These muscles pull the dorsal beak forward, rotating it on a line joining the hinge teeth.
Slow components of the adductor muscle permit sustained adduction, while the interlocking hinge teeth prevent shear.
The mantle lobes secrete the shell valves; the mantle crest secretes the ligament and hinge teeth.
Several species of brachiopod have been found in the Latham Shale, including some of the earliest articulate brachiopods (brachiopods with hinge teeth) known from the fossil record.
Paleontologists interpret bivalves on the basis of shell features, notably shell and ligament structure, arrangement of hinge teeth, and body form as interpreted from internal muscle scars.
Along the hinge line of the shell there are in most cases a number of hinge teeth which prevent the valves from moving laterally relative to one another.
Teleodesmacea on the other hand have a porcelanous and partly nacreous shell structure; Mantle lobes that are generally connected, well developed siphons, and specialized hinge teeth.
Prionodesmacea have a prismatic and nacreous shell structure, separated mantle lobes, poorly developed siphons, and hinge teeth that are lacking or unspecialized.
R.C. Moore, in Moore, Lalicker, and Fischer, 1952, Invertebrate Fossils, gives a practical and useful classification of pelecypods (Bivalvia) even if somewhat antiquated, based on shell structure, gill type, and hinge teeth configuration.
[ Lower Ordovician – Recent] Pachydonta: Large, different, deformed teeth (e.g. rudist spp .. [ Late Jurassic – Upper Cretaceous] Desmodonta: Hinge-teeth absent or irregular with ligaments (e.g. family Anatinidae).
