to suberect hairs.

Mandible smooth and shiny, without rugulae or striations on the dorsal surface. Head dorsum covered by long longitudinal costulae, deep and slightly irregular, semiparallel from the anterior margin of clypeus to the vertex margin; vertex with rugulae and inconspicuous striae and 10 to 12 hairs aligned transversely and directed above; surface of costulae covered by punctuation, giving them a rough appearance; intervals between costulae smooth and shiny. Mesosoma completely covered by narrow costulae, approximately 0.025 mm in width and slightly irregular margins on the dorsal surface; pronotum with transverse costulae anteriorly and several subparallel costulae on the dorsal surface. Declivitous face of propodeum smooth and shiny, with only a few lightly marked rugulae crosscutting at the base of the slope. Coxae always covered by transverse costulae; in procoxa, costulae narrower than those on the rest of the body. Petiole with different sculpture from mesosoma, smooth and shiny, with inconspicuous rugulae on the dorsal and lateral surfaces. Segments I and II of gaster smooth and shiny; posterior margin of gastral tergite I with a leathery pattern centrally. Anterior face of the first gastral segment bare; dorsal surface of gaster without rugulae or striae.

Mandible triangular and massive. Anterior margin of clypeus strongly convex, and clypeal lamellae strongly projected centrally, giving it a triangular appearance in frontal view. Lateral margins of head straight and subparallel, slightly tapered anteriorly. Occipital corners extend ventrally, forming two longitudinal keels that do not reach the median suture of the ventral surface of the head. Antennal scape narrow, almost twice as wide apically as at its base; scape slightly surpassing the vertex margin. Eye with a single ommatidium, located slightly behind the anterior half of the head in frontal view. Vertex margin strongly concave medially, giving vertex corners a heavily angled aspect.

Dorsal profile of mesosoma compact and flat in lateral view, with a light mesonotal impression. Dorsal surface of mesonotum, metanotum and propodeum with semiparallel and longitudinal costulae. Lateral margins of declivitous face of propodeum parallel; dorsal and declivitous face of propodeum undifferentiated, without a carina between the two; propodeal spiracle at the same level as the integument; propodeal spiracle with very wide opening. Propodeum with small lobes projecting from the angle formed between the dorsal and declivitous faces. Metacoxal projection absent.

Etymology
From Latin lenis=smooth, in reference to the species smooth and shiny gaster, a characteristic that is key to distinguishing Gnamptogenys lenis from its closely related species, Gnamptogenys lavra. The species name is a feminine adjective in the nominative singular.