Asteia

Asteia is a genus of extinct marine invertebrates belonging to the family Acrothoracica. These barnacles, characterized by their calcified shells, are known from fossils primarily found in the Cretaceous period. Asteia species were endolithic, meaning they bored into the shells of other marine organisms, such as mollusks and echinoderms, to create their dwelling. This lifestyle left characteristic boreholes in fossilized remains, serving as the primary evidence for their existence. The morphology of Asteia is understood through these boreholes and occasional preserved internal molds, which reveal details about their feeding apparatus and body plan. Their presence indicates a degree of host-parasite interaction, or at least a commensal relationship, within ancient marine ecosystems. The classification of Asteia within Acrothoracica places them alongside other burrowing barnacles, highlighting a significant evolutionary adaptation within the Cirripedia subclass. Research on Asteia contributes to our understanding of paleoecology and the evolution of sessile, filter-feeding organisms.