Complex sentence: Hexabranchidae is a monotypic family of colorful nudibranchs (often called "sea slugs") which contains only a single genus "Hexabranchus", with two species, and has no subfamilies.
Split into simpler sentences: Hexabranchidae is a monotypic family of colorful nudibranchs (often called "sea slugs"). The family contains only a single genus "Hexabranchus", with two species, and has no subfamilies.