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(a). Locality map, showing outcrops of Dakota Sandstone in western USA, extensively modified in Photoshop CS5 from part of a map by Carpenter (Supplementary Information S1) (b). General view of the Roubideau Creek site (photograph by senior author, M. Lockley, with coauthors KC (foreground) and JM (background) with permission. Note conspicuous scrape marks and mid-line ridge in traces 4–6, c. general view of the Club Gulch site.
