Bursiidid

Bursiidid is a family of marine gastropod mollusks, commonly known as helmet shells or tun shells. These snails are characterized by their large, globular, and spirally coiled shells, which are often smooth and glossy, though some species exhibit ornamentation like knobs or ribs. The aperture of the shell is typically wide and ovate, with a smooth inner lip. Bursiidid species are found in tropical and subtropical waters worldwide, inhabiting sandy or rocky substrates on continental shelves and coral reefs.

The diet of bursiidid snails consists primarily of echinoderms, such as sea stars and brittle stars, which they capture and consume using their radula. They are generally slow-moving and are often found partially buried in sediment or hidden amongst rocks. Reproduction in bursiidids typically involves external fertilization, with females laying egg masses that are attached to the substrate. The larval development varies among species, with some exhibiting planktonic larvae and others direct development.

The family Bursiidid contains several genera, including Bursa, Colubrellina, and Crossata. Some species, like Bursa bufonia, are notable for their size and distinctive shell morphology. While not typically a significant commercial species, some bursiidid shells are collected by hobbyists and for decorative purposes. Their ecological role as predators of echinoderms is important in maintaining the balance of their marine ecosystems.