This species was described based on workers collected by F. Escobar in two localities within the county of Barbacoa, Nariño province, Colombia (see localities description in Fernández and Baena, 1997): Tajadas, 1000 m (accession number 446), and Reserva Natural Río Nambí (see Escobar & Valderrama, 1995). Fernández deposited one specimen labelled as paratype from Rio Nambí at the MZSP, but in the original description, after giving information on the holotype, the authors say: “Obrera paratipo: Una obrera con los mismos datos del holotipo depositada en MZSPC; 13 obreras...”, although in the measurements section they present figures taken from 13 “ paratype ” workers. I consulted Fernández, who agreed that their intention was to consider all 14 known specimens as types, so, with their agreement, I hereby correct this information, and thus consider also the specimens from the second locality as paratypes.

The original description includes characters I used to define the Leoninus group, except for the bidentate propodeum, which is apparently the only apomorphy for this species. Megalomyrmex foreli and M. timbira may have pointed propodeal angles, but never produced as pointed teeth as in the M. bidentatus paratype examined. To the original description I should add that the paratype lacks paired pointed acrosternites at the meso and metasternae. Also Fernández & Baena (op. cit.) rightly call attention to the shape of the head, which in this sample, is greatly modified in relation to other species in this group, being much longer than broad.

The only species in the Leoninus group recorded thus far in such high Andean altitudes is M. foreli (see below), which can be distinguished from M. bidentatus by the presence of a conspicuous sharp tooth on the ventral side of the postpetiole, that may be worn out (if so leaving a noticeable scar), but never completely lacking as in M. bidentatus.