Why does Australia have so many venomous animals? | Live Science
Put another way, some already venomous species simply got stuck on Australia when it became an isolated landmass. Venomous arthropods there include trap-jaw ants (genus Odontomachus), which can inflict a painful bite; but these insects also live in other tropical and subtropical regions around the world, not just Australia. Similarly, Australian bulldog ants (genus Myrmecia), which can simultaneously sting and bite, are among the deadliest ants in the world and have reportedly killed three people since 1936, according to Guinness World Records. These venomous ant lineages were already on Gondwana at the time of separation and stayed there once Australia became its own continent.
As for spiders, funnel-web spiders (genera Hadronyche and Atrax) are the only exclusively Australian ones that can kill humans with a venomous bite, Arbuckle said. Male Sydney funnel-web spiders (Atrax robustus) are thought to have killed 13 people, although no human deaths have been recorded since antivenom was introduced in 1981, according to the Australian Museum. An Australian species of widow spider, the redback (Latrodectus hasselti), can also kill with a venomous bite. Their ancestors, too, predate Australia as a separate continent.
Likewise, venomous cephalopods, including squid, octopus and cuttlefish, have existed for up to 300 million years. They’ve lived in the surrounding waters for eras before Australia existed on its own.
Science evidently says it doesn’t really, support the idea that Oz harbors lots of venomous critters that is. But on this I’d go with popular opinion rather than the lizard lovers.