Hit and miss (A comment on persons and acorn, “a sea scorpion’s strike: New evidence of extreme lateral flexibility in the opisthosoma of eurypterids”)

W. Scott Persons IV and John Acorn, in their paper “A Sea Scorpion’s Strike: New Evidence of Extreme Lateral Flexibility in the Opisthosoma of Eurypterids,” appearing in the July 2017 issue of The American Naturalist, suggested a radical new mode of hunting for eurypterids involving extreme lateral flexibility that permitted the telson to slash and stab at prey, implying that eurypterids were better armed than previously supposed. Here, we show that the interpretation is based on a molt that is strongly curved because of taphonomic processes and does not reflect trunk flexibility in life. Hydrodynamic considerations reveal that the telson was not suitable for rapid lateral movement, confirming that the eurypterid telson functioned in aiding balance and generating lift during locomotion, not as a weapon.