Isognomon


Isognomon is a genus of marine bivalve mollusks which is related to the pearl oysters.
Isognomon is known in the fossil record from the Permian period to the Quaternary period. Fossils of species within this genus have been found all over the world.

Taxonomy

This genus was formerly placed in the family Isognomonidae, however molecular phylogeny studies have shown that these tree oysters belong in the family Pteriidae.

Description

These oysters grow to be about in overall length, producing a highly irregular shell with a blue-gray and often heavily encrusted exterior but a smooth and pearly white interior. They use their byssus to completely immobilize themselves to the roots of mangrove trees, corals, and other substrates. It is because of the preference for mangroves that these are sometimes called tree oysters

Species

Extinct species within this genus include:
;Species brought into synonymy: