Systematic position of Triplosoba, hitherto the oldest mayfly, from Upper Carboniferous of Commentry in Central France (Insecta: Palaeodictyopterida)

A revision of the holotype of Triplosoba pulchella (Brongniart, 1883), the 'oldest mayfly', provides evidence for new attribution to Palaeodictyopterida sensu Bechly. New character states derived from the venation pattern, namely the basal connection of the median anterior with the radius and radius posterior in the forewing, the median anterior remote from the radius posterior and basally fused with the median posterior in the hindwing, and a strong costal margin formed by two connected or fused veins with a series of small spines (costa and subcosta anterior), support an ordinal placement of Triplosoba into Palaeodictyopterida (inclusive of Diphanopterodea sensu Bechly) versus Ephemeroptera as supposed by previous authors. It shares with Diaphanopterodea a potential synapomorphy in the presence of long curved connections between the three stems of the radius, media, and cubitus in the basal part of the forewing, a character not present in other groups of Palaeodictyopterida.