Frenulina sanguinolenta Seashell Tropical Brachiopod Lamp Shell Brachiopoda

Frenulina sanguinolenta mm 9-11 Seashell Tropical Brachiopod Lamp Shell Brachiopoda, both valves.
Also available in lot of 5 pieces, at this link.
Family:  Frenulinidae.
Syn. Anomia sanguinolenta, Megerlia sanguinea.
Other species known: F. cruenta, F. mauiensis.

It should be noted for all bivalves that the two valves may have been glued or remained closed due to the dried ligament and therefore the item appears as a single piece. Therefore, we are not responsible for any damage caused to the shell to try to badly separate the pieces.

Frenulina is an existing genus of brachiopods, widespread in warm and shallow waters of the Pacific and Indian Ocean. Its shell is biconvex, with a rounded pentagonal profile, and with a lively scarlet color with sunburst stripes of variable width, beige or white. It lives attached to the seabed via a peduncle.
It is very common in the western Pacific, including Australia, New Caledonia, French Polynesia, the Philippines, China, Japan, and Hawaii, but is also found in the Indian Ocean.

The phylum of Brachiopods consists of marine invertebrates, benthic, sessil, sospensivorous and with bilateral symmetry. The plane of symmetry is perpendicular to the commissure of the valves, which are divided into a peduncular valve (or ventral) and a brachial (or dorsal), generally smaller. They are inequivalves and equilateral.
They look, similar to the phylum of bivalve molluscs, is simply due to convergent evolution, having no direct relationship with them.
Nowadays these animals are scarce because they live in "refuge areas", ie areas with low population and competition. They were however very common in the Paleozoic, then, following the mass extinction at the Permian-Triassic, have migrated into deeper waters.