Protobranchia

Acila cobboldiae

The Protobranchia or Protobranchiata ( Urkiemer ) are a large group of bivalves (mussels ), which is conducted in the newer classifications as a class, subclass or class infrastructure. It is a relatively small shell group. She is a sister group to Autolamellibranchiata ( Eigenblattkiemer ), which includes the vast majority of Muscheltaxa.

Characterization

The housing of the Protobranchia are relatively small and mostly equivalve. The shells are aragonitisch with a mother of pearl ply and sometimes a layer of homogeneous microstructures, which are then overlaid with the organic periostracum. The castle was originally taxodont, in a few derived forms also toothless. As derived and thus apomorphic applies a special larval form, a peculiarity in the stomach ( without solid crystal stem ) and the palp - Probosciden to the labial palps (mouth buttons ). The ligament is external or internal, the most representative of the Protobranchia are isomyar, ie the two sphincters are approximately equal, few forms of unequal sphincters. The gills are proto branch, which probably represents the original state of the gills in the shells.

System

The Protobranchia are in cladistics, the sister group of the Autolamellibranchiata. The Protobranchia appear as Infra class, subclass or as a taxon without rank in the classifications. They are best classified as part -, infra - or subclass. The Protobranchia include two or three orders, the order Nuculanoida has recently been set up and has not yet found general acceptance. Show the relationship between the three systems is not yet secured, and so no further subdivision is necessary.

Protobranchia Pelseneer, 1889

• Order Nuculoida Dall, 1889 Superfamily † Fordilloidea POJETA, 1975
• Superfamily Pristiglomoidea Sanders & Allen, 1973
• Superfamily Nuculoidea Gray, 1824
• Superfamily † Ctenodontoidea Wöhrmann, 1893

• Superfamily Solemyoidea Gray, 1840
• Superfamily Manzanelloidea Chronic, 1952

• Superfamily Nuculanoidea Adams & Adams, 1854