Staghorn coral (the delectably named Stereolasma rectum Devonian, Finger Lakes, Western New York)

400 million year old Rugosa corals, know as "Staghorns" locally, so freshly unearthed they look alive.  I thought for a moment they may have been slugs or fungus, but they are very much stone.  They etched out beautifully from the top of 3 foot thick slab of Staghorns unearthed by recent rain.