#notochord

• Lancelet — A small (a few centimeters), primitive marine vertebrate with a translucent, elongated body pointed at both ends, belonging to the phylum Cephalochordata. This structural organism represents an essential evolutionary transition link, as it retains the notochord, neural tube, and pharyngeal slits throughout its entire life, serving as a classic model in the study of comparative chordate anatomy.
• Amphioxus — The common or historical scientific name (genus Amphioxus) used in zoology to designate the lancelet (scientifically known as Branchiostoma lanceolatum), a small, translucent, lance-shaped marine invertebrate belonging to the Chordata phylum (subphylum Cephalochordata). It represents a fundamental reference organism in the study of comparative anatomy and vertebrate evolution, as it retains a simple structural dorsal notochord throughout its entire life cycle without developing a bony vertebral column.
• Amphioxus — A small marine animal with a translucent body, pointed at both ends, lacking a skull, vertebrae, and limbs, belonging to the chordate phylum, subphylum Cephalochordata (Branchiostoma lanceolatum). Structurally, the animal possesses a permanent notochord throughout its lifespan, representing a key link in the evolutionary study of vertebrate comparative anatomy.