KINGDOM: Animals

Bilaterally symmetrical animals

SUPERPHYLUM: Deuterostomes

PHYLUM: Chordates

SUBPHYLUM: Vertebrates

INFRAPHYLUM: Gnathostomes

TELEOSTOMES

EUTELEOSTOMES

CLASS: Sarcopterygians

RHIPIDISTIA

SUBCLASS: Tetrapodomorphs

SUPERCLASS: Tetrapods

Tetrapoda are vertebrates with four limbs and therefore include amphibians, reptiles, birds and mammals.

Evolution has promoted tetrapods into a superclass to accommodate the vast array of animals that have evolved in the last 365 millions years from this categorisation.

Tetrapods were originally completely aquatic animals, but lived in freshwater environments.  Due to their advanced lung and limb development, they were able to survive in very shallow water conditions such as swamplands.

Features of early tetrapods were the development of elbows and knees in their fins.  These fins were now becoming increasingly versatile in the tetrapods ability to paddle through shallow waters and to move along underwater surfaces.

The development of tetrapods must have been considerable.  Tetrapods developed as their requirements to venture out of water and onto land increased.  However, before they could do so they would have had to have developed a sturdy enough skeleton to support their body weight, else their weight out of water would have crushed their internal organs.  Also it is thought that ear development would have had to have taken place to be suitable for life above the water's surface.  It is thought that their limbs would have developed a digit structure at their tips during this period also.

Over time the original tetrapods have developed primarily into batrachomorpha and reptiliomorpha.

Batrachomorpha contain all extant species of amphibians and their ancestral extinct relations which are certainly not among the reptiliomorpha.

Reptiliomorpha is normally only used to refer to the genera of extinct animals which preceded the amniota, which is the series of animals that contain modern day reptiles, birds and mammals.  Although the original reptiliomorphs are described as being amphibious.

However, there are a number of extinct species of animal that have been discovered in a fossilised condition which have been categorised as tetrapods, but are believed to be too primitive to class as batrachomorpha or reptiliomorpha.

These extinct species are within the families elginerpetontidae, acanthostegidae, ichthyostegidae, tulerpeton, crassigyrinidae, loxommatidae, colosteidae, whatcheeriidae and diadectes.  Another extinct species which belongs alongside these families is hynerpeton.

Humans have evolved from reptiliomorpha.