limnades, P. traquairi, Pyritocephalus youngii and Millerolepis eleionomae. Vernonopterus and these fish would have lived in a brackish fresh water environment. Hibbertopterids such as Vernonopterus were sweep-feeders, having modified spines on their forward-facing prosomal appendages that allowed them to rake through the substrate of their living environments. Though sweep-feeding was used as a strategy by many genera within the Stylonurina, it was most developed within the hibbertopterids, which possessed blades on the second, third and fourth pair of appendages. Some species of the closely related Hibbertopterus had specialized comb-like rachis (shafts) that were able to entrap small prey and other organic food particles. Though they would have been slow owing to their massive size and robust form, studies on Hibbertopterus footprints discovered in Scotland have demonstrated that hibbertopterids would have been able to walk on land for at least short periods of time. The tracks discovered indicate that they would have utilized a lumbering, jerking and dragging movement and that the keeled belly and the telson left a central groove behind. Some studies suggest that eurypterids possessed a dual respiratory system (capable of breathing in both air and underwater), which would have allowed for this kind of occasional terrestrial movement. See also List of eurypterid genera Timeline of eurypterid research References Carboniferous eurypterids Stylonurina Eurypterids of Europe Carboniferous arthropods of Europe