Down Under Dragons

Some giant monitors that roam(ed) Australia.

 Varanus giganteus - Perentie

The largest modern Varanid in Australia. With an average length of about 2 meter and a maximum size of 2,5 meters it's quite a huge reptile already, but it gets beaten by water monitors, crocodile monitors and Komodo dragons in terms of size. Also they are quite slender in build which makes them good speedsters. They're good diggers too and have the habit of standing on their hindlimbs in tripod stance to have a better look of their surroundings. They also have a beautiful colour pattern.
In Dutch they're called "reuzenvaraan" which means "giant monitor lizard". A literal translation of the scientific name, but sadly, when perenties were named, we hadn't yet discovered the biggest lizard of today...

 Varanus komodoensis - Komodo dragon

A maximum size of 3,1 meters and a maximum weight of over 150 kg, osteoderms beneath its skin and a venomous bite*.
Komodo dragons are the largest lizards of today and are only found on a handful of Indonesian islands. However they originated on mainland Australia and spread westwards through time. 300 000 years ago they went extinct in Australia.
They aren't a result of insular gigantism as was once thought, they were already huge when they arrived on islands such as Flores. I also heard they were actually larger on Australia which makes them a case of insular dwarfism, but can't find any sources for that. If somebody knows more, feel free to comment about it. If not, don't take that last sentence as truth yet.

 Varanus priscus - "Megalania"

First known as Megalania prisca and later renamed, but everyone knows this guy as Megalania so I guess it makes a good common name.
The largest lizard ever with size estimates running up to 7 meters. However, I'm going to stick with a more conservative estimate of about 5 meters. Notice the little crest on its skull.
Megalania lived together with Komodo dragons and perenties for a while, hunting the megafauna of Pleistocene Australia before going extinct some 40 000 years ago after Homo sapiens arrived. In contrary to what some might believe it isn't possibly still alive.
Also, since this thing very likely was venomous it was the largest venomous animal to have ever lived.



*A 2006 study talks about the discovery of venom toxins in Varanidae and Iguania which means their venom had an early origin basal for snakes, iguanians and anguimorphs because those form a clade together.

Now I haven't found a phylogenetic tree yet for Mosasauridae in Squamata, but since those things are close to monitor lizards... giant venomous marine reptiles, anyone?