Huge Domal Cryptozoan Stromatolites from Wisconsin

Coming from the Lower Ordovician Oneota Formation, it is some 495 million years old, from a time that Prokaryotic life forms no longer had exclusive use of earth's shorelines. Concomitantly, the earths coastal habitats had markedly reduced stromatolite reefs, compared to Proterozoic, Precambrian time.

By this time in geological history, microbial communities consisted of complex consortia of both prokaryotic and eukaryotic forms with diverse metabolic needs, and competition for resources and differing motility among them made for an intriguing microcosm of interacting life, some autotrophic, some chemotrophic and some heterotrophic.

This particular specimen has been cut horizontally through a vertical dome, thus revealing rings of laminae resembling that of the growth rings of a a tree. Note how the fine hand polishing reveals the stromatolitic growth history in a beautiful form. Interestingly, the edge at the top of the first photo corresponds to the shear by a glacier during the last ice age.