New species of Tridactyloidea (Orthoptera, Caelifera) from mid-Cretaceous Burmese amber show an intermediate evolutionary state between extant lineages

Two new genera and species of Tridactyloidea Brullé, 1835 from mid-Cretaceous Burmese amber are described. Abaddonella nwarrngaal gen. et sp. nov. is based on a well-preserved male specimen. It is assigned to Ripipterygidae Ander, 1939 due to its one-segemented cercus and the mesotibia not being significantly wider than mesofemur.

The new genus is similar to Burmaripipteryx Zhao, Xu, Jarzembowski, Fang & Xiao, 2023 in regard to its abdominal and external genitalia morphology, but it differs from the latter genus (as well as other Ripipterygidae) by two small bumps on the vertex in front of the eyes. The second new taxon described is named Naginipteryx pinna gen. et sp. nov. Despite exhibiting a distinct ripipterygid-like morphology of the external genitalia, it shows a very inflated mesotibia with a marked triangular shape.

This feature is usually considered to be diagnostic of Tridactylidae Brullé, 1835. The taxonomic position of N. pinna, therefore, is difficult. For now, the species is placed outside both families (Ripipterygidae and Tridactylidae) and is suggested to be an ancestor of both lineages, prior to the evolutionary separation being completed.

An identification key to the genera of Ripipterygidae from Burmese amber is provided.