Brachiopoda

Unlike bivalve mollusks (clams), brachiopod shells are symmetrical across a vertical plane (between the valves) rather than a horizontal plane.

Lingula (an inarticulate) is considered a "living fossil," remaining virtually unchanged for over 500 million years. IV. Evolutionary History and Paleontology brachiopoda

Lack complex hinges, held together by muscles. Unlike bivalve mollusks (clams)

Composed of calcium carbonate (articulates) or calcium phosphate and chitin (inarticulates). brachiopoda

Fewer than 500 species exist today compared to thousands in the fossil record, marking a massive decline in their ecological importance. VI. Conclusion

Brachiopods are marine, benthic, sessile filter-feeding invertebrates with a two-part shell (bivalved).