Sabalites sp.
Leaf
Early Eocene
Green River Fm.- Parachute Creek Mbr.
Douglas Pass, Colorado, USA

Extremely rare 98mm palm leaf on 130mm slab.

Sabalites is a genus of palm tree that lived in the Rocky Mountain region of North America across a long interval of time (Cretaceous to Middle Eocene) when it was covered by tropical forest.  It would have looked like Florida out there with lowland swamps alive with softshell turtles and alligators until you saw some of the mammals (dog-sized horses running by and lemur-like primates in the trees).

Sabalites disappeared from North America by the end of the Eocene as climates cooled and the Rocky Mountains rose toward the skylines we know today. This palm would survive elsewhere in the world but disappear by the end of the Miocene Epoch as climates continued to cool on the way to major glacial advances from the poles (the Ice Ages of the Pleistocene).

Nice contrast against the light-colored matrix.