Inoceramidae

Inoceramus cuvieri

• Worldwide

The inoceramids ( Inoceramidae ) are an extinct family of mussels ( Bivalvia ) that is made to order Pterioida within the Autolamellibranchiata. It was an exclusively marine living mussel group. The oldest inoceramids you know from Lower Permian, the last species have become extinct at the Cretaceous - Tertiary boundary (KT - Impact).

Characterization

The housing of the inoceramids are always more or less equivalve, weak to strong inequivalve. In general, the left door is much more curved than the right door. The housing shape is variable, but usually roundish to oblong- oval. The front wings ( of Pterioida ) may still be relatively large, but almost absent. However, the rear wing is always present, but it is very different in size. Usually only concentric growth lines or ridges are present, rarely radial ribs. The relatively thick shell consists of an inner layer of aragonite, pearl ring microstructures and an outer calcitic prismatic and location. Under less favorable conservation conditions, the aragonitic layers can be dissolved away and disintegrate the calcitic layer into individual prisms. The castle is largely reduced, lock teeth are missing in almost all species. Also, the front sphincter is generally reduced more or less clearly. The ligament is broad and includes a plurality of ligament pits on. Most forms have a fine linen. Individual species of inoceramids can be considerably large (2 to 3 m length ).

Way of life

The inoceramids were an exclusively marine living mussel group, most of which were attached to hard parts on the seabed with the help of organic linen. They were apparently tolerant ( indicate findings in black shales ) against oxygen-poor environments. However, they are also found in a variety of other habitats of the continental shelf areas to the coast. For some species, a symbiotic relationship is discussed with chemotrophic bacteria. The species were most prevalent, sometimes even cosmopolitan and characteristic in the Upper Cretaceous only for relatively short periods of time.

Index fossils

Inoceramids primarily present in the Upper Cretaceous, due to the short time in geological sized periods occurrence of certain species and their long-range geographical diffusion, important index fossils. Inoceramus crippsi occurs in the Cenomanian, I. and I. labiatus lamarcki are conductive in the Turonian. The end of the Turoniums is defined by the onset of Cremnoceramus rotundatus.

System

• Superfamily † Ambonychioidea Miller, 1877 and Family † Inoceramidae Giebel, 1852 Inoceramus Sowerby, 1814
• Birostrina Sowerby, 1821
• Cremnoceramus Cox, 1969
• Mytiloides Brongniart, 1822

And about 20 other species. The system is z.T. still fragmented. Many species are regarded by some authors only as a subgenus of Inoceramus or completely rejected.