Cylindromyrmex electrinus

A Dominican amber fossil species known only from the queen caste.

Identification
De Andrade (1998) - A species appearing in an unresolved position together with Cylindromyrmex brevitarsus and Cylindromyrmex darlingtoni within the brevitarsus clade, but differing from both other species by the following combination of characters: basal face of the propodeum separated from the declivous one by a marked margin, by the coxae and femora black instead of dark brown, and by the mid basitari long and not broad distally.

C. electrinus, in the phylogeny proposed in this paper, appears close to the recent brevitarsus and darlingtoni. These three species differs from the basalmost species of the clade, Cylindromyrmex escobari, by the presence of striae on the first gastric tergite. C. electrinus shares with brevitarsus the frontal carinae reaching the anterior border of the clypeus and the mandibles with 6-7 denticles, and with darlingtoni the striae on the first gastric tergite thin, short and restricted on the anterior part only. C. electrinus is very similar to both brevitarsus and darlingtoni, but the characters listed above allow an easy separation of the fossil from both recent species.

Distribution
This taxon was described from Dominican Amber (Miocene).

Nomenclature

 * † electrinus. †Cylindromyrmex electrinus De Andrade, 1998a: 619, figs. 2, 18 (q.) DOMINICAN AMBER (Miocene).

Queen
TL 7.36; HL 1.24; HW 0.94; EL 0.36; SL 0.46; SW 0.16; WL 2.20; PeL 0.68; PeW 0.56; HFeL 0.75; HFeW 0.30; HTiL 0.64; HTiW 0.21; HBaL 0.47; HBaW 0.08; CI 75.8: SI 36.9; HFeI 40.0; HTil 32.8; HBal 17.0.

Head ca. 1/4 longer than broad, with parallel sides. Occiput high. Vertexal angles convex. Frontal carinae about half broad as the maximum head width. Anterior third of the frontal carinae diverging backwards. Dorsum of the frontal carinae with an impressed, median sulcus anteriorly. Frontal carinae reaching the anterior border of the clypeus. Compound eyes large, slightly flat and mostly on the posterior half of the head. Ocelli well developed. Scapes reaching the anterior border of the eyes. Proximal third of the scapes about 1/2 narrower than the remaining parts. Mandibles convex dorsally. Masticatory margin of the mandibles with a set of 6-7 irregular denticles followed by a pointed apical one.

Mesosoma dorsally flat and ca. 1.3 longer than the length (mandible included). Pronotum dorsally with the sides superficially marginate. Propleurae gently concave. Mesopleurae gently convex. Propodeum with the sides converging posteriorly. Basal and declivous faces of the propodeum subequal in size and delimited by a margin.

Petiole ca. l /4 longer than broad, anteriorly truncate and the dorsally convex. Ventral process of the petiole triangular. Postpetiole diverging backwards and broader posteriorly. Anterior corners of the postpetiole angulate. Postpetiole in dorsal view antero-laterally angulate. Postpetiolar sternite antero-medially with a salient, triangular “lip” pointing backwards. Pygidium obliquely truncate: its sides bearing many irregularly distributed mall denticles converging to 4 small teeth over the sung.

Legs. Femora slightly inflated. Mid basitarsi with parallel sides. Hind basitarsi slightly less than 1/3 shorter than the length of the hind tibiae. Mid basitarsi ca. 1/2 of the length of the hind basitarsi. Outer apical edge of the hind and of the mid basitarsi respectively with 4,5 pine-like setae.

Sculpture. Head covered by thin, longitudinal striae, thicker on the posterior part of the dorsum, thinner close to the antennal scrobes, absent on the posterior third of the ventral part of the head. Posterior third of the ventral part of the head minutely punctate and smooth. Dorsum of the pronotum with at least 40 striae similar to those on the posterior pan of the head dorsum. Mesonotum with at least 25 striae thinner than those on the pronotum. Scutellum covered by striae lightly thinner than those on the mesonotum. Dorsum of the propodeum covered by striae similar to those on the mesonotum. Pleurae and petiole with longitudinal striae similar to those on the scutellum, the striae more superficial on the upper mesopleurae and on the sides of the petiole. Petiolar dorsum with at least 25 striae. Postpetiole covered by at least 50 striae similar to those on the mesonotum. First gastric tergite with very thin, short striae on the center of the anterior half only. Remaining gastric tergites and sternites smooth and with variably impressed punctuations more impressed on the last segments. Legs with very superficial, minute puncture. Hind coxae with thin, longitudinal striae.

Pilosity. Body with pointed hairs of at least three lengths and distributed as follows: (1) long, erect to suberect, one on the external border of the scape, a pair between the frontal carinae and the clypeus, rare on the external border of the mandibles, rare on the gaster, sparse on the pygidium; (2) shorter than the type (1) and sparsely distributed on the whole body; (3) shorter than the type (2), erect to suberect, sparse on the whole body. In addition. the hypostomal bridge surrounded by a layer of hairs similar to the type (1).

Colour black. Tibiae of three pairs of legs partially yellowish and transparent or dar k brown. Tarsi dark brown, tarsomeres lighter.

Type Material
Holotype: Winged gyne in an amber sample without reference number from.

Etymology
From the Latin electrinus (= made of amber).