The status of two fossils assigned to the scorpion genus Palaeophonus and its interpretation as a senior synonym of Allopalaeophonus

Palaeophonus arctus Matthew, 1895, from the late Carboniferous Fern Ledges of Nova Scotia, Canada, and Palaeophonus lightbodyi Kjellesvig-Waering, 1954, from the Silurian of Ludford Lane in England, are problematic names proposed for fossil scorpions (Arachnida: Scorpiones). Matthew's name has been widely overlooked in the literature, but features in online resources such as the Paleobiology Database, where it currently extends the stratigraphic range of the genus Palaeophonus Thorell & Lindström, 1884 from the Silurian into the Carboniferous. The fossil on which it is based cannot be interpreted with confidence as a scorpion. Kjellesvig-Waering's name is based on an isolated pedipalp chela, which lacks characters justifying its placement in Palaeophonus or any other Palaeozoic scorpion genus. Both names are treated here as nomina dubia. We also take the opportunity to synonymize Allopalaeophonus Kjellesvig-Waering, 1986 with Palaeophonus. These two mid-Silurian genera are currently placed in separate infraorders, but the holotype of Allopalaeophonus caledonicus (Hunter, 1886) is very similar in habitus to the type species of Palaeophonus: Palaeophonus nuncius Thorell & Lindström, 1884. The single character currently separating the genera, mesosomal sternite shape, is unconvincing.