Propyrgodesmus Silvestri 1920

Genus Propyrgodesmus Silvestri, 1920

Type-species: Propyrgodesmus lobulatus Silvestri, 1920, by original designation.

Other species included: Propyrgodesmus frater Carl, 1932 and Propyrgodesmus bulbogonopus sp. nov.

Brief description. The genus shows the typical characters of the family Pyrgodesmidae with 20 body rings in both male and female. Collum dome-shaped, flabellate and tuberculate, covering the head from above, with 5+5 moderately incised rounded lobulations at a subhorizontal anterior margin. Frons and vertex clearly granulated. Antennal pit/groove deep. Antennae short, antennomere 5 being the longest and thicker than remaining antennomeres. A cerotegument crust with microvilli covering the collum and following metaterga. Body rings strongly arched dorsally, each with 2+2 longitudinal rows of 3+3 larger and fused tubercles (paramedian and dorsolateral), both rows representing bilobed tubercles most of them slightly inclined caudad, but paramedian tubercles higher than dorsolateral tubercles. Paramedian tubercle of ring 19 overhanging the body and concealing the telson (ring 20) from above. Intercalary series of grains, as well as anteromarginal and caudomarginal lobulations largely indistinguishable. Pore formula abnormal (5, 9, 12, 15, 17–19), ozopores 5, 9, 12 and 15 borne on distinct porosteles, vs 17–19 open flush on the surface. Epiproct small, directed ventrad, with terminal bristles located on ventral side. Legs short and stout, sparsely setose, with neither any adenostyles nor tarsal brushes. Gonopods fairly simple, in situ directed caudad and held parallel to each other. Coxites moderately enlarged, hemispherical and microgranulate laterally, concave medially and devoid of any spines or hairs. Telopodite simple, bipartite, branching only at about midway, characterized by the presence of structures resembling lobes or prongs.

Diagnosis. Propyrgodesmus differs from other genera of the family mainly by the abnormal pore formula (5, 9, 12, 15, 17–19) vs normal pore formula (5, 7, 9, 10, 12, 13, 15–19); the arrangement of metatergal tubercles (trilobed paramedian tubercles in combination with overhanging paramedian tubercles of the ring 19 concealing the telson); the laterally extended lobular paraterga, and the medial rather than subcaudal position of porosteles (Carl 1932).

This genus seems to be especially similar to Lobiferodesmus Silvestri, 1920 in somatic features, but shows significant differences in gonopodal structure: the presence of flattened, cylindrical telopodites, each of which is split into an acuminate main branch and a lobular medial branch, vs a unipartite and uncinate main branch which is sheathed by a lateral lamina (Silvestri 1920; Golovatch et al. 2008).