Family Varanidae (Goannas/Monitor Lizards)
About thirty-six species occur throughout warmer parts of the 'old world' and about twenty-five of these occur in Australia. They are called monitors, or goannas, the terms being interchangeable.
These lizards are all of the typical lizard form and are usually medium-sized to very large lizards. The Komodo Dragon, the world's largest lizard, is a monitor, and Australia's largest lizards belong to this family. These Australian types may exceed 2 metres in length.
All monitors have well-developed teeth and larger ones can give a nasty bite. Goannas are the only Australian lizards to possess a forked tongue.
All types are strictly carnivorous, feeding on insects and other animals, depending on the size of the monitor. When well fed, the base of the tail often becomes thickened as a fat store, to be used in lean times.
All Australian monitors are placed in the genus Varanus, although they are sometimes placed within two sub-genera, one group with vertically compressed tails (Varanus) and another with tails that are round in section (Odatria).
Monitors are egg-layers. The eggs of most species take from three to twelve months to hatch.

The above was from the book Australian Reptiles and Frogs by Raymond Hoser and now available on a fantastic CD-Rom along with a vast amount of other information, papers and the like on reptiles, frogs and other wildlife.