(1) Megarthrus prosseni Schatzmayr, 1904
(2) Megarthrus proseni auct. (misspelling)

Important misidentifications:
(a) Megarthrus depressus auct. nec Paykull, 1789
Omalium depressum auct. nec Paykull, 1789

Nomina dubia, that possibly belong here:
(1) Omalium macropterum Gravenhorst, 1806 (nomen dubium; see note below)
Megarthrus macropterus (Gravenhorst, 1806)
(2) Megarthrus pusillus Stephens, 1834 (nomen dubium; see note below)

In works before the genus revision by Cuccodoro and Löbl (1997) this species is usually listed as Megarthrus depressus or Omalium depressum, but this was based on a misidentification and the name depressus actually refers to a different species (see Megarthrus depressus).

Note: the taxa macropterum and pusillus have been tentatively assigned to the present species by several earlier authors. However, their original descriptions are inadequate and their type material is lost, therefore Cuccodoro and Löbl (1997) regard these names as nomina dubia that cannot be identifed anymore. In addition, the name macropterum has an even more complicated taxonomic history, because several authors have also applied the name to a species in the genus Proteinus until the late 1990s/early 2000s (see Proteinus laevigatus). Since the original concept of the name Omalium macropterum cannot be corroborated anymore, it remains unclear whether the name applies to the present species, or to Proteinus laevigatus, or even to an entirely different species. I therefore fully support the notion by Cuccodoro and Löbl (1997), but I nevertheless list these two names here in the synonymy just to include and explain these names somewhere, because they have been regarded as true synonyms or even as a valid name in earlier times.