Crocodilia includes all crocodiles, alligators, and gharials. There are 23 species of extant crocodilians of which 8 species have been known to attack humans. The biggest two species, are the nile crocodile and the estuarine crocodile which are suspected of growing up to 7 metres long and weighing up to 1500kgs. The largest ever crocodile to be captured and accurately measured was an estuarine crocodile measuring 6.17m and 1075kgs which was caught in the Philippines. Larger unofficial crocodiles of both the large species have captured and or killed in the past. The difference between crocodiles and alligators is that there are teeth exposed from both jaws of a crocodile when it has its mouth closed whereas alligators only have teeth of the upper jaw exposed.
Australia has two species of crocodile, the large estuarine crocodile (Crocodylus porosus) and the smaller Australian freshwater crocodile (Crocodylus johnstoni)