Eldredgeops rana

Eldredgeops rana (synonym Phacops rana) is a kind of ancient sea creature called a trilobite that lived during the middle Devonian period, a time long ago when the world looked very different. Fossils of Eldredgeops rana are most often found in parts of the northeastern United States and southwestern Ontario.

This trilobite is well-known and popular among people who collect fossils. Because of this, Eldredgeops rana was chosen to be the special state fossil of Pennsylvania. This honor was given by the state's leaders on December 5, 1988, showing how important this fossil is to the area.

Description

Eldredgeops rana is known for its large eyes, which look a bit like a frog's eyes—this is why it is named after a frog. It could grow up to 6 inches long and had a special way to stay safe. Like a pill bug, Eldredgeops rana could roll up into a ball using its hard exoskeleton to protect itself from predators. This rolling trick, called "volvation," almost always helped it hide from danger. However, sometimes it would roll into a spot with too much sediment and get stuck. Even today, we can still see fossils of Eldredgeops rana in this curled-up position, showing how they tried to protect themselves long ago.

Fossilisation

Eldredgeops rana fossils are found in the northeastern U.S. and southwestern Ontario. During the Devonian period, North America was connected to the African Plate.

Phacopid eyes

The most noticeable feature of Eldredgeops rana and its relatives is their eyes. These eyes were different from most trilobites because they had fewer lenses spaced far apart in deep sclera. The lenses were very rounded, not flat, and the eyes sat on structures that could move, giving the animal almost a full-circle view. This special type of eye is called the schizochroal eye.