Enigmatic Cambrian Climactichnites Ichnofossil

This unique Cambrian inchnofossil comes out of a sensational sandstone formation in Central Wisconsin that was once a tidal beach, resulting in the distinctive ripples you see on the matrix surface. At present, it is generally accepted that the age of this sandstone unit is Middle Cambrian and thus represents an outlier of the Mount Simon Sandstone. This quarry has been producing some intriguing trace or ichnofossils, including huge madusae, tentacled jellyfish, Diplichnites, Protichnites, and the Climactichnites you see here, among others.

The depositional environment in this quarry varies from very shallow marine to aerial. This is very significant as the ichnofossils from this locality may be the earliest evidence of large organisms and carnivores abandoning their marine habitat to utilize the terrestrial environment. If verified to be Middle Cambrian, these ichnofossil may pre-date the Cambrian-Ordovician trackways from Canada just described in the May 2002 issue of Geology.

Climachtichnites has been described as looking like the track of a motorcycle that drove across rippled sand. The ripples in the sandstone confirm that the layer is an upper bedding plane. If Climachnichnites is a trackway, the traverse ridges can be viewed as made by muscular undulation as the animal motivated through the sand above the water. Also note the ridges on the margins on the tracks, the same as the ridges that build on either side of blade of a bulldoser. One theory of Climactichnites is that it was made by a large slug, others believe a mullusk.

While not as sharp and distinct as the better specimens, this Climactichnites is unusual compared with most owing to the curvature of the trackway. The preponderance of Climactichnites are based on straight locomotion.