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 rnas extinctions, that affect other ecosystems(1,2,4). However, little is known about ancient vent communities because fossils have been reported from very few(5-11) of a thousand or so documented vent deposits(12). 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 deposit(12). The assemblage represents the oldest, and most diverse, fossil hydrothermal-vent community known, and shares vestimentiferan and polychaete tube-worms with both modern vent communities(1,2) and other ancient vent assemblages(7-12), but is unique in baring brachiopods and monoplacophorans. Modern rant communities are not refuges for these Silurian shelly vent taxa, a finding that may have implications for the refuge hypothesis.