Oldest winged insects: first Megasecoptera from the early Carboniferous (Serpukhovian) of Argentina

Mississippian insect records are extremely rare. Formally, winged insects occur only at two sites from the Serpukhovian: Delitzsch in Germany, with one species of Palaeodictyoptera; and Guandacol 1 in Argentina, comprising three species from three different dragonfly orders: Eugeroptera, Kukaloptera and Argentinoptera. Herein we describe a new species of Xenopteraidae: Xenoptera latigra sp. nov. from Guandacol 1 Formation in La Rioja province, which represents the oldest Megasecoptera (absolute dating of 326 Ma). Palaeoptera insects from the Carboniferous are also present in La Cuestita de la Herradura locality from Malanzán Formation, in the same basin and 240 km distant from Guandacol 1. Although the latter lacks absolute dating, the fact that both localities share taxa such as the Eugeropteridae and the genus Xenoptera , suggests lateral equivalence and similar palaeoenvironmental conditions. In conclusion, we have the oldest entomofauna of Pterygota recorded worldwide, representing the oldest continental aquatic deposits with terrestrial adults of Megasecoptera and Odonatoptera. This also allowed us to infer the presence of demic immature insects, the aquatic ‘nymphs’ of the basal odonatopterans. The correlation of Guandacol 1 with La Cuestita de la Herradura results in seven species from six genera, five families and five orders of Palaeoptera.