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| Eldredgeops rana | |
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Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | †Trilobita |
| Order: | †Phacopida |
| Family: | †Phacopidae |
| Genus: | †Eldredgeops |
| Species: | †E. rana |
| Binomial name | |
| †Eldredgeops rana (Green, 1832) | |
| Subspecies[1] | |
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Eldredgeops rana (formerlyPhacops rana) is a species oftrilobite from the middleDevonian period. Theirfossils are found chiefly in the northeasternUnited States, and southwesternOntario.
Because of its abundance and popularity with collectors,Eldredgeops rana was designated thePennsylvaniastate fossil by the state's General Assembly on December 5, 1988.[2]
Eldredgeops rana can be recognized by its largeeyes (which remind some observers of afrog's eyes—the specific namerana is a reference to a common frog), its fairly large size (up to 6 inches long), and its habit of rolling up into a ball like apill bug ("volvation"). In order to protect themselves frompredators,Eldredgeops rana would roll into a ball with its hardexoskeleton on the outside as protection. Many other trilobites possessed the same ability, butEldredgeops rana nearly perfected it. The slightest amount ofsediment would trigger their senses, andEldredgeops rana would be hidden in a tiny shelter made of its own body.[citation needed] Although this safety feature often helped them to evade predators, occasionally it backfired and the trilobite would be buried under heavy sediment. Theirfossils can still be found in balled-up positions 400 million years later.
Eldredgeops rana is found in the northeastern U.S, southwestern Ontario, and in Morocco; North America was attached to theAfrican Plate during the Devonian.
The most striking feature of themorphology ofEldredgeops rana and its relatives is theireyes. These differed from the eyes of most trilobites in having comparatively few lenses spaced between deepsclera. The lenses themselves were very rounded instead of largely flat. The eyes were mounted on turret-like structures which could swivel, providing the animal with an almost 360-degree field of view. This type of eye is known as the schizochroal eye.
