Fossils

Two blocky pieces of petrified wood. Left is mustard yellow with splashes of rust red and brown-green stripes. Labeled YELL92933-1. Right is rust red with spots of white and some yellow. Labeled YELL 92933-2. Ruler in front of pieces shows they are combined a little over 150 milimeters YELL_92933 Petrified wood; Photo by Megan Norr; March 2016

Imprint of a rounded tree leaf in a rock. The rock is broken, so only part of the leaf is intact. The ruler next to the rock shows the rock is about 100 millimeters long YELL_2323 Fossil angiosperm leaf; Photo by Megan Norr; March 2016

About

The fossil record of Yellowstone is one of the most diverse in the NPS. Fossil of plants, invertebrates, vertebrates, and trace fossils have been identified in Yellowstone National Park from more than 40 stratigraphic units (rock layers of known age and origin) spanning more than 540 million years from the Cambrian to the Cenozoic eras.

Although the park’s paleontologic resources are extensive and scientifically valuable, it is estimated that only 3% of the park’s potentially fossil-bearing units have been assessed. Erosion is the key to discovery of nearly all paleontological specimens; however, once exposed, fossils are subjected to physical and chemical forces that can quickly become destructive to them. (National Park Service)