The Komodo Dragon (varanus komodoensis) is, as every schoolchild knows, the coolest lizard in the world, the next best thing to a real live dinosaur.
First discovered by Western science on the island of Komodo in Indonesia in the early 20th century, there are only about 6,000 Komodo Dragons alive today, their habitat restricted to a few Indonesian islands (Flores, Komodo, Gili Motang and Rinca) where the local name for them is ora. They are also sometimes referred to as buaja darat (land crocodile), though this is inaccurate as they are true lizards, not crocodilians. Up to the 1970's they could also be found on the island of Padar.
Komodo Dragons belong to the family Varanidae, which includes over 50 species of monitor lizard, of which they are the biggest. In fact, at up to ten feet long when fully grown, they are the biggest lizards in the world, and can weigh over 500 pounds. The females are smaller and lighter, with an average adult length of about 7 feet and weighing 150 pounds. They are mostly black, green or gray, with patches of yellow, brown or white. They can live for up to 50 years in the wild, though most of them don't make it past childhood.
Komodo Dragons are accustomed to a hot climate, and have been found in environments ranging from open, dry grassland to rain forest. For the first couple of years of their life they live in trees as a safeguard against being eaten by others of their own kind, surviving mostly on insects and geckos. Adults will eat practically any kind of meat, including that of younger dragons, and frequently scavenge the kills of other predators, but they are just as capable as hunters, and their most popular prey is the Sunda deer.
As hunters, these lizards are badass. A Komodo Dragon can run faster than many humans over short distances, and they do not need to finish their prey quickly - their mouths contain over 50 types of toxic bacteria, 7 of which can cause severe blood poisoning. Usefully, however, their bites are not poisonous to other komodo dragons. They can smell carrion at distances of 6 to 7 miles due to Jacobsen's Organ, an olfactory enhancement in the roof of their mouths. Due to competition at mealtimes, Komodo Dragons have developed a tooth structure that is more commonly seen in sharks than lizards, and can consume 80% of their own body weight in one sitting, sometimes in less than half an hour, after which it will not need to eat again for about a week. They are also good swimmers, and can catch fish. Uniquely for a lizard, it is at the top of the food chain in the islands it inhabits.
Severely endangered, the Komodo Dragon is an internationally protected species, but can fetch as much as $30,000 on the black market, for anyone foolhardy or rich enough to want to own such a dangerous pet. However, they are more in danger from the reduction of their natural habitat than from hunting. Also, there is regular hurricane and volcanic activity in the vicinity of their islands, which stresses the fragile ecosystem even more. Komodo National Park was created in 1980 to protect most of their natural hunting range, but it is not known whether their numbers are increasing.
It is thought that the dragons were left isolated in their island habitats by retreating ice at the end of the last ice age - a much larger, almost dinosaurian species, Megalania prisca was alive in Australia as recently as 25,000 years ago. This super-lizard reached lengths of up to six meters, and humans may have encountered it (or even caused its extinction). There are even persistent, though rare, contemporary reports of encounters with giant lizards deep in the outback, and some people think Megalania prisca may still be alive in certain remote regions.
Update: It appears due to a recent case (21st December 2006) that Komodo Dragons share a somewhat rare but well-documented ability of certain lizards to self-fertilize and therefore reproduce asexually. Parthenogenesis has been recorded in many lizard species but never among the dragons, and due to their currently-endangered status, this discovery has made conservationists quite happy. It also made the papers very happy, since the story was splashed a few days before Christmas with headlines such as "Virgin to give birth" and "Dragon Virgin's Immaculate Conception". One version of the story, from MSNBC: http://www.msnbc.msn.com/id/16298548/