Lancelet

 Scientific Name: Branchiostoma sp. (Amphioxus sp.)

Classification

Phylum: Chordata -Dorsal tubular nerve cord, gill-slits and notochord present.

Subphylum: Cephalochordata -Notochord along entire body length and persistent.

Habit and Habitat: Branchiostoma burrows in clean shifting and shallow shore waters leaving only its anterior end protruded. Most of the time, it remains buried in the sand but in darkness, it swims very rapidly by lashing movements of the tail. It is a ciliary feeder.

Characteristics 

1. The adult is less than 5 cm long and has superficially fish-like structural make-up.
2. The body is elongated, flattened, non-pigmented and pointed at both ends as the name implies. Anterior end projects forwards as the rostrum.
3. Dorsal, ventral and caudal fins are low and continuous. There are 2 lateral fins or metapleural folds. The dorsal fin has fin rays.

Video

Chordate Animation - Amphioxus to Vertebrate Body Plan. Source: YouTube, Shape of Life

References

• Practical zoology vertebrates by S.S Lal
• The life of invertebrates by J.Z Young