Two Palaeozoic hydrothermal vent communities from the southern Ural Mountains, Russia

The Sibay and Yaman Kasy massive sulphide deposits contain macrofossil asse mblages that represent some of the oldest known hydrothermal vent communiti es. The deposits are hosted respectively by Middle Devonian and Silurian ar e-related volcanic rocks in the Ural Mountains of Russia, and formed under the same environmental constraints as modern vent sulphides. The Sibay pala eocommunity comprises, in order of decreasing abundance, tubes of an indete rminate ?annelid and the vestimentiferan Tevidestus serrriformis Shpanskaya , Maslennikov and Little and articulated specimens of the modiomorphid biva lve Sibaya ivanovi gen. et sp. nov. The Yaman Kasy palaeocommunity comprise s, in order of decreasing abundance, tubes of the ?polychaete Eoalvinellode s annulatus gen. et sp. nov. and the vestimentiferan Yamankasia rifeia Shpa nskaya, Maslennikov and Little, and specimens of the ?kirengellid tergomyan Themoconus shadlunae gen. et sp. nov., the lingulate brachiopod Pyrodiscus lorrainae gen. et sp. nov., an indeterminate vetigastropod, and the ambony chiid bivalve Mytilarca sp. Some of these taxa have affinities to endemic t axa at modern hydrothermal vent sites and some belong to taxa that are typi cal of Palaeozoic non-vent marine palaeocommunities. Therefore, there has b een movement of taxonomic groups in and out of the vent ecosystem through t he Phanerozoic.