Kronosaurus was one of the ocean reptiles known as pliosaurs a member of the plesiosaur group, but in the Pliosauridae relations, with the characteristic feature of a much shorter, thicker neck.
It lived during the premature Cretaceous period.
Pliosaurs were more heavily built, more streamlined, sooner and fiercer than other plesiosaurs and were suited to catch fewer, bigger meals with their massive jaws and rows of sharp teeth up to 25 cm (10 inches) long. They had a huge head, which was mostly mouth and it also had great eyes and an offset pair of nostrils that gave it directional water-sniffing capability, as in other plesiosaurs.
Kronosaurus was a carnivore with a head that was up to 9 feet (2.7 metres) long, about a third of the whole length of the body.
Kronosaurus lived in the open oceans and breathed atmosphere. Some Plesiosaurs have been found with little stones in their stomachs which may have been used to help grind up their food, or as ballast, to help them dive. They possibly laid eggs in beach sand (like contemporary sea turtles).
Kronosaurus swam with all of its four limbs, which had evolved into long, wide, burly flippers, one at each bend of the elongated body. The tail was small and tapering, as in other plesiosaurs and was perhaps used only for navigation.
Kronosaurus was one of the biggest pliosaurs and lived in the Early Cretaceous Period. The majority of its fossils are known from Australia, where they were first discovered in 1889 in Queensland, which was covered by shallow ocean some 120 million years ago.
The total length of a Kronosaurus was up to 13 metres (43 feet), but current studies of its fossil skull and other parts and comparisons with other pliosaurs, recommend that the true length was probably only 9–10 metres (30–33 feet).
Kronosaurus may have laid eggs in nests that they dug into the sand, much as modern-day ocean turtles do.
Other creatures preserved from the time include many fish and various molluscs such as squid, ammonites and belemnites. Some of their fossil shells bear tooth marks that could have been made by Kronosaurus, whose rear teeth were curved and suited to crushing hard shells.
Kronosaurus fossils have been established in Australia and Colombia, South America. It was discovered in Queensland, Australia, in 1889 by A. Crombie and was initially thought to be an ichthyosaur. It was named and described by Longman in 1924. It is named later than the Greek Titan Kronos, who ate his own kids, the Olympians.