Proceratium Species Groups

The following is based on Baroni Urbani, C., de Andrade, M.L. (2003) The ant genus Proceratium in the extant and fossil record (Hymenoptera: Formicidae). Museo Regionale di Scienze Naturali, Monografie, 36, 1–492.

Stictum Clade

 * Proceratium avium
 * Proceratium avioide
 * Proceratium boltoni
 * Proceratium gibberum
 * Proceratium deelemani
 * Proceratium denticulatum
 * Proceratium diplopyx
 * Proceratium foveolatum
 * Proceratium goliath
 * Proceratium stictum
 * Proceratium cavinodus
 * Proceratium tio

This clade corresponds to the former stictum group of Brown (1958a, 1974) originally comprising four species only: stictum, goliath, aviurn and boltoni. Another four species were added by subsequent publications: diplopyx, deelemani, denticulatum, and tio. In this paper we describe another four species belonging to the same clade: avioide, gibberum, foveolatum and cavinodus.

The members of the stictum clade share the following worker, gyne and male synapomorphy: the presence of a basal spine on the protibial spur. This character results synapomorphic for the stictum clade in our analysis but it is also present in all the members of the phylogenetically distant pergandei clade. Lattke (1990) already described this character under the name of 'seta of the protibial spur' for the fossil species denticulatum.

Five species within the stictum clade appear in a distinct group named here as goliath group: deelemani, foveolatum, goliath, stictum and tio. These species share the following synapomorphy: worker and gyne with gular area deeply concave (char. 24). They also share large, deep, irregular roveae and granulation on the head, mesosoma, petiole and postpetiole and dense, long hairs. We did not use these characters for the cladistic analysis because the sculpture is less impressed in stictum, the basal species of the goliath group and similar sculptures can be found also among members of other clades like the micrommatum and arnoldi clades. In an analogous way, a pubescence similar to that of the goliath group can be encountered in members of the micrommatum and silaceum clades.

Five of the remaining 7 species of the sfictunz clade constitute a group of species named here as avium group. This group comprises the following species: avium, avioide, gibberum, denticulatum and diplopyx. These five species share synapomorphically the antennal joints 2-10 at least as broad as long. This trait is also shared by other species of a far clade.

Two species, boltoni and cavinodus appear in an unresolved position within the clade. P. boltoni and cavinodus in general morphology resemble the fossil members of the avium group: gibberum and denticulatum. This similarity is supported by the following characters: integument reticulate-foveolate and granulate, subpetiolar process spiniform, and with the fossil denticulatum only, frontal carinae low and subparallel and clypeal notch laterally denticulate.

The 12 species of the stictum clade appear to be irregularly distributed in the tropics of the world. Goliath and tio are known respectively from Mexico and Costa Rica, gibberum and denticulatum from Dominican amber, foveolatum from Malaysia, boltoni from Ghana, cavinodus and stictum from Australia, avium and avioides from Mauritius, diplopyx from Madagascar, and deelemani from Thailand and Malaysia.

Brown (1958a, 1974) considers the shape of the clypeus, of the mandibles and of the petiole of the species of this clade as 'primitive' within the genus Proceratium. This assumption is probably based on the fact that a nodiform petiole is likely to better represent the ponerine ancestral condition than the squamiform petiole "type Sysphincta". Unfortunately there is no morphological evidence for this since the two genera closer to Proceratium have a petiole either scale-like (Bradoponera) or scale-like to weakly nodiform (Discothyrea). We are unable to define two or more clear-cut mandibular morphologies to be used as discrete characters for phylogenetic purpose within Proceratium. According to the character evolution compatible with our phylogenetic reconstruction, however, the plesiomorphic clypeal morphology for Proceratium should be either convex and protruding (like in Discothyrea and Bradoponera), or straight (like in the basal silaceum clade). The members of the stictum clade, with their notched clypeus, appear to exhibit the derived and not the plesiomorphic clypeal morphology.