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Virtually nothing is known regarding parasites of the Dusky Darter, Percina sciera. The only parasite reported to date from this host is a piscicolid leech. Here, we report Aethycteron nigrofasciatus on the gills of this host from the Little River Drainage of the Red River System of southeastern Oklahoma. Morphometric characters of A. nigrofasciatus from P. sciera from the state conform closely to those previously reported from its only other known host, the Blackbanded Darter, Percina nigrofasciata in Mississippi. Both possess a unique curved male copulatory organ with a spine on the distal half of the shaft and a flared distal end. Aethycteron nigrofasciatus on P. sciera represents a new host record and the first geographic distributional record of this monogenean from west of the Mississippi River.