Pterygotus macrophthalmus   scale in cms CLASS - Merostomata ORDER - Eurypterida FAMILY - Pterygotidae GENUS/SPECIES - Pterygotus macrophthalmus ROCK UNIT - Fiddler's Green Formation AGE - Upper Silurian (410 million years old) LOCALITY - Passage Gulf, Herkimer Co., New York Eurypterids or "sea scorpions" have 6 pairs of arms. The first pair (closest to the mouth) end in claws or "chelae." The claw-bearing arms of most eurypterids are very small, and are designed to cut up food fragments and transport them to the mouth. In contrast, both the claws and the claw-bearing arms of the family pterygotidae (which includes Pterygotus) are very large. This claw portion of Pterygotus macrophthalmus (CU 40979) displays the large barbs or "teeth" so characteristic of the pterygotid sea scorpion claws. One such claws in the Cornell University Collection (also housed at PRI) measures more than 20 cm (8 inches) long. Unlike most eurypterids, the chelicera (claw-bearing arms) of Pterygotus were well adapted for defense and prey capture. CU 40979