An isolated ramus of the pterygotid eurypterid Jaekelopterus cf. howelli from the Early Devonian (Pragian) Beartooth Butte Formation (Cottonwood Canyon, north-western Wyoming) is described. Pterygotid taxonomy and synonymy is briefly discussed with the genera Pterygotus, Acutiramus and Jaekelopterus shown to be potential synonyms. The use of cheliceral denticulation patterns as a generic-level character is discouraged in light of variations within genera and its unsuitability as a major characteristic in the other eurypterid families.

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