New Early Jurassic sawflies from Luxembourg: the oldest record of Tenthredinoidea [Hymenoptera: Symphyta]

Pseudoxyelocerus bascharagensis gen. et sp. nov., the oldest representative of the Tenthredinoidea and Xyelotomidae, based of a single forewing, and an enigmatic “Symphyta” family incertae sedis, based on a hindwing, are described from the Toarcian of Luxembourg. The relationships of the genera currently included in Xyelotomidae are briefly discussed. The genera Undatoma, Liaotoma, Leridatoma, and Davidsmithia have the unique apomorphy in the wing venation of the Tenthredinoidea minus Xyelotomidae. The Xyelotomidae is probably a paraphyletic family. Only a phylogenetic analysis will help to solve these problems. There is no evidence supporting the previous assignments of the fossil genera Vitimilarva and Kuengilarva to the family Xyelotomidae.