In 1843, the English geologist and paleontologist William Buckland described the now called BGS GSM 26037 (housed at the British Geological Survey in Nottingham, England) specimen as the result of the repeated impressions of three bony processes of the pectoral fin of an ambulatory (related or adapted to walk) fish, Icthyopatolites. The specimen was collected in Mostyn, Wales, and is Westphalian (Late Carboniferous) in age. However, in 1996, Braddy and Lyall I. Anderson recognized the track as clearly that of a moderately large (around 20 cm, 7.9 in long) hexapodous arthropod similar to the eurypterid traits that were described before in other papers, and named it Palmichnium pottsae. Although the leg morphology of the Carboniferous eurypterids is poorly known or completely unknown, the trackway fits with the maximum leg span of Adelophthalmus, approximately 10 cm (3.9 in). P. pottsae produced large trackways with asymmetric rows of three paired impressions along several irregular prints. It lacked a median line, but it has been suggested that this is due to the buoyancy of the water surrounding the abdomen of the animal or the active held up of the telson on the substrate without touching it, allowing better locomotion. The total length of the trackway was 37 cm (14.6 in). The outer tracks of the right and left series of the trackway were curvilinear or linear grooves, as well as the intermediate tracks, which were smaller than the outer ones. The internal tracks of both series were the smallest and with a bifid (cleft-like) form. There were also several irregular tracks that did not belong to any of the series. Although the assignment of P. pottsae to Palmichnium should mean the synonymy of Icthyopatolites with the first ichnogenus, Braddy and Anderson avoided formally synonymizing them because Buckland informally described Icthyopatolites and without an established diagnosis. Early Devonian trackways have also been found in Alken an der Mosel, Germany.
