A new sawfly fossil from the lower Cretaceous of China elucidates antennal evolution in the lower Hymenoptera (Pamphilioidea: Praesiricidae: Archoxyelydinae subfam.n.)

摘要

Archoxyelyda mirabilis gen.n. and sp.n., is described from the Yixian Formation of Liaoning Province, China. It is placed in the family Praesiricidae based on the loss of forewing Sc. The fossil is placed in Archoxyelydinae subfam.n. based on a modified antennal flagellum (consisting of two distinct multisegmented parts: a thick and tightly connected basal part, and a thin and more loosely articulated distal one). The incompletely preserved genus Xyelydontes Rasnitsyn, 1983 is tentatively transferredto Archoxyelydinae. The new material demonstrates a unique feature in the antennal anatomy: the composite third antennomere can be seen to consist of tightly connected primary antennomeres. Antennal evolution in the lower Hymenoptera is reviewed and three hypothetical pathways in their transformation are discussed.