Limnobiophyllum scutatum
Angiosperm
Early Eocene
Green River Formation- Parachute Creek Mbr.
Douglas Pass, Colorado, USA

24mm leaf on 97mm shale.

Limnobiophyllum was a free-floating, aquatic flowering plant known from the Cretaceous to Miocene of North America and Eurasia.  It has been assigned to the duckweed family, Lemnaceae, by some researchers and to the arum family, Araceae, by others.