Radiolitids

Radiolitids were a family of extinct bivalve mollusks that lived during the Cretaceous period. They are characterized by their distinctive, often conical shells, which were typically cemented to the substrate. The outer shell was composed of radial prisms of calcite, giving them their name. Radiolitids were epifaunal, meaning they lived on the surface of the seafloor. They were widespread and abundant in shallow marine environments across the globe. Their large, robust shells suggest they were well-adapted to turbulent conditions. Fossilized radiolitids are important index fossils for dating Cretaceous rock formations. Economically, some radiolitid deposits have been explored for potential building materials due to their abundance and structure. Their evolutionary lineage is traced back to earlier rudist bivalves, and they themselves represent a highly specialized group within this clade. The extinction of radiolitids, like many other Cretaceous organisms, is linked to the K-Pg extinction event.