Fossil range: Middle Cretaceous
Jaw bone of Koolasuchus.
| Scientific classification
Koolasuchus was a large Cretaceous amphibian that lived on the continent of Australia. It was a carnivo whose diet included turtles, clams and crayfish.
Koolasuchus was a member of the Temnospondyli order of amphibians and specifically of the Chigutisauridae family. It lived in the rift valley where southern Australia was starting to split from Antarctica, and perhaps elsewhere. It is notable both because it was one of the largest temnospondyls, and because it survived long after its cousins further north had become extinct.
Competition with phytosaurs during the Late Triassic, and later, crocodilians is believed to have contributed to the general decline of the temnospondyl order. At this point in time, Australia was within the Antarctic Circle, and had a climate too cold for crocodiles, protecting them from this competition. Koolasuchus could survive in this colder climate because, like modern salamanders, it is thought to have hibernated under the ice in ponds during the winter.
Koolasuchus shared with older temnospondyls a very wide, heavy skull (50 centimeters/20 inch wide) which contrasted with its small weak body and limbs. Like modern crocodiles, Koolasuchus had its eyes on the top of its head. This suggests that it was an ambush hunter. Around 5 meters (16 ft) long but only 30cm (1 ft) high, and with a weight of more than half a ton, it would have been able to hunt mammals or small dinosaurs who drank from the shallow swamps and rivers it lived in to supplement its diet. Due to its extremely large head and mouth, it may have been able to capture fish and shellfish by lying in wait and suddenly opening its mouth, sucking in water and its victim. This is a feeding style similar to that of the unrelated modern-day giant salamanders of Asia.
Koolasuchus was named in 1997 from the Aptian Strzelecki Group of the Wonthaggi Formation in Victoria. It is known from four fragments of the lower jaw and several postcranial bones, including ribs, vertebrae, a fibula, and parts of the pectoral girdle. A jawbone was found in 1978 in a fossil site known as the Punch Bowl near the town of San Remo. Later specimens were found in 1989 on the nearby Rowell's Beach. A partial skull is also known but has been fully prepared. Koolasuchus was named for the palaeontologist Lesley Kool. The name is also a pun on the word "cool" in reference to the cold climate of its environment. The type species K. cleelandi is named after geologist Mike Cleeland.