The Devonian was a period in Earth's history.

Kirisha IV is similar to Earth in the Devonian. (TNG novel: The Buried Age)

In 2370, Benjamin Sisko, Jake Sisko, Quark and Nog visited a planet in the Gamma Quadrant that Starfleet had analyzed to be like Earth during the early Devonian period. (DS9 episode: "The Jem'Hadar")