Middle Miocene

Esmeralda Formation

Nye county, Nevada, USA

Fine 0.35 inch acorn cup

Seed,

Quercus is the genus for oak trees.  The earliest confidently-recognized fossils are pollen from the Late Paleocene of Austria, and by the Middle Eocene, Quercus was widely-distributed from North America to Europe and Asia.  Oaks originated in tropical forests but they continued to thrive while other trees retreated to lower latitudes as climates became drier and cooler across the Oligocene and Miocene.  Many modern species may have appeared around the time this seed was alive.