A new megaspilid wasp from Eocene Baltic amber (Hymenoptera: Ceraphronoidea), with notes on two non-ceraphronoid families: Radiophronidae and Stigmaphronidae.

Ceraphronoids are some of the most commonly collected hymenopterans, yet they remain rare in the fossil record. Mikó and Trietsch, sp. nov. from Baltic amber represents an intermediate form between the type genus, , and one of the most species-rich megaspilid genera, . We describe the new species using 3D data collected with synchrotron-based micro-CT equipment. This non-invasive technique allows for quick data collection in unusually high resolution, revealing morphological traits that are otherwise obscured by the amber. In describing this new species, we revise the diagnostic characters for Ceraphronoidea and discuss possible reasons why minute wasps with a pterostigma are often misidentified as ceraphronoids. Based on the lack of ceraphronoid characteristics, we remove Brues, 1937, Stigmaphronidae, and Radiophronidae from Ceraphronoidea and consider them as . We also provide some guidance for their future classification.