"These molecules represent a tremendous, hitherto unexplored resource for utilisation in drug design," he said. Goannas are monitor lizards, a group which includes the Komodo dragon.

Dr Fry said that because these carnivores fed on carrion in the wild, toxic bacteria in their mouths had long been blamed for the pain, swelling and prolonged bleeding caused by bites. His suspicions were alerted, however, when he saw a zookeeper in Singapore develop symptoms rapidly after being bitten by a captive Komodo dragon which had been brought up on fresh food. "It didn't sit right with me; bacteria don't work that fast," Dr Fry said.

When he studied an Australian lace monitor, or common goanna, the closest living relative of a Komodo dragon, he found a huge gland running down the side of its jaw. Squeezing it released the venom. "You could see it pooling at the base of the teeth. It's amazing what you find when you look."

His international team, which includes researchers from Monash University, has identified nine types of toxins from lizard venom which snakes also produce. One toxin found in the venom of the bearded dragon, one of the most popular pet lizards in the world, had previously been identified only in rattlesnake venom. However, Dr Fry said goanna lovers need not be alarmed, because the venom in these lizards was not present in amounts large enough to cause serious harm. Unlike snakes, lizards do not have fangs to inject venom into their prey. The research, which is published today in the journal Nature, suggests venom systems in reptiles evolved only once, and much earlier than had been thought - about 200 million years ago - in a common ancestor of snakes and lizards.

The team also found iguanas produced venom. Before the study, only two species of lizards from North America, the Gila monster and the Mexican beaded lizard, were known to produce venom and it had been thought they evolved this ability independently of snakes. Dr Fry, who has previously worked with highly venomous snakes, said he enjoyed being able to relax while studying goannas. "They're beautiful animals," he said.

Last week he was awarded a $145,000 Australian Research Council grant to study lizard venom. Venom from lace monitors has already been found to have a strong effect on blood pressure and blood clotting.