Dragonflies, from the order Odonata, have been around for over 250 million years.  I've seen fossil dragonflies from the Eocene some 50 million years ago that would have been exquisite monsters to behold. Huge beasts taking to the skies and enjoying the warmth that the Earth was experiencing at the time.
The most conspicuous difference in their evolution over time is the steady shrinking of their wingspan from well over two and a half feet down to a few inches.

Metasequoia, a deciduous conifer, and one of the common fossils found in many of the Eocene sites of the Pacific northwest, flourished in Oregon's forests for millions of years. In honor of this long history, Oregon has named it their official state fossil. 

The Columbian Mammoth, the official state fossil of Washington, crossed the Bering Land Bridge into North America some one million years ago and made a home roaming the vast grasslands that stretched from Alaska to Mexico, mirroring the great Rocky Mountains, and munching down about 300 pounds of vegetation each day. During the Pleistocene this extinct elephant extended his habitat down into Central America to modern day Nicaragua and Honduras before dying out around 12,500 years ago.

Much of the island of Crete is Miocene and filled with fossil mollusks, bivalves, gastropods who lived 5 to 23 million years ago in warm, tropical seas. They are easily collected from their pink limestone matrix and are often eroded out, mixing with their modern relatives.

Elasmosaurs loved their gastroliths – round, polished stomach stones – have been found amid their bones. These stones would have been swallowed to help grind down their catch and lower their natural buoyancy. Surprisingly elasmosaurs displayed a remarkable discernment in their selection of pebbles. The Puntledge elasmosaur from Courtenay, British Columbia, for example, had a yen extrusive volcanic rock. When the fossilized skeleton was excavated, every last one of the stones in its abdominal cavity were basalt.

Two hundred million years ago, Washington was two large islands, bits of continent on the move westward, eventually bumping up against the North American continent and calling it home. Even with their new fixed address, the shifting continues; the more extreme movement has subsided laterally and continues vertically. The upthrusting of plates continues to move our mountain ranges skyward – the path of least resistance. This dynamic movement has created the landscape we see today and helped form the fossil record that tells much of Washington’s relatively recent history – the past 50 million years.