Sphecomyrminae
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 eight genera, divided into two tribes Sphecomyrmini and Zigrasimeciini. The tribe Sphecomyrmini contains the six genera "Armania", "Cretomyrma", "Gerontoformica", "Orapia", "Pseudarmania" and "Sphecomyrma"; while Zigrasimeciini contains "Boltonimecia" and "Zigrasimecia". A number of taxa have been removed from the subfamily and placed either in other subfamilies or are now treated as "incertae sedis" in Formicidae. Sphecomyrminae is the most basal of the Formicidae subfamilies, but has not been included in several 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. Tribes and genera. A 2017 study recognized three tribes, Haidomyrmecini, Sphecomyrmini, and Zigrasimeciini  and included the genera formerly placed in Armaniidae within the tribe Sphecomyrmini. Further review of the haidomyrmecins resulted in them being elevated to the separate subfamily Haidomyrmecinae and removed from Sphecomyrminae. The genus "Sphecomyrmodes" was formerly placed into Sphecomyrmini; however, in 2016, it was made a synonym of the stem group genus "Gerontoformica", which was considered "incertae sedis" in Formicidae at the time. The former tribe Zigrasimeciini is now considered to comprise the separate subfamily Zigrasimeciinae.