Bearded Dragons are one of the impressive Agamid lizards, and there's about 300 more fascinating species!
Agama lizards are Old World lizards. The Agamidae family consists of more than 300 species across six subfamilies. Agamid lizards include not only a large variety of Agamas, but also the very popular Bearded Dragons, Water Dragons and the Uromastyx, or Spiny-tailed lizards. There are also tree lizards, sailfin lizards, butterfly lizards and more.
There are many similarities between the Agamidae and the Iguanidae family. Agamas are considered the "Old World" equivalent of the Iguanidae family. The Iguanids are referred to as New World lizards because they are found on the American continents, while the Agamids are found on the "old world" continents of Africa, Asia, and Australia.
The lizards in the Agamidae family have well developed limbs, long tails, and often have bizarre forms such as crests, dewlaps and expandable appendages. The male agamids are often brightly colored. Many Agamids will breed easily in captivity, laying soft-shelled eggs in ground burrows.
The structure of the Order Squamata, and so too the Iguania Suborder and the Agamidae family, is being scrutinized and adjusted. Lizard taxonomy is a long, arduous process and the subject of much debate. Part of this re-classification is due to the discovery that more lizards are venomous than were previously thought.
It had long been thought that only the Gila Monsters and the Beaded lizards, in the Family Helodermatidae, were venomous lizards. But more recently it has been discovered that a couple other groups of lizards also contain venomous lizards including some in the Family Agamidae, like the Bearded Dragon. For pet owners there is no reason for undue concern, however, as the toxin secreting glands of these lizards are smaller than those of snakes. The venom they produce may aid to subduing small prey, but on a human it would have no effect, or very little. It is said that a bitten hand might throb at most.