Key to the O. furciceps species group

1. Bristles on elytral disc simple; dorsal surface shining, disc of pronotum barely or not at all microreticulate......................................................................... 4

– Bristles on elytral disc bifid or trifid, or lancelolate; dorsal surface dull, with distinct microreticulation............................................................................ 2

2. Lamellae of antennal club thin and elongate, much longer than in most Onthophagus species, somewhat resembling those of some Melolonthini....... .......................................................................... O. parmatus Reitter, 1892

– Lamellae of antennal club normally shaped................................................. 3

3. Relatively small species (length 4.8–8.2 mm). Pronotum equally densely punctate on disc and basally. Male: pronotum with four tubercles, the two anteromedian very closely placed and smaller than the two anterolateral; female: pronotum with an anteromedian narrow regularly convex gibbosity.... ........................................................................... O. ponticus Harold, 1883

– Relatively large species (length 5.8–9.9 mm). Pronotum densely punctate on disc, punctures gradually more spaced toward base. Male: pronotum with four equidistant tubercles, the two anteromedian more prominent than the two anterolateral; female: pronotum with an anteromedian transverse sunk gibbosity................................................................. O. psychopompus sp. n.

4. Pronotal sides obviously sinuate behind anterior angles; pronotum approximately as long as elytra...................................... O. furciceps Marseul, 1869

– Pronotal sides not sinuate behind anterior angles; pronotum longer than elytra............................................................... O. bytinskii Balthasar, 1960

In Balthasar (1963), the last taxonomic monograph covering Iranian territory, O. psychopompus sp. n. can be inserted in the key at thesis 24 (21), p. 199, to form a couplet with O. ponticus from which is easily distinguished by the characters mentioned above. Moreover, the shape of the lamella copulatrix, with the right branch, in ventral view, bifurcate, is very characteristic for the new species.