Material examined— Sperchon papillosus Thor, 1901. Iran, Mazandaran Province, IR7 small stream along road to Kandelous village, 36.426388 N, 51.470001 E, 28.viii.2017 leg. Pešić, Zawal & Saboori, 2♂, 1♀ (2♂ sequenced [DCCDB072-21, IRANM001-20]). Sperchon compactilis Koenike, 1911 . Golestan Province, IR2 Kaboud-val waterfall, 36.869720 N, 54.889168 E, 26.viii.2017 leg. Pešić, Zawal & Saboori, 1♂ (sequenced [IRANM002-20], dissected and slide mounted [5. IR2 2017 G12]).
Remarks— Asadi et al. (2010) re-examined the holotype of Sperchon bispinosus Bader & Sepasgosarian, 1982 a species described by Bader & Sepasgosarian (1982) from Elburs Mountain, North Iran and placed this species into synonymy of S. papillosus Thor, 1901. Sperchon papillosus matches the original description of S. bispinosus in having integument sculpture made up of a network of fine denticles combined with additional larger papillae and the similar shape of dorsum and palp (Asadi et al. 2010).
During our 2017 survey we collected and successfully barcoded three specimens from the S. papillosus / S. compactilis -complex from North Iran. Two specimens from a small stream along the road to Kandelous village match the description of S. bispinosus / S. papillosus: integument sculpture made up of a network of fine denticles combined with additional larger papillae and P-3 with two ventral setae. One specimen from Kaboud-val waterfall lacks the ventral setae on P-3 and we assigned it to S. compactilis.
In our COI tree (Fig. 4) the sequence of the S. compactilis specimen from Iran represents a unique BIN (BOLD: AEI4363) and falls within a clade alongside the sequences from S. bispinosus specimens from Iran, which were grouped in a separate BIN (BOLD:AED2135). The examined specimens from Iran form a clade that is sister to the clade containing S. compactilis specimens (BIN BOLD:AEI4363) from the Netherlands, all nested within a clade that also includes a specimen of Sperchon papillosus from Montenegro that represent a unique BIN (BOLD: AED2134). The genetic distance between COI sequence groups (BINs) of examined specimens of S. papillosus / S. compactilis complex ranged from 1.79% K2P between Iranian specimens of S. papillosus and S. compactilis, to 5.11% K2P between S. papillosus specimen from Montenegro and specimens of S. compactilis from the Netherlands (see Table 5). Further studies integrating more markers and additional sampling is necessary to clarify the taxonomy of species of the S. papillosus / S. compactilis complex.