Atrypida
| Atrypida | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Atrypa reticularis (Linnaeus, 1758) |
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| Temporal occurrence | ||||||||||||
| Ordovician to Jurassic | ||||||||||||
| 470 to 145 million years | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Atrypida | ||||||||||||
| Gill , 1871 |
Atrypida (atrypids) are an extinct taxon of arm pods (Brachiopoda) with a short, straight or curved lock rim, a mostly impunctate shell and a differently oriented spiral (= helicopegmate) arm structure. The interarea of the ventral valve (= pedicle valve) is small or missing. Together with the Protorthida , Orthida , Rhynchonellida , Pentamerida , Spiriferida and Terebratulida , they form the taxon Rhynchonellata , which in turn belongs to the sub-strain of the Rhynchonelliformea .
features
The stem opening is often located in the vertebra. The small or non-existent interarea in the ventral valve is characteristic. The spiral arm structure is oriented differently. In the history of the earth they occur from Ordovician to Jura .
Systematics
The atrypids are divided into five sub-taxa, which are subdivided according to the orientation and shape of the arm framework (and the jugum):
- Atrypacea arm spirals to the median line or obliquely to the dorsal side, simple Jugum (Ordovician to Devonian)
- Dayiacea arm spirals sideways or diagonally anteriorly or plane spiral parallel to the median line, jugum simple or absent (Ordovician to Devonian)
- Athyridacea arm spirals sideways, complicated jugum (Ordovician to Triassic)
- Konickacea arm spirals ventrally, complicated Jugum (Triassic to Jurassic)
- Retziacea arm spirals sideways, usually punctate shell (Silurian to Triassic)
literature
- Bernhard Ziegler: Introduction to Paleobiology Part 3 . ISBN 3-510-65179-0
- Treatise of Invertebrate Paleontology: H (Brachiopoda revised) 2 . ISBN 0-8137-3108-9
- Ulrich Lehmann, Gero Hillmer: Invertebrates of the past . ISBN 3-432-90653-6
