Hexagonaria Fossil Reef Sea Coral Rugosa Tetracoral Paleozoic Devonian Collection (1)

Hexagonaria was a kind of Coral (Coelenterata or cnidarians), now extinct, belonging to the Stauriida, family Disphyllidae. Fossils of this common constituent of coral reefs may be found in rock formations dating back to the Devonian period, about 350 million years ago.

Although the first appearance of corals dating back to the Cambrian period, about 542 million years ago, fossils of these organisms are extremely rare until the Ordovician period, 100 million years later, when spread the rough and tabular Tetracoral forms. The number of tabular corals began to decline during the middle of the Silurian period, and became extinct at the end of the Permian period, 250 million years ago. Corals rough, instead, became dominant by the middle of the Silurian period, and became extinct at the beginning of the Triassic period. For long periods of our geological past, so the corals were very abundant. Existed in both forms solitary that colonial and, as modern ones, these their ancestors formed of large barriers with their skeletons, compounds from one form of calcium carbonate known as calcite, while other species, as Exacorals, were composed of a different form of calcium carbonate known as aragonite, although it is less easily stored and then the fossil found are rare.