Palythoa caribaeorum is a colonial zoantharian (family Sphenopidae, order Zoantharia) forming thick, encrusting mats on shallow Caribbean reef substrates, recognized as one of the most abundant and competitive space-occupying organisms on degraded Caribbean reefs. Its colonies incorporate sand and foreign particles into the coenenchyme, giving them a gritty, sandpaper-like texture. The species produces palytoxin and related compounds, among the most toxic marine natural products known. Genomic data have been generated for this species and are available in public databases, enabling comparative studies of cnidarian evolution and ecology.