Pterocarya sp.(?) Flower
Green River Formation
Middle Eocene
Lincoln County, Wyoming

This well preserved specimen probably is the seed/flower of Pterocarya. The winged fruit has a few longitudinal groves and short peduncle. The wings are opposite like a butterfly and have thin veinlets radiating from the nutlet. These are rarely seen.
Pterocarya leaves and fruits are often found in the early Eocene Wind River flora near Dubois, Wyoming. The pollen of Pterocarya is also relatively abundant in samples from the lower Parachute Creek Member and thus seems to be a somewhat common element of the lower ground forests of the Green River Eocene deposits.