Abstract
A flat wasp specimen attributed to the genus Eupsenella Westwood, 1874 is described and figured from the early Eocene compressions of the Green River Formation. This fossil is the first known outside of the Old World for this genus and documents its wide distribution during the Paleogene, while it is currently confined to Australia and New Zealand. As for several other hymenopteran genera, we assume that this regression is linked to abiotic factors, i.e., the Cenozoic climate cooling, rather than to biotic factors.