Discoplastis spathirhyncha is a disc-shaped marine dinoflagellate with armored cells composed of cellulose thecal plates arranged in a specific pattern for structural support and protection. It possesses two flagella of unequal length; one extends backward into a groove called the sulcus, while the other flagellum is free and extends outward, enabling motility. The cell contains a centrally located nucleus and is photosynthetic, housing chloroplasts that utilize chlorophyll and other pigments to capture light energy for photosynthesis. This species inhabits tropical and subtropical marine environments, contributing to marine ecosystems through its photosynthetic activity and adaptability to varying environmental conditions.