Pteriomorphia

Pteriomorphia is a subclass of bivalve mollusks, characterized by their hinged, two-part shells. The term "pteriomorphia" is derived from the Greek words "pteron," meaning wing, and "morph," meaning form, reflecting the wing-like shape of the shell valves. This subclass includes a diverse range of species, from small, microscopic forms to large, commercially important ones.

The shells of pteriomorphs are typically asymmetrical, with one valve being larger and more convex than the other. The hinge is located on the posterior (rear) side of the shell, and it is composed of a series of plates that articulate with each other. The shells are often covered by a thin, calcareous layer, which can be smooth or ornamented with various patterns.

Pteriomorphia is further divided into two main groups: Heterodonta and Homodonta. Heterodonta, or true clams, have a hinge with a single, central ligament, while Homodonta, or true oysters, have a hinge with two lateral ligaments. Both groups exhibit a wide range of ecological adaptations, from filter feeders in marine environments to burrowers in freshwater habitats.

The subclass Pteriomorphia is of significant ecological and economic importance. Many species play crucial roles in marine ecosystems, serving as food sources for various predators and contributing to sediment stabilization. Additionally, several species are commercially valuable, including oysters, clams, and scallops, which are harvested for food and used in aquaculture.