KINGDOM: Animals

Bilaterally symmetrical animals

SUPERPHYLUM: Deuterostomes

PHYLUM: Chordates

The phylum called chordata generally contains animals described as vertebrates (animals with a spine) apart from some exceptions which would have had a major chord within their body at some stage of their development.

Chordates are understood to have a notochord and a dorsal neural tube which in vertebrates develop into a spine and a spinal chord.

Chordates are supposedly equipped with a pharynx which filters consumable materials from expellable water.  The pharynx is typically in the back of the throat.

Chordates also have a muscular tail at some part of their development.

There is a lot of speculation regarding various fossils discovered in the Far East dating as far back as 542 million years ago as to the original development of chordates, which includes confusion as to whether certain fossils are chordates or hemichordates.

Chordates have been split into three subphyla, namely vertebrata, cephalochordata and tunicata.

Vertebrates are distinguished by their backbones and spinal columns and make up many of the world's fish, birds, reptiles, amphibians and mammals which are familiar to many in zoos.  So it is advisable to anyone wishing to find out more regarding such animals that they skip to this section as the rest of this section deals solely with other chordates.

Cephalochorata are represented in the modern world by the lancelet.  Many researchers are fascinated by the lancelet as they view it as a unique animal which provides the link between cephalochorates and vertebrates believed to date back 520 million years.  The difference between the lancelet and a vertebrate is that the notochord extends to the head in the lancelet.

Tunicates are underwater chordates.  Many spend their mature life anchored to the ocean floor or rocks, absorbing seawater or feeding on nearby tiny animals.  Some tunicates live away from the ocean floor, but in general you would have no idea that these animals are so closely related to other chordates.

A special mention must be made at this stage to the hagfish.  The hagfish is a craniate (a chordate with a definite cranium), and it is generally understood that all craniates are vertebrates.  However, the hagfish is not recognised as a vertebrate in that it doesn't have a spine.  This makes the hagfish quite unique.  Hagfish belong to the class called myxini which is the distinguishing class of animal just decribed.

Humans are vertebrates.