Graptolites
| Graptolites | ||||||||||||
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Fossil plate with Didymograptus murchisoni from the Ordovician . |
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| Temporal occurrence | ||||||||||||
| Upper Cambrian to Viséum ( Carbon ) | ||||||||||||
| 513 to 345 million years | ||||||||||||
| Locations | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Graptolithina | ||||||||||||
| Bronn , 1849 |
The Graptolites ( font stones ) are an extinct class polyps Similarly , colony-forming marine animals, commonly in the gill hole animals are classified (Hemichrodata).
Only the residential tubes that have a chamber structure have been passed down fossil . The hemichore relationship results from histological investigations and is so close that some researchers (such as Vladimir N. Beklemischew ) regard the pterobranchia as surviving graptolites. After the discovery of the pterobranch Cephalodiscus graptolitoides , which was found at great depth near New Caledonia , other scientists are of the opinion that the graptolites must be classified in the pterobranch, since the fossilizable parts of Cephalodiscus graptolithoides are confusingly similar to a graptolite, while the living one Organism is an ordinary pterobranch.
The lifestyle of Graptolites was early in their evolutionary history sessile - benthic . Continuing their evolution developed planktonic species. The construction of the graptolites showed growth along one or more axes. Depending on whether the living chambers (counters) were arranged in single or multiple rows along the axes, a distinction is made between monograptids (1 row), diplograptids (2 rows) or phyllograptids (4 rows). The colonies had one or more axes with straight or curved growth forms.
The possibly unique structural protein (scleroprotein, structural protein) of this group of animals is graptin. It is similar in structure to chitin . It was first described in 1973 by Roman Kozłowski .
Due to the rapid development of the class over time, their wide distribution and the macroscopically easily recognizable fossils, the graptolites are excellent reference fossils from the Upper Cambrian to the Lower Devonian . Graptolites are mainly found in slate (graptolite slate).
Systematics
The graptolites are divided into six orders:
Individual evidence
- ^ Hynek Burda , Gero Hilken, Jan Zrzavý: Systematic Zoology. UTB, Stuttgart; : 1st edition 2008, page 225, ISBN 3825231194
- ^ Ulrich Lehmann : Paleontological Dictionary . 4th edition. Ferdinand Enke Verlag, Stuttgart 1996, p. 100 .
Web links
Thallograptus sphaericola
Pendeograptus fruticosus
Amplexograptus
