Pentamerida

The Pentamerida were an order of brachiopods, which are marine invertebrates commonly known as "lamp shells" due to their resemblance to ancient Roman oil lamps. These organisms possessed two shells, or valves, and were abundant during the Paleozoic Era, particularly in the Silurian period.12

Key characteristics of Pentamerida include:
* Biconvex shells, meaning both valves bulge outward.1
* A spondylium, which is a fused pair of dental plates, typically found in the ventral valve.1
* An open delthyrium, the opening for the pedicle (a stalk-like organ for attachment).1
* Brachiophores (supporting structures for the lophophore, a feeding organ) in the dorsal valve that are supported by bracing plates.1
* Impunctate shells, meaning they lack pits.1

While once widespread, the Pentamerida flourished in the Ordovician and Silurian periods but declined and became extinct early in the Late Devonian period.1