Koolasuchus
Encyclopedia
Koolasuchus is an extinct genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of brachyopoid
Brachyopoidea
Brachyopoidea is a superfamily of temnospondyls that lived during the Mesozoic. It contains the families Brachyopidae and Chigutisauridae. The earliest records of brachyopids are from the Lower Triassic in Australia...

 temnospondyl in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Chigutisauridae
Chigutisauridae
Chigutisauridae is an extinct family of large temnospondyl amphibians. The only genera recognized as belonging to Chigutisauridae at the current time are all from Gondwana and include Koolasuchus and Siderops.-References:*Sengupta, D.P. 1995. Palaeontology 38: 19-59.*Sengupta, D.P. 2003...

. Fossils have been found from Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 and date back 120 Ma to the Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...

 stage of the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

. Koolasuchus is the latest known temnospondyl. Koolasuchus is known from several fragments of the skull and other bones such as vertebrae, ribs, and pectoral elements. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 K. cleelandi was named in 1997.

Description

Koolasuchus was an aquatic temnospondyl estimated to have been around 4 to 5 m (13.1 to 16.4 ft) in length. Its mass has been estimated to be up to 500 kilograms (1,102.3 lb). Although represented by incomplete material, the skull was likely 65 centimetres (25.6 in) long. Like other chigutisaurids, it had a wide, rounded head and tabular horns projecting from the backside of the skull.

History

Koolasuchus was named in 1997 from the Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...

 Strzelecki Group of the Wonthaggi Formation
Wonthaggi Formation
The Wonthaggi Formation is a geological formation in Victoria, Australia whose strata date back to the Early Cretaceous. It is part of the Strzelecki Group. Dinosaur remains are among the fossils that have been recovered from the formation....

 in Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....

. 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
San Remo, Victoria
San Remo is a town in southern Victoria, Australia in the Gippsland region. Formed as a fishing village, its economy is now more largely based around tourism. It is also notable as the town on the mainland end of the bridge to Phillip Island...

. 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
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...

 Mike Cleeland.

Paleobiology

Koolasuchus inhabited rift valleys in southern Australia during the Early Cretaceous. During this time the area was below the Antarctic Circle
Antarctic Circle
The Antarctic Circle is one of the five major circles of latitude that mark maps of the Earth. For 2011, it is the parallel of latitude that runs south of the Equator.-Description:...

, and temperatures were relatively cool for the Mesozoic. Based on the coarse-grained rocks in which remains were found, Koolasuchus likely lived in fast-moving streams. As a large aquatic predator, it had a similar lifestyle to crocodilians. Although crocodilians were common during the Early Cretaceous, they were absent from southern Australia 120 million years ago, possibly because of the cold climate. By 110 Ma, represented by rocks in the Dinosaur Cove
Dinosaur Cove
Not to be confused with the children's book series of the same name.Dinosaur Cove in Victoria, Australia is a fossil bearing site in south-east of the continent where the Otway Ranges meet the sea to the west of Cape Otway, adjacent to Great Otway National Park .The inaccessible ocean-front cliffs...

 fossil locality, temperatures had warmed and crocodilians had returned to the area. These crocodilians likely displaced Koolasuchus, leading to its disappearance in younger rocks.

In popular culture

Koolasuchus was featured in Episode 5 of Walking with Dinosaurs
Walking with Dinosaurs
Walking with Dinosaurs is a six-part documentary television miniseries that was produced by BBC, narrated by Kenneth Branagh, and first aired in the United Kingdom, in 1999. The series was subsequently aired in North America on the Discovery Channel in 2000, with Branagh's voice replaced with that...

. The episode depicted Koolasuchus as an ambush predator, like a crocodile.
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