横板珊瑚目纲

名字

由于在海底固定着生活，所以具有很发达的床板(tabulae)而得名。

特征

它们大部分是群居的，是由形成单个六角形珊瑚虫个体所组成的珊瑚，外观类似蜂巢。相邻的珊瑚从个体会由多具连接的构造。它们的特点是每个细胞内都会有发达的床板（tabulae），但几乎没有垂直内部隔板（septa）。 珊瑚虫个体长度一般0.5～4毫米，不过聚集也大1~7公分的珊瑚化石大小。

历史

横板珊瑚亚纲是由寒武纪大爆发的其中一个珊瑚分支，甚至比皱纹珊瑚还要早2400万年。在之后成功地躲过奥陶纪-志留纪灭绝事件、泥盆纪后期灭绝事件、二叠纪-三叠纪灭绝事件、不过在三叠纪的卡尼期洪积事件（Carnian Pluvial Event）灭绝了。

分类

• †喇叭孔珊瑚目 Auloporida Sokolov, 1947
• †蜂巢珊瑚目 Favositida Wedekind, 1937
• †链珊瑚目Halysitida Sokolov, 1962
• †日射珊瑚目 Heliolitida Frech, 1897
• †苔癣珊瑚目 Lichenariida Murray, 1985
• †多孔珊瑚目 Sarcinulida Sokolov, 1962
• †细管珊瑚目Syringoporida Sokolov, 1962
• †横板珊瑚亚纲地位未定 Tabulata incertae sedis
• †Somphophora属 Lindström, 1883

Tabulata, commonly known as tabulate corals, is a class of extinct corals.

They are almost always colonial, forming colonies of individual hexagonal cells known as corallites defined by a skeleton of calcite, similar in appearance to a honeycomb. Adjacent cells are joined by small pores. Their distinguishing feature is their well-developed horizontal internal partitions (tabulae) within each cell, but reduced or absent vertical internal partitions (septa). They are usually smaller than rugose corals, but vary considerably in shape, from flat to conical to spherical.

Around 300 species have been described. Among the most common tabulate corals in the fossil record are Aulopora, Favosites, Halysites, Heliolites, Pleurodictyum, Sarcinula and Syringopora. Tabulate corals with massive skeletons often contain endobiotic symbionts, such as cornulitids and Chaetosalpinx.

Like rugose corals, they lived entirely during the Paleozoic, being found from the Ordovician to the Permian. With Stromatoporoidea and rugose corals, the tabulate corals are characteristic of the shallow waters of the Silurian and Devonian. Sea levels rose in the Devonian, and tabulate corals became much less common. They finally became extinct in the Permian–Triassic extinction event.