Living corals are remarkably broad in their thermal and bathymetric ranges. But corals that could tolerate abnormally high temperatures (higher than 40°C) are unknown both in the living communities and in the fossil record. Here we report the discovery of small thermophilic rugose corals in the Devonian vent community of southeastern Morocco. These organisms were adapted to conditions prevailing within chimney conduits of a hydrothermal system that developed on the roof of a submarine volcanic high. The coral larvae followed a calice-in-calice settlement and growth strategy to survive the contact with thermal fluids. This adaptation was not related to taxonomy and characteristic of all coral taxa present in the vents. Monospecific coral population was identified in several Emsian vents whereas the coral fauna of the single Givetian vent was more diverse and included four species. The entry of different rugose coral species into the hot vents resulted from a trophic relation to ostracods flourishing in the chimneys.
