sentences:  The discovery of "Ciurcopterus", the most primitive known pterygotid, and studies revealing that "Ciurcopterus" combines features of "Slimonia" (the appendages are particularly similar) and of more derived pterygotids, revealed that the Slimonidae is more closely related to the Pterygotidae than the Hughmilleriidae is.The cladogram below is simplified from a study by O. Erik Tetlie (2007), and showcases the position of "Slimonia" relative to the rest of the Eurypterina suborder of eurypterids, with the Stylonurina suborder as an outgroup.The specimen MB.A 863, a "S. acuminata" discovered in the Patrick Burn Formation (dated to the Telychian, around 430 million years ago) of Scotland, preserves a complete and atriculated series of telsonal, postabdominal and preabdominal segments.