Protobranchia


Protobranchia is a subclass of bivalve molluscs. It contains the extant orders Nuculanida, Nuculida, and Solemyida.
These are deep water clams of a small and primitive order with a taxodont hinge, generally with a central ligament pit, large labial palps which are used in deposit feeding and the gills used only for respiration, the anterior and posterior adductor muscles are nearly equal in size, a foot which is divided sagittally and longitudinally with papillate margins. The foot in Protobranchia clams is without a true byssus gland, although they frequently have a nonhomologous byssal gland in the heel. The byssal gland in these clams does not produce threads as in Pteriomorphia.

2010 Taxonomy

In 2010 a new proposed classification system for the Bivalvia was published by Bieler, Carter & Coan revising the classification of the Bivalvia, including the subclass Protobranchia.
'''Subclass: Protobranchia'''

Order: [Nuculanida]

Source:

Order: [Nuculida]

Source:

Order: [Solemyida]

Source:

Order: † [Praecardiida]