n large amphibious animal 

Perception +10; darkvision, wavesense (imprecise) 30 feet

Skills Athletics +13, Stealth +13

Str +4 Dex +2 Con +5 Int -5 Wis +1 Cha -3

AC  22; Fort +16, Ref +11, Will +10

HP 70

Attack of Opportunity [R] Stinger only (page 304).

Chitinous Spines A creature grabbed by the spiny eurypterid takes 2d6 piercing damage at the start of that creature's turn.

Speed 40 feet, swim 40 feet

Melee [>] pincer +15, Damage 2d8+4 slashing plus Grab

Melee [>] stinger +15, Damage 2d6+4 piercing plus spiny eurypterid venom

Spiny Eurypterid Venom (poison) Saving Throw DC 22 Fortitude; Maximum Duration 6 rounds; Stage 1 1d8 poison damage and enfeebled 1 (1 round); Stage 2 1d8 poison damage and enfeebled 2 (1 round); Stage 3 2d8 poison damage and enfeebled 3 (1 round)

Bestiary 3, page 97.