Agnostida
| Agnostida | ||||||||||||
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The trilobite Peronopsis interstrictus from the order Agnostida |
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| Temporal occurrence | ||||||||||||
| Lower Cambrian to Upper Ordovician | ||||||||||||
| 542 to 443.7 million years | ||||||||||||
| Locations | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Agnostida | ||||||||||||
| Salter , 1864 |
The Agnostida are one of the currently nine recognized orders of the trilobite class . They were small to very small trilobites, mostly only a few millimeters in length, with a head shield ( cephalon ) and tail shield ( pygidium ) very similar in shape , typically often rolled up.
The head shield is usually almost circular and often corresponds in shape and size to the tail shield, so that at first glance you do not always see what you have in front of you, the head or the tail. Often no skin seams can be seen.
Occurrence
These small trilobites are typical of the Cambrian . Agnostine species occur up to the Upper Ordovician .
Submissions
This order has two subordinates: Agnostina and Eodiscina . The agnostines always have a two-part thorax and always no eyes. The Eodiscina usually have a tripartite thorax and usually the eyes are absent.
See also
Individual evidence
- ↑ a b Heinz Kowalski, Trilobiten: quick-change artist of the Paleozoic; an unorthodox foray through the realm of the Dreilappers , Goldschneck-Verlag Werner K. Weidert, Korb, 1992, ISBN 3-9261-2912-3
