What is "choristotanyderus"

Choristotanyderus is an extinct, monotypic, genus of protodipteran insect containing a single species, Choristotanyderus nanus which lived during the Permian period. The genus and species were first described by Edgar Frederick Riek in 1953 from a specimen found in New South Wales, Australia. It is considered a transitional form between Mecoptera and Diptera. The genus is placed in the protodipteran family Permotanyderidae with the related genus Permotanyderus.