A microbial mat of a large sulfur bacterium preserved in a Miocene methane-seep limestone

A Miocene methane-seep limestone from the Romagna Apennine (Pietralunga, Italy) was found to contain an extraordinarily well-preserved microbial mat consisting of filamentous fossils. Individual filaments of the lithified Pietralunga mat are 50 to 80 μ m in diameter and resemble the sulfide-oxidizing bacterium Beggiatoa. Mats of sulfur bacteria are common around modern methane-seeps, but have not yet been reported from ancient seep limestones.