What is the function of a lamp shell’s pedicle?

The pedicle of a lamp shell (phylum Brachiopoda) primarily serves as a structure for attachment to a substrate, such as pebbles, stones, or other hard objects.12

Its specific function can vary depending on the type of brachiopod:

• Attachment: Many hinged (articulate) brachiopods use a tough, fibrous pedicle to anchor themselves firmly to a surface.1
• Burrowing and Movement: In the inarticulate genus Lingula, the pedicle is long, fleshy, and flexible. It aids the animal in burrowing into mud or sand and keeps it anchored at the bottom of its burrow. This contractile pedicle also allows the animal to extend its shell to feed or retract it quickly if startled.1
• Rotation: Muscles extending from the pedicle to the dorsal valve allow the animal to rotate its shell on the pedicle.1

In some specialized species, the pedicle may be atrophied, causing the shells to lie loose on the sea floor, or the animal may be cemented directly to the substrate by the beak of its ventral valve.1