Cataulacus plebeius

A Borneo amber fossil, known from two specimens.

Identification
De Andrade and Baroni Urbani (2004) - A Cataulacus species belonging to the extant horridus group and differing from the sole representative of this group, Cataulacus horridus, in the worker, by the eyes smaller, by the teeth on the sides of the promesonotal junction broader, by the denticles on the posterior fourth of the head dorsum larger and denser.

Distribution
This taxon was described from Borneo amber.

Biology
De Andrade and Baroni Urbani (2004) - C. plebeius is very close to one of the commonest extant Cataulacus species from Borneo, C. horridus. If, on one hand, separation of the fossil from the recent species is relatively straightforward, the similarities between the two are more impressive than the differences. This comparison sharply contrasts with the one that one could make between any recent species and two other Miocene Cataulacus from Sicilian amber described by Emery (1891). Cataulacus' evolutionary speed appears to have been much lower in Borneo than in Sicily. This was to be expected if one considers the greater climatic uniformity of the tropics as compared with temperate areas. Cataulacus, moreover, is presently distributed in the Old World tropics and if its presence on Borneo is likely to be uninterrupted since Miocene, the recent species geographically closest to the Sicilian fossils today inhabit Africa south of the Sahara.

Nomenclature

 * † plebeius. †Cataulacus plebeius De Andrade & Baroni Urbani, 2004: 248, pl. 1, figs. B, C, E. BORNEO AMBER.

Worker
TL 5.16 (combined measurements of Holotype and Paratype); HL 1.16 (holotype); HW 1.34 (holotype); CI 115.5 (holotype); EL 0.38 (paratype); OI 28.3; PW 1.16 (paratype); AL 1.28 (paratype).

Vertexal crest absent. Vertexal angles prolonged into a pair of massive, triangular, broad, acute spines. Sides of the head behind eyes and outer and inner edges of the vertexal spines strongly denticulate. Mesosoma not marginate laterally, and with a distinct, massive, broad tooth on each side at the level of the promesonotal junction. Promesonotum strongly convex in profile. Propodeum much lower than the promesonotum and with a pair of very long spines, broad at the base and tapering to an acute apex. Sides of the mesosoma denticulate except on the propodeal spines. Gaster not marginate laterally.

Head minutely punctate and reticulate-rugose, the rugae more longitudinal on the frontal lobes and on the clypeus. Posterior fourth of the head dorsum with prominent tubercles raised as peaks. Dorsum of mesosoma coarsely reticulate-foveolate. Gaster strongly punctate and with thin, slightly longitudinal, irregular rugosities.

Head, mesosoma, gaster and legs with erect, truncate hairs; in addition the border of the eyes and the gastric sternites with thin, longer hairs.

Type Material
Holotype and paratype workers respectively in the two Borneo amber fragments A and B.

A single splinter of Borneo amber in the collection of Mr Jorg Wunderlich, brownish in color, rather opaque and crossed by several cracks in different directions. This splinter was subsequently cut into two and polished to separate from each other and to approach during examination two ant specimens embedded into two fragments called here:

Fragment A, 1.6 x 0.8 x 0.7 cm, containing an ant worker missing the left part of the gaster and the outer surface of the left tibiae;

Fragment B, 1.0 x 0.3 x 0.3 cm, containing one ant worker fissured in several parts and missing the upper part of the mesosoma. The head of this specimen is better visible than the one of the Fragment A but its position renders it totally inadequate for photography.

Etymology
From the Latin plebeius (Cicero ) = common, referred to the morphology of this species recapitulating the commonest traits that one would expect to find in a Cataulacus from Borneo.