Still the uniform conventional system of corals reflecting all their variety and related relationship is not developed yet. Therefore we will speak not about concrete taxons (group,, and about their natural groups.
Octocorallia or (eight-beam corals) for which eight mezenteriya, eight plumose feelers and an internal spikulny skeleton are in most cases characteristic. Undoubted representatives are known from a silur. Includes the following groups:
It is also possible to distinguish some groups from skleraktiniya (a suborder, the main of which astrotsenina (usually colonial corals, korallita small, septa consist of a small number of trabeculas), fungiina (single and colonial, korallita large, trabeculas are numerous. Septa are, as a rule, punched (porist. Sinaptikula – the skeletal elements formed by accretion of outgrowths of trabeculas of lateral surfaces adjacent, faviina (the single and colonial polipnyak consisting of large korallit are characteristic; trabeculas numerous; sinaptikula are developed as an exception.
The third subclass – Zoantharia (zoantariya). These are single or colonial corals which majority has an external carbonate skeleton (besskeletny forms are known). Are known probably since the Cambrian. It is possible to distinguish the following groups from zoantariya.
Among tabulit distinctly some groups (groups or a suborder are allocated: for example, sotopodobny favozitida, chained halizitida, siringoporida with very characteristic connecting tubes, sartsinulida which polipnyak are very similar on already mentioned modern a tubipor and nekotoy others.
Rugosa. Rugoza or four-beam corals. Single or pseudo-colonial corals with external carbonate (most likely, initially kaltsitovy) a skeleton and six primary mezenteriya which are answered respectively six primary (). Septa are in most cases put by trabeculas, there are they in four sectors from six formed by protosepta. The bottoms, often dissepiment, sometimes difficult axial columns are developed. Dvustoronne the symmetric. The middle Ordovician – Perm.