Hexagonaria percarinata Stumm, 1969 - fossil rugose coral from the Devonian of Michigan, USA. (polished surface; field of view ~3.6 cm across)
The “official state stone” of Michigan is the Petoskey Stone, the local name for rounded pebbles or cobbles of the fossil colonial rugose coral Hexagonaria percarinata. Petoskey Stones have been weathered & eroded from fossiliferous limestones of the Traverse Group (Middle Devonian). They are particularly common in the vicinity of Little Traverse Bay & the town of Petoskey (northwestern Lower Peninsula of Michigan). Beach & lake gravel in this area consist of many lithologies, including fossiliferous limestone clasts and worn fossil corals (favositids & colonial rugosans).
The city of Petoskey, Michigan gets its name from an old Ottawa Indian Chief, Ignatius Petosega. “Pet-o-sega” means “rays of the rising sun”. Petoskey Stones are so-named in reference to the dark-colored “eye” & radiating lines of individual Hexagonaria corallites.
Classification: Animalia, Cnidaria, Anthozoa, Rugosa, Phillipsastraeidae
Stratigraphy: Traverse Group, Middle Devonian
Locality: unrecorded/undisclosed site in Michigan, USA
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See info. at:
en.wikipedia.org/wiki/Rugosa
