The snakefly family Mesoraphidiidae (Insecta: Raphidioptera) from the Lower Cretaceous Yixian Formation, China: systematic revision and phylogenetic implications

Mesoraphidiidae is one of the major groups among the Mesozoic Raphidioptera, with 70 described species in 30 genera. However, many mesoraphidiid taxa need to be revised and the monophyly of this family is still questionable, lacking conclusive support from convincing autapomorphies. Here, we present a systematic revision of Mesoraphidiidae from the Lower Cretaceous Yixian Formation of north-eastern China. Nine genera and 12 species are described or redescribed based on 27 fossil specimens, including four new genera and five new species, namely Allocotoraphidia gen. nov., Yixianoraphidia gen. nov., Beipiaoraphidia martynovi gen. et sp. nov., Grammoraphidia ponomarenkoi gen. et sp. nov., Proraphidia jepsoni sp. nov., Proraphidia yixianensis sp. nov. and Styporaphidia willmanni sp. nov. Two new combinations are proposed, Yixianoraphidia anomala (Ren, 1997) comb. nov. and Allocotoraphidia myrioneura (Ren, 1997) comb. nov. Proraphidia Martynova, 1947 and Styporaphidia Engel & Ren, 2008 are first recorded from the Lower Cretaceous of China. Phiradia Willmann, 1994 stat. rest. is restored as a valid genus. A preliminary phylogenetic analysis is performed to investigate the relationships among the genera of Mesoraphidiidae based on morphological data. The monophyly of the subfamily Alloraphidiinae and the tribe Nanoraphidiini, respectively, were supported in the present analysis; several genera with three forewing radial crossveins or with subradial crossveins (i.e. Cretinocellia Ponomarenko, 1988, Allocotoraphidia gen. nov., Kezuoraphidia Willmann, 1994 and Xuraphidia Hong, 1992) were assigned to earlier diverging groups in Mesoraphidiidae; however, the monophyly of Mesoraphidiinae was not recovered. The present study sheds light on the evolutionary history of Raphidioptera.