The oldest Hymenopteran fossils are in the family Xyelidae. There are 65 species of extant Xyelidae, sawfly-like wasps, that feed on the pollen and nectar of conifers. The Xyelidae are most noted for their unusual leg-like antennae. Like many Hymenoptera, they are recognizable from their wing venation. The Potrerillos Formation, Cuyo Basin of Argentina has produced a new fossil Xyelidae, Potrerilloxyela menendezi, that is known only from its wing. Insect wings are acellular and have properties that deter degradation by bacteria. Wings are the most common insect part that fossilizes.
The new fossil, described by Lara and colleagues*, is now the oldest Hymenopteran from Argentina. This fossil establishes that the Xyelidae appeared simultaneously in both the New and Old World. They were widespread during the days of supercontinents Laurasia and Gondwana.
*M. B. Lara, A. P. Rasnitsyn, and A. M. Zavattieri. 2014. Potrerilloxyela menendezi gen. et sp. nov. from the Late Triassic of Argentina: The Oldest Representative of Xyelidae (Hymenoptera: Symphyta) for Americas. Paleontological Journal. 48(2):182–190.