Thamnasteria

Thamnasteria is a genus of extinct cnidarians belonging to the order Faviida. These corals lived during the Jurassic period, from the Toarcian to the Oxfordian stages. Thamnasteria corals were colonial, forming large, massive structures. Their corallites, the individual cups that housed the polyps, were typically small and closely packed, often exhibiting a cerioid to plocoid arrangement where corallites share walls or are separated by stereome.

The septa, which are the internal radiating plates within the corallites, were usually numerous and finely serrated. The columella, a central pillar within the corallite, was often trabecular, meaning it was composed of a spongy or porous structure. The external surface of the colony in Thamnasteria was generally rough and irregular.

Fossils of Thamnasteria are found in marine sedimentary rocks worldwide, particularly in Europe and Asia. They are significant components of Jurassic reef ecosystems, indicating that these corals played a crucial role in building the seafloor structures of that era. The genus is characterized by its distinctive corallite morphology, which distinguishes it from other related coral genera. Studying Thamnasteria helps paleontologists understand the evolution of corals and the paleoecology of Jurassic seas.