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Atrypa reticularis (Linnaeus, 1758)

Atrypa reticularis (Linnaeus, 1758)

Temporal occurrence
Ordovician to Jurassic
470 to 145 million years
Primordial mouths (protostomia)
Lophotrochozoa (Lophotrochozoa)
Arm pods (Brachiopoda)
Scientific name
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 .


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 .


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)


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