Brachiopod File

Unlike bivalves (clams), where shells are mirror images of each other, brachiopod shells are top/bottom oriented and distinct, but each individual valve is symmetrical down the middle.

They were the most common shelled macroinvertebrates in the Paleozoic era. brachiopod

They resemble ancient Roman oil lamps, especially the Terebratulida order. Unlike bivalves (clams), where shells are mirror images