Antipathozoanthus obscurus is a zoantharian coral (order Zoantharia, family Antipathozoanthidae) known to grow epizoically on the axes of antipatharian (black coral) colonies—a commensalistic or parasitic relationship unique among cnidarians. It is found in deep-water environments in the Caribbean and tropical Atlantic. The Antipathozoanthidae is a recently recognized family defined partly on the basis of molecular phylogenetics. Genomic data have been generated for this species and are available in public databases, enabling comparative studies of cnidarian evolution and ecology.