Unusual Carboniferous Stromatolite Nodule from Kansas

Coming from Kansas, this Carboniferous-age stromatolite can be considered young. By the time it was formed, the cyanobacterial organisms and their stromatolitic reef systems were becoming quite restricted on earth, having retreated to environments less favorable to other marine life (including other microorganisms, algae and animals) with which they competed or from which they suffered predation.

It acquired the name Somphospongia sp. because it was long believed to be a sponge, and the resemblance is rather striking but was later determined to be stromatolite.