Like father, like son? Not amongst the eurypterids (Chelicerata) from Beartooth Butte, Wyoming

Abstract

The eurypteridStrobilopterus princetoniifrom the Lower Devonian Beartooth Butte Formation of Wyoming is redescribed, and previously unknown morphological features, including shape and position of eyes and ocelli are identified, and the prosomal appendages are described in more detail. The monotypicErieopterus latus, based on a much smaller specimen from the same locality, shares a large number of characters withS. princetonii, and must be interpreted as belonging to the genusStrobilopterus.It is here interpreted as a juvenileS. princetonii, but exhibits extreme ontogenetic variation in the morphology of the swimming leg. The other monotypic eurypterid from the locality,Dorfopterus angusticollis, remains mysterious. It might be aS. princetoniitelson, but evidence is inconclusive. The name of the Devonian eurypterid genusSyntomopterusis preoccupied for a beetle (Coleoptera: Insecta) and the replacement nameSyntomopterellais proposed. The phylogenetic position ofS. princetoniiis problematic since it lacks unequivocal synapomorphies with other eurypterids, but the genus is showing more similarities toSyntomopterella, ErieopterusandBuffalopterusthan it does toDolichopterus, contrary to earlier suggestions.