A gigant myriapod trail from the Namurian of Arran, Scotland

A large trace fossil in the Limestone Coal Group of Arran is preserved in a deltaic, channel-fill sandstone from a cyclic sequence including coals. The trail, Diplichnites cuithensis ichnosp. nov., consists of two parallel series of closely spaced imprints, and is attributed to the giant Carboniferous myriapod Arthropleura, making this the earliest evidence for the genus. Analysis of the trail suggests the individual responsible was c. 1 m long, and had twenty-three pairs of appendages. Knowledge of modern myriapod gaits has been used to extrapolate a theoretical trail for Arthropleura, which compares well with the fossil trail. The trail suggests that a gait pattern of forestroke: backstroke of 5.5:4.5 was used in walking across the sand substrate. This contrasts with the previous estimated gait of 3.7 that Arthropleura might have used in pushing through coal-forest litter. Such a range of gaits is well within that recorded for individual Recent species of millipede. Diplichnites is emended to exclude most trilobite locomotion trails.