New insights into the phylogeny of Stephanidae (Hymenoptera: Apocrita), with a revision of the fossil species

The family Stephanidae (Hymenoptera) constitutes a unique group within the Apocrita, playing a pivotal role in the evolution of parasitoid wasps. Although the phylogeny of Stephanidae has been previously inferred, it remains at a low resolution when considering both extinct and extant genera, as well as the enigmatic extinct genus †Electrostephanus. Here, we undertake a revision of Stephanidae extinct, presenting descriptions of new specimens from late Cretaceous Burmese amber and early Eocene Baltic amber. Combining all extant and extinct genera, the phylogeny of Stephanidae was analyzed, incorporating 57 species within 21 genera based on 64 morphological characters. We apply both under maximum parsimony with equal weighting and implied weighting methods, with four species representing early Apocrita as outgroups. Divergence times are estimated by utilizing extinct taxa as calibration points. A new basal subfamily of stephanid wasp, †Lagenostephaninae subf. nov. was established, encompassing †Lagenostephanus and the newly described genera †Tumidistephanus gen. nov and †Neurastephanus gen. nov. The genus †Electrostephanus is redefined, with two species assigned under distinct genera, †Neurastephanus gen. nov. and †Aphanostephanus gen. nov.. We discuss some of the putative morphological synapomorphies of evolutionary significance within the phylogenetic framework. Our results complement several characteristics of great taxonomic importance for Stephanidae and provide new insights into the early evolution of the family.