Genital Appendages of the Giant Pterygotid Eurypterid Acutiramus from the Silurian (Pridoli) Bertie Group of North America

Pterygotid eurypterids are known for their large size and elongate chelicerae. The Silurian Bertie Group of upper New York State has yielded complete and fragmentary specimens of giant individuals of the pterygotid Acutiramus macrophthalmus indicating maximum body lengths over 2 m. Here we describe and illustrate large, isolated examples of the otherwise poorly documented genital appendages (type A and B, generally interpreted as female and male respectively) of this pterygotid. The rarity of complete specimens of Acutiramus affording a ventral view of the body compromises attempts to infer body length from the dimensions of the genital appendages. These appendages provide useful evidence of the interrelationships of pterygotids when used in combination with other characters.