Lower Cambrian Yelma digitata Stromatolite from Oklahoma

This is younger Lower Cambrian stromatolite from the Arbuckle Mountains in Oklahoma. By the time this stromatolite formed, the cyanobacterial organisms and their stromatolitic reef system had already undergone steep decline, and were becoming restricted to environments less favorable to other marine life with which they competed or from which they suffered predation.

It derives its informal name, Yelma digitada, from its form-similarly to its namesake from Australia.