Coming from the Cambrian-age Krukowski quarry in central Wisconsin, this Protichnites ichnofossils may well represent some of the earliest animal footprints on land. When these footprints were made, what is now Wisconsin was some 10 degrees below the equator, and paleontologists believe the site was once a beach of a shallow marine environment.

No shelly animals are found in the Krukowski quarry, only trackways (ichnofossils) and body impressions (such as in the case of the Jellyfish (Cnidarians) and Arthropod carapaces of the likely animal to have made Protichnites and Diplichnites trackways. Besides a few mysterious trackways that cannot be named, one finds Diplichnites, Protichnites and Climactichnites. Together, this quarry tells a story just now being researched by paleontologists - hopefully, the result will be some shedding of more light on when and how life first ventured from marine to land environment.

Protichnites is a generic genus of trace fossil that are the imprints made by the feet of walking arthropods. These fossils are normally found in what were shallow-water areas and tidal zones of Paleozoic shorelines, and are also known from the Cenozoic fossil record. There is an enormous diversity of arthropods that could have been responsible for Protichnites; In terms of the upper cambrian Krukowski quarry, putative trackmakers include Euthycarcinoids, aglaspidids, and eurypterids. The Protichnites ichnogenus comprises two approximately parallel rows footprints together with a longitudinal depression, normally between footprint rows. The depression can be constant or piecewise dashes, and is considered to be the consequence of a dragging body appendage such as a telson (tail).

The maker of the Protichnites fossil trackways might also have been an animal resembling the extant but ancient horseshoe crab, except of an early design that lacked a hard shell to be preserved. Others have posited that Protichnites was a soft-bodied progenitor of the large, now extinct group of early predators, the Eurypterids (Chelicerate "biting claws" Arthropods). Still, the most popular choice is a member of the aglaspids, which is supported by putative body fossils of them found in the quarry. It is entirely rational that the animal maker of Protichnites also made the Diplichnites tracks. Diplichnites lacks the telson drag marks, which might be explained by behavior, locomotion, feeding behavior or even tide level - and so continues the mystery of these two ichnogenera in the quarry.

This particularly large specimen is one of the finiest and most intriguing found at the site. There is a mryiad of footprints, footdrags or slashes, and tail drag marks left in the Cambrian-age sand. Tracks are generally overlayed, with some curved, some straight, and some sharply cuved. The hyporelief tracks are exceptionally thicker and higher than most, suggesting a helter-skelter flurry of many larger arthropods, that carved deep and wide grooves in the sand of a Cambrian shoreline.

Also see: Cambrian Shadows Theme Park