Rugosa and Tabulata
Rugosa and Tabulata were corals creating reef-like structures. There is hypothesis that both groups lived in symbiosis with zooxantellas. They lived in Paleozoic. Appear in Ordovician, extinct at the end of Permian.
"A tabulate coral with individual corallites similar in size and shape to honeycomb. These extinct, almost invariably Palaeozoic corals are alway colonial. The corallites consist of slender tubes which are crossed by transverse paritions called tabulae. Septa are partly formed or absent." citation and photograph by John Veron; John Veron Corals of Australia and Indo-Pacific.
Rugosa probably had polyphyletic origin, what means that they appear in evolution of few groups not only one. Intriguing matter is relation between Rugosa and Scleractinia. There are assumptions that Scleractinia (or one of the scleractinian branches , because Scleractinia had also polyphyletic origin) arose from a branch of Rugosa. However period between extinction of Rugosa and appearing of Scleractinia extend to 5 million of years what could be an evidence of incorrectness of this hypothesis. Also dissimilarities between both groups of corals testify against hypothesis.
Differences among rugosa and scleractinia:
|1.||Rugosa made calcite skeleton, Scleractinia aragonite skeleton.|
|2.||Rugosa had bilateral symmetry of their cup-shaped calices, Scleractinia have radial symmetry|
"Rugosa corals are an extinct Palaeozoic group which may be solitary (above) or colonial (below). In either case, coralittes have a wide range of shapes and sizes. They contain tabulae (like tabulate corals) and septa (like Scleractinia corals) the latter usually being much more prominent." citation and photograph by John Veron; John Veron Corals of Australia and Indo-Pacific.