Koolasuchus cleelandi was approximately 5 m (16 ft) long and 500 kg (1100 lbs). The large temnospondyl had an enormous head measuring about 65 cm (26 in) from snout to occiput. That head has been described a number o different ways, but it is most commonly depicted as possessing caudal facing lateral horns or as possessing a completely rounded head, like most modern salamanders. That enormous head was common in the Cretaceous rift valleys of Australia within the Arctic Circle. At that time Koolasuchus and its environment was subject to the long dark seasons of the extreme southern end of Earth. Koolasuchus and the dinosaurs it lived with were well adapted for these seasonal changes in different way. Though a hypothetical situation has been posed for this environment, the hibernation of Koolasuchus is based on similar cycles of extant salamanders. The fast moving streams in which Koolasuchus lived were ideal for crocodilian type predators, as Koolasuchus was hypothesized to have been. Unfortunately, its crocodile-like habits most likely led to its displacement and extinction as crocodilians, better at being crocodilians, took over their waterways and out competed Koolasuchus, replacing it in younger geographic strata.