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Trackways attributed to a xiphosurid arthropod) maker are described for the first time from the Middle Jurassic Saltwick Formation, Ravenscar Group, of the Cleveland Basin, Yorkshire. The trackways are assigned to Kouphichnium afl. variabilis Linck, 1949) and clearly demonstrate the heteropody and varied behaviour of the maker. Their occasional asymmetry indicates a slight rotation of the body relative to the direction of locomotion. The Saltwick Formation has generally been regarded as a coastal plain deposit, and the presence of xiphosurid tracks reinforces the suggestions of periodic marine influences. [ABSTRACT FROM AUTHOR]