Wikipedia
Sphecomyrminae is an extinct subfamily of ants in family Formicidae known from a series of Cretaceous fossils found in North America, Europe, and Asia. Sphecomyrminae contains nine genera, divided into two tribes, Haidomyrmecini and Sphecomyrmini. The tribe Haidomyrmecini contains the four genera Ceratomyrmex, Haidomyrmex, Haidomyrmodes and Haidoterminus, while Sphecomyrmini contains Baikuris, Cretomyrma, Dlusskyidris, Sphecomyrma, and Zigrasimecia. The genus Sphecomyrmodes was formerly placed into Sphecomyrmini; however, in 2016, it was made a synonym of the stem group genus Gerontoformica, which is considered incertae sedis in Formicidae.
Sphecomyrminae is the most basal of the Formicidae subfamilies, but has not been included in several recent phylogenetic studies of the family. Symplesiomorphies of the subfamily include the structure of the antenna, which has a short basal segment and a flexible group of segments below the antenna tip. The petiole is low and rounded, with an unrestricted gaster and the presence of a metapleural gland. The subfamily is characterized by three major synapomorphies, the short pedicel, a second flagellar segment that is double the length of the other antenna segments, and the loss of the apical end of the CuA veins in the wings of adult males.