(1) Tetrapods are part of a larger groups called Sarcopterygii, which also includes several groups of lobe-finned fish, such as lungfish and the coelacanth .

(2) Fossil coelacanth were found only a few years ago in a shale-bed near Grahamstown, relics of a silent world which existed before birds or mammals, seed-bearing or flowering plants.

(3) Little changed over the past 500 million years, the chambered nautilus is considered a ‘living fossil’, like the horseshoe crab and the coelacanth .

(4) In most fossil coelacanths , the swimbladder appears to be ossified and, consequently, these fishes were probably confined to shallow water.

(5) They were hit hard by the terminal Devonian extinction event, and most marine forms died out then, only the coelacanths continuing.