Eldredgeops [Phacops] rana is a species of trilobite from the Devonian period (~390 million years ago) that is most commonly found in the northeast US, Ontario and Morocco. Eldredgeops like this one is often found in the #1 fossil park in the U.S.--the Penn Dixie Quarry of Hamburg, New York. 

Rana is Latin for “frog” and the Greek root, fakos, means “lens” as the bulbous eyes of these trilobites have a strong resemblance to those of frogs. Their highly sophisticated eyes had calcite lenses, depth perception, color perception and were able to swivel 360° allowing them to always be on the lookout for potential predators. Not only did these advanced eyes survey for danger, but they also are an indicator of the predatory nature of Eldredgeops rana as they probably spent most of their lives on the ocean floor eating other smaller aquatic animals and larvae.

These trilobites could grow between .5 inches to over 4 inches long, making them some of the largest arthropods of their time.

The glabella (or nose-like part) acted as part of their digestive system and was large with many bumps. This feature as well as their schizochroal eyes make the Eldredgeops rana one of the most recognizable trilobites. Its head (the cephalon), thorax, and tail (pygidium) are fairly rounded and plain.

Like present-day horseshoe crabs, as Eldredgeops grew it would molt its exoskeleton. When it felt threatened, it would roll up into a tight ball using its tough exoskeleton as protection, sometimes accidentally burying itself alive under sediment and becoming fossilized. 

Type: Trilobite
Species: Eldredgeops [Phacops] rana
Age: Middle Devonian (387 - 382 million years old) 
Formation: Moscow Formation
Locality: Penn Dixie Quarry, Hamburg, New York

Size of plate: 4 x 3.38 x 1 inches
Size of specimen: .88 x .81 inches
Weight: 8.20 oz.