Tabulata
| Tabulata | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Syringopora sp. |
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| Temporal occurrence | ||||||||||||
| Ordovician to Perm | ||||||||||||
| 485.4 to 251.9 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Tabulata | ||||||||||||
| Milne-Edwards & Haime , 1850 |
The Tabulata are an extinct order of the Hexacorallia that lived from the Ordovician to the late Permian . The name "Tabulata" ("bottom corals") comes from the horizontal plates in the skeleton of the individual polyps ( Latin tabulatus - paneled). The 300 described, exclusively colonial living genera of the Tabulata were the first reef formers among the flower animals alongside the rugosa (wrinkled corals) . It is not known whether there was a symbiosis with algae ( zooxanthellae ), as was the case with recent corals . They flourished, i.e. the maximum number of species, from the Lower Silurian to the Upper Devonian . With the stromatopores and the rugosa they formed the typical stromatopore tabular reef systems during this period.
In the Upper Devonian occurred due to heavy sea level rises ( " Kellwasser Event ") to the mass extinction of Rugosa and tabulata, 90% of the shallow-water and 50% of the deep-water forms disappeared. They didn't recover from it. During the great mass extinction at the Permian / Triassic border, they finally died out like many other living things.
anatomy
The individual organisms of a colony are called corallites and are connected to one another through pores or channels. Inside they are divided by transverse floors known as tabulae. In contrast to the rugosa, the longitudinal folds in the inside of the body (septa) are not fully developed, mostly thorns or spines that extend from the inner walls. The external shape of the colonies can be very different, bulbous, spherical but also knotty shapes are known. The individual individuals have calyx openings on the surface of the colony, they probably served as an inlet and outlet for filtering the water. These openings were often only a few millimeters in size and mostly round in shape.
Systematics
The different groups of tabulata can u. a. differ by the shape of the septa and soil. A find from South Australia, the genus Moorowipora chamberensis from the Lower Cambrian can possibly be added to the tabulates. This assignment is controversial, however, certain finds come from the lower Ordovician. The Chaetetida are an extinct group of animals with calcareous skeletons that were temporarily placed among the taboo corals, today they are mostly assigned to the calcareous sponges .
Some example genera:
Sarcinula : They only occurred in the Ordovician and were found in Europe, North America and Asia.
Heliolites : This genus existed from the Middle Ordovician to the Middle Devonian and was distributed worldwide. The colonies are usually spherical or mushroom-shaped. The tubes of the individual individuals are surrounded by skeletal material and do not touch. They are connected by tubes, pores are never there. There are always six, mostly thorn-shaped, septa.
Halysites : Their representatives were widespread worldwide, but there are still no finds in South America. Their occurrence was in the Middle Ordovician to the Obersilur.
Pleurodictyum : This genus was distributed worldwide from the Lower to the Middle Devon. The special characteristic of this genus is the Hicetes , a worm that pierced the colony. Possibly it is a synecia , since the coral was obviously not badly damaged.
Favosites : They usually formed massive colonies with honeycomb-like calyx openings a few millimeters in diameter. They lived from the Upper Ordovician to the Middle Devonian.
Syringopora : This genus is often found inside fossil stromatopores, mostly in the genus Stromatopora . This is probably commensalism , the Syringopora apparently did no harm to the stromatopores.
literature
- Bernhard Ziegler: Introduction to Paleobiology. Part 2: Special paleontology, protists, sponges and coelenterates, molluscs. Schweizerbartsche Verlagbuchhandlung, Stuttgart 2004, ISBN 3-510-65036-0 .
- Ulrich Lehmann, Gero Hillmer: Invertebrates of prehistoric times: Guide to the systematic paleontology of invertebrates. Spektrum Akademischer Verlag, 1997, ISBN 3-432-90654-4 .
