Silurian hydrothermal-vent community from the southern Urals, Russia

MODERN hydrothermal-vent communities are remarkable for being dependent on bacterial chemosynthetic primary production and for having a high percentage of endemic taxa (95% at the species level)1–3. Based on phylogenetic analyses, it has been suggested that some of these taxa are Mesozoic or even Palaeozoic relicts, and that the vent environment has thus acted as a refuge against evolutionary pressures, such as mass extinctions, that affect other ecosystems1,2,4. However, little is known about ancient vent communities because fossils have been reported from very few5–11 of a thousand or so documented vent deposits12. Here we describe a macrofossil assemblage of monoplacophoran molluscs, inarticulate brachiopods, vestimentiferan tube-worms and other tubes, probably of polychaete origin, from the Silurian Yaman Kasy deposit12. The assemblage represents the oldest, and most diverse, fossil hydrothermal-vent community known, and shares vestimentiferan and polychaete tube-worms with both modern vent communities1,2 and other ancient vent assemblages7–12, but is unique in having brachiopods and monoplaco-phorans. Modern vent communities are not refuges for these Silurian shelly vent taxa, a finding that may have implications for the refuge hypothesis.