An important intermediate step in the evolution of pincer wasps: an extraordinary new type of chela from mid-Cretaceous Burmese amber (Hymenoptera, Dryinidae)

Raptodryinus patrickmuelleri gen. et sp. nov., that belongs to Raptodryininae subfam. nov. (Hymenoptera: Dryinidae), is described from Burmese amber. Raptodryininae subfam. nov. represents one of the first fossil groups of chelate dryinids, documenting the fact that the evolution of chela still took place at the earliest Late Cretaceous. It is characterized by a very peculiar chela, composed of a proximal lobe of the fifth protarsomere opposable on a complex composed of the fifth protarsomere + arolium + both claws. This type of chela differs completely from the common chelae of extant and known fossil pincer wasps (composed of one enlarged claw opposable on a more or less strongly projecting fifth protarsomere). The chela of R. patrickmuelleri represents probably an early evolutionary stage of pincer wasps close to the basal Dryinidae, whose females were achelate. This discovery enabled us to outline the evolution of the chela of Dryinidae. In the evolution of pincer wasps, the oldest known fossil species, Aphelopus palaeophoenicius Olmi 2000, from Barremian Lebanese amber is of special importance as a basal exemplar. We had re-examined this species and attributed it to a new genus, Archaeodryinus gen. nov., and a new subfamily, Archaeodryininae subfam. nov., documenting the first known basal achelate pincer wasp. The emended data on the subfamily Aphelopinae suggest that this taxon is known only since the Miocene and that its females had secondarily lost their chelae. The discussion on biological features of Aphelopus that enabled parasitism on Typhlocybinae (Hemiptera: Cicadellidae) is also given. (C) 2020 Elsevier Ltd. All rights reserved.