Strumigenys poinari

A Dominican amber fossil species.

Identification
Baroni Urbani & De Andrade (2007) - A member of the Strumigenys rostrata-group. Resembling Strumigenys carolinensis, but differing from it by the presence of 4 suberect hairs on the vertexal margin, by the pronotal humeral hair gently spatulate instead of long and flagellate, and by the hind basitarsi without flagellate hairs.

S. poinari resembles S. carolinensis in general habitus and mandibular dentition but the two species can be easily separate on the basis of the pilosity (see the diagnosis). S. carolinensis is known only from North and South Carolina and from Florida. Clearly Nearctic relationships are an uncommon trait among Dominican amber ants. There are no obvious relationships between S. poinari and two other Strumigenys previously described from Dominican amber (Strumigenys pilosula and Strumigenys schleeorum ). On the contrary S. poinari and the third known Dominican fossil Strumigenys, Strumigenys electrina de Andrade might belong to a unique small clade. The two species, however, differ from each other in a number of details like presence of apicoscrobal hairs (electrina only), larger size of poinari, etc.

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

Nomenclature

 * † poinari. Strumigenys poinari Baroni Urbani & De Andrade, 2007: 173, figs. 61, 62 (w.) DOMINICAN AMBER.

Worker
TL 2.15-2.20; HL 0.58-0.59; HW 0.39-0.40; SL 0.27-0.28; ML 0.13; EL 0.05; WL 0.54-0.56; CI 66.1-69.0; SI 67.5-71.8; MI 22.0-22.4.

Head strongly converging anteriorly and with round vertexal corners. Frontal lobes slightly expanded and convex. Antennal fossae ventrally with a carina visible in full-face view, straight, covering the lower margin of the scrobes and ending before the upper border of the eye. Eyes with about 5 ommatidia in the longest row, placed over the ventral margin of the antennal scrobes. With the head in profile the scrobes are distinct, with the upper and lower margins superficially marked. Lateral clypeal margins gently converging anteriorly into a convex margin. Scapes slightly compressed dorsoventrally, with sub-basal bend gently convex, slightly less than 1/2 of the head length and surpassing the eyes posteriorly. Antennae with six segments. Apical funicular joint longer than the rest of the funiculus. Mandibles short. Internal border of the mandibles with broad and triangular basal lamella followed by 12 teeth or denticles. Tooth 1 (basal) and 2 small, subequal in size, tooth 3 the longest, tooth 4 half size than 3, tooth 5 slightly shorter than 3, teeth 6 and 7 similar to 1 and 2 and followed by 4 denticles and by a small apical tooth.

Mesosoma in profile gently sloping posteriorly. A short longitudinal ruga runs on the dorsum of the pronotum and mesonotum. Propodeal teeth large, triangular and subtended by a broad lamella.

Petiole with node high and convex and with developed spongiform processes. Ventral surface of the petiole with spongiform lamina. Postpetiole convex in profile and with developed spongiform processes.

Gaster oval and with few, short costulae. Base of the first gastral tergite with broad limbus. Base of the first gastral sternite with spongiform pad.

Sculpture. Head, mesosoma and petiole reticulate-punctuate, the reticulation-punctuation larger on the head. In addition the mesonotum with sparse, very thin, longitudinal rugosities, much sparser on the mesonotum and propodeum. Mesopleurae and metapleurae largely smooth and shining. Dorsum of the postpetiole minutely punctuate and superficially shining. Gaster smooth and shining.

Pilosity. Head and mesosoma with sub decumbent or decumbent, spatulate hairs, rarer on the mesosoma. Apicoscrobal hair absent. Cephalic dorsum with 4 suberect, spatulate hairs close to the vertexal margin. Leading edge of the scapes with spatulate hairs curved basally and apically. Lateral clypeal margins with spatulate hairs curved anteriorly. Pronotal humeral hair short and slightly spatulate. Sides of the mesonotum with 1 erect, curved, thick, flagellate hair. Petiole, postpetiole and first gastral tergite with sparse, curved, thick flagellate hairs. First gastral sternites with suberect spatulate hairs.

Colour. Dark brown.

Type Material
Holotype worker in Dominican amber (GOPC No. H 10-220). Paratypes: 4 workers in the same amber piece and collection as the holotype.

Holotype and 4 paratype workers, all embedded in the same yellow amber sample 1.6 x 2.1 x 0.7 cm containing 5 workers of Strumigenys, a Diplorhoptrum worker (gaster and large part of postpetiole and right legs missing), an unidentified small insect and many debris. GOPC H 10-220. The preservation conditions of the Strumigenys specimens are good.

Etymology
This species is named after Dr. George O. Poinar, Jr. who permitted us to study this and many more interesting amber samples.