Temporal range: Early Cretaceous
Kronosaurus 1000x665
Reconstruction of Kronosaurus by Gabriel Ugueto
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Sauropterygia
Order: Plesiosauria
Family: Pliosauridae
Subfamily: Brachaucheninae
Genus: Kronosaurus
Longman, 1924
Type species
Kronosaurus queenslandicus
Longman, 1924
  • Eiectus longmani (Noè & Gómez-Pérez, 2021)
  • Monquirasaurus boyacensis (Noè & Gómez-Pérez, 2021)

Kronosaurus (meaning "Lizard of Kronos") is a extinct genus of large carnivorous marine reptile that belong to the order of Plesiosauria and the suborder of Pliosauroidea.[1]

Kronosaurus lived during the early Cretaceous Period and was one of the largest genus of pliosaur, reaching about 9–10 meters in total body length. Kronosaurus was probably one of the top under-sea predators of its time.

As its holotype is highly fragmentary, its validity has come into question. This would result in a 2021 study reassigning it into a new genus: Eiectus. This move was highly criticized due to encouraging taxonomic instability, and several specimens have been proposed as neotypes. Because of this, many studies would use the name 'Kronosaurus' when referring to the genus.

Kronosaurus was likely an apex predator that would have fed on other marine reptiles. Fossilized remains of plesiosaurs and turtles have been found as stomach contents of some specimens.


In 1899, Andrew Crombie discovered six fossil conical teeth and gave to the Queensland Museum. Twenty-five years later, then-director Heber Longman formally described the specimen as the holotype of a new species: Kronosaurus queenslandicus. More Kronosaurus material, including a partial skull, was discovered in 1929, in the same location as Crombie's original find.


The genus was named after the most powerful Titan in Greek Mythology, Kronos.

The fossils of smaller plesiosaurs strongly suggests that Kronosaurus and its relatives may have preyed upon smaller plesiosaur species. This massive marine reptile was the biggest and baddest marine predator of the large inland sea that covered western Queensland in the Cretaceous. It used teeth the size of bananas to feast on ichthyosaurs, other plesiosaurs, turtles and fish. Kronosaurus has special air chambers on its snout that are used to scent prey in the same way as a pair of ears work, pinpointing exactly where a smell is coming from.

Body-length estimates had previously put the total length of Kronosaurus at 13.0 meters (43 feet). However, a more recent study comparing fossil specimens of Kronosaurus to other pliosaurs suggests that the previous estimate was, likely, an exaggeration, with the more accurate length estimations probably being only 9 to 11.5 meters (30–33 feet). The teeth of Kronosaurus are large in length (exceeding 7 centimeters - the largest up to 30 centimeters long with 12 centimeters crowns). However, they lack carinae (cutting edges) and the distinct trihedral (three facets) of Pliosaurus and Liopleurodon teeth. The combination of large size, conical shape and lack of cutting edges allows for easy identification of Kronosaurus teeth in Cretaceous deposits from Australia.

Kronosaurus lived in the Early Cretaceous Period (Aptian-Albian). The holotype specimen of the species K. queenslandicus was described by Longman in 1924, and is currently in the Queensland Museum. Hampe described a second species, K. boyacensis, in 1992 from Colombia. A preserved K. boyacensis can be seen in Villa de Leiva Boyaca, Columbia..

In more recent analysis, it has been said that all the non-holotype specimens of Kronosaurus have been put into different species and that the holotype should be restricted as the only specimen. Due to the fragmentary nature of the holotype, the authors found it undiagnostic compared to other pliosaurs, making Kronosaurus a dubious genus.[2]

This move was highly criticized due to it encouraging taxonomic instability. As a consequence, many studies thereafter would refer to the genus as Kronosaurus.


Kronosaurus belonged to the Pliosauridae family. The cladogram below follows a 2011 analysis by paleontologists Hilary F. Ketchum and Roger B. J. Benson, reduced to genera only.

"Plesiosaurus" macrocephalus
"Pliosaurus" andrewsi
OUMNH J.02247 (now Eardasaurus)


Fossil stomach contents from Northern Queensland show that Kronosaurus preyed on turtles and plesiosaurs. Fossil remains of large octobrachians [34] have been found in the same area as Kronosaurus. While no direct evidence of the animal predating on these octobrachians exists they fall within the projected size range of prey Kronosaurus would potentially have pursued.[7]

Large, round bite-marks have been found on the skull of an Albian-age Australian elasmosaurid (Eromangasaurus) that could be from a Kronosaurus attack.[35][36]


Kronosaurus is known from remains in Australia. The area was covered by a shallow inland sea called the Eromanga Sea which Kronosaurus inhabited.[37] This environment was notably cold, experiencing near freezing temperatures [38] and seasonal ice in certain regions.[7][39]

In popular culture[]