Ostreoida

Pacific cupped oyster ( Crassostrea gigas ')'

The Ostreoida are an order of mussels ( Bivalvia ), which is provided infra class Pteriomorphia within the Autolamellibranchiata. It is a predominantly marine living mussel group. The oldest Ostreoida are known from the Triassic.

Characterization

The housing of the Ostreoida are almost always inequivalve and irregular. The shell is mainly kalzitisch. It consists of a foliated calcitic outer layer and inner calcite layers. In some forms still a thin aragonitic layer with kreuzlamellarer microstructure exist. Foot and byssus be reduced in an early post-larval stage. The castle is largely reduced, the ligament is usually external.

Way of life

The Ostreoida are mostly marine bivalve molluscs, the advance in brackish water areas. Only one group is also into fresh water. They are usually to the substrate or are cemented with the right or left door freely on the sediment. Often the fixed cemented molds form large colonies ( oyster beds ).

System

The Ostreoida contains two superfamilies with 6 families:

• Superfamily Ostreoidea Wilkes, 1810 Family oysters ( Ostreidae Wilkes, 1810)
• Family † Gryphaeidae Vialov, 1936
• Family † Palaeolophidae Malchus, 1990
• Family † Chondrodontidae Freneix, 1959
• Family † Eligmidae Gill, 1871

• Family † Lamellotidae Horvath, 1966

Previously the order was placed Pectinoida as a family to order Ostreoida.