EOSC 326 Study Guide - Bivalve Shell, Brachiopod, Lophophore
3 May 2012
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Polar regions: symmetry: contains two shells/valves, brachiopods are equilateral but inequivalved. The cardinal process is a projection at the posterior edge of the dorsal valve where the diductor muscle is attached. Brachiopods: history, inarticulata: no hinge with a tooth and socket system exists, the valves are held together purely by muscles. A pedicle protrudes from a hole on the ventral valve called pedicle foramen, and attaches to the substrate. The second valve forms a cap on top of the cylindrical valve. This group formed an important part of the. Pedicle is lost and the foramen is sealed off. Their large size (15- 30cm) requires spiral- shaped brachidia to support a larger lophophore. Ordovician to jurassic: burrowing: only one species in this group, the lingulids. They live in sandy/muddy substrates, burrowing head- first, then making a u- turn and coming back out the substrate. The animal attaches to the substrate by mucus on its pedicle.
