Protochordates

A solitary sea squirt

The name Protochordates literally means 'the first chordates.' The chordates include fish, amphibians, reptiles, birds and mammals.

The protochordates fall into two broad groups or subphyla - the Urochordata and the Cephalochordata.

Urochordata

The urochordata includes the group known as the tunicates - animals whose free-swimming larvae have a notochord* and a nerve chord. The adults are sessile - that is to say they are anchored to one place on the Reef.

Cephalochordata

Cephalochordates, or lancelets, are fish-like animals that have a notochord and nerve chord along the entire length of their bodies and which persist all their lives.

* A notochord is a an elongated cellular chord enclosed in a sheath, that forms the primitive skeleton of chordate embryos (including humans) and adult cephalochordates.