Proceratium cavinodus

Identification
A member of the stictum clade differing from all the other species, in the worker, by the anterior face of the postpetiole anteromedially concave and weakly tumuliform laterally.

P. cavinodus is the smallest species of the stictum clade (TL = 3.29 mm instead of TL ≥ 3.5 mm for all the other species). In general morphology and sculpture it resembles the Dominican fossils Proceratium denticulatum, Proceratium gibberum and the recent Proceratium boltoni from Ghana. P. cavinodus differs from these three species mainly by the shape of the postpetiole as already stated in the diagnosis. (Baroni Urbani and de Andrade 2003)

Distribution
This taxon was described from Australia.

Nomenclature

 *  cavinodus. Proceratium cavinodus De Andrade, in Baroni Urbani & De Andrade, 2003b: 63, fig. 33 (w.) AUSTRALIA.

Worker
Head longer than broad, with subparallel sides. Vertex gently convex in full face view and flat in posterior view. Clypeus broad, subconvex, protruding anteriorly and surrounding the whole antennal insertions. Anteromedian margin of the clypeus with a superficial notch denticulate on each side; each denticle with a short, dorsal, convergent carina. Frontal carinae distant from each other, diverging posteriorly and not covering the antennal insertions. Lateral expansions of the frontal carinae very narrow and low. Genal carina present and more marked posteriorly. Frons medially concave. Gular area gently impressed. Eyes present, with only one convex facet, and placed below the mid line of the head. First funicular joint about as long as broad. Funicular joints 2-10 broader than long. Last funicular joint about as long as the sum of joints 7-10. Scapes not attaining the vertexal margin and gently thickening apically. Masticatory margin of the mandibles with 3-4 denticles before the pointed apical tooth. Palp formula 4,3.

Mesosoma as long as head length (mandibles included), gently convex in side view. Promesonotal and propodeal sutures absent. Promesopleural and mesometaplemal sutures more impressed ventrally. Basal face of the propodeum gradually sloping posteriorly. Each side between the basal and declivous faces of the propodeum with a small pointed tooth. Propodeal lobes with a small, subpointed dorsal tooth. Propodeal spiracle round and above mid height in lateral view.

Petiole about as long as broad. Petiole in dorsal view with diverging sides on the anterior third and convex on the two posterior thirds. Anterior border of the petiole concave and carinate, the carina denticulate on each side. Ventral process of the petiole corresponding to a narrow, thin, longitudinal lamella. Postpetiole broader than petiole and with subparallel sides. Anterior face of the postpetiole medially concave and laterally slightly tumuliform. Postpetiolar sternite anteromedially with a variably marked subtriangular projection. Posterior half of the postpetiolar sternite strongly convex. Constriction between postpetiole and gaster deep. Gastral tergite I strongly convex. Gastral sternite 1 not pro-jecting anteriorly. Remaining gastral tergites and sternites curved ventrally.

Legs slender, slightly elongate. All tibiae with a pectinate spur. Spurs of fore legs with a basal spine. Fore basitarsi longer than the mid ones. Hind basitarsi about 0.8 of the length of the hind tibiae. Second tarsomere of mid and hind legs longer than third and fourth tarsomeres and about as long as the pretarsus. Pretarsal claws simple. Arolium small but present.

Sculpture. Head irregularly reticulate-punctate. Mesosoma, petiole and postpetiole granulopunctate, in some parts the punctures resembling foveae and the granulation raised as peaks. First gastral tergite smooth and with dense piligerous punctures on the sides only. Legs punctate.

Body covered by hairs of three main types: (1) short, dense, suberect or subdecumbent on the whole body, erect and sparse on the funicular joints; (2) long, suberect or subdecumbent, sparse on the whole body but absent on the scapes and funicular joints; (3) shorter than hair type (1), dense and decumbent on the funicular joints only. In addition, the funicular joints bear thick, appressed, short, sparse hairs and the scapes sparse hairs shorter than hair type (2).

Colour light brown.

Measurements in mm and Indices: TL 3.29; HL 0.79; HW 0.68; EL 0.04; SL 0.54; WL 0.91; PeL 0.36; PeW 0.35; HFeL 0.62; HTiL 0.52; HBaL 0.45; LS4 0.12; LT4 0.63; CI 86.1 ; SI 68.3; IGR 0.19.

Type Material
Holotype worker (unique) labelled: "N.T. 5.vi.73, 11.59 S x 133.05 E, c. 5 km S of Tor Rock, outcrop area, R. W. Taylor, Acc. 73.434" in.

Etymology
from the Latin cavus (= concave) and nodus (= node, i. e. a generic name for petiole and postpetiole), referred to the postpetiole morphology of the species.