Permian ancestors of Hymenoptera and Raphidioptera

The origin of Hymenoptera remains controversial. Currently accepted hypotheses consider Hymenoptera as the first side branch of Holometabola or sister-group to Mecopteroidea. In contrast, fossils confirm the idea of Martynov that Hymenoptera are related to Megaloptera and Raphidioptera. Hymenoptera have descended along with Raphidioptera from the earliest Megaloptera, the Permian Parasialidae. A related new family, minute Nanosialidae from the Permian of Russia is supposedly ancestral to Raphidioptera. The fusion of the third ovipositor valvulae is shown to be not a synapomorphy of Neuropteroidea. Parasialids and nanosialids bridge the gap between megalopterans and snakeflies; all can be classified into a single order, Panmegaloptera nom. n., including a new suborder Siarapha for Nanosialidae. The earliest megalopterans and their descendants, Raphidioptera and Hymenoptera, have passed through a “miniaturization bottleneck”, likely a common macroevolutionary mechanism.