It is not easy to see the underprints (footprint impressions not on the top layer, but distortions below the surface that indicate pressure from a layer or more above) in this specimen, but look closely by clicking on the Full View icon and you will find them.
Also notice the many cracks in the rock. These cracks formed as the mud dried, shrinking a little in the process. Sediments below the dried mud then filled in the cracks.
Edward Hitchcock attributed the unusual long, narrow cracks to the result of a heavy animal walking on brittle, sun-hardened mud. He called them "sun cracks". Actually, the cracks would have formed before the animal came along. The dried mud cracks had been further covered with new soft sediments, into which the animal stepped, leaving the footprints.