Richards (1980) and other authors separated this species from P. clypealis Thomson, but recently the two species have been synonymised under P. morio. Lomholdt (1984) refers to the two as separate species and places them in a separate genus, Ceratophorus.
In discussing the two synonymised species, Falk (1991) states that P. morio occurs from southern England northwards to south Wales, south Lancashire and north-east Yorkshire, a pattern shown to largely hold true for this atlas project.
Bitsch et al. (2001) note its occurrence in north and central Europe, Turkey, Kazakhstan and Japan. Lomholdt (1984) describes its distribution in Fennoscandia as being patchy but locally frequent.