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Image Fish fossil

TLF ID R6895

This is a colour photograph of an ancient fish ('Wadeichthys oxyops') fossilised in mudstone. This specimen is from the Koonwarra fossil bed in South Gippsland, Victoria. The fins, tail and body scales of the fish are clearly visible. Museum cataloguing numbers are written on the rock.

Educational details

Educational value
  • This fish fossil is from the Koonwarra fossil bed, which formed 118-115 million years ago during the Cretaceous Period. The Koonwarra fossil bed contains fossils as diverse as plants, fish, insects, crustaceans, spiders, worms, bird feathers, a horseshoe crab and a mussel.
  • Fossils are the remains, moulds or traces of dead plants or animals preserved in rock, mostly sedimentary rock such as sandstones, siltstones, shales and limestones. Fossils are an important source of information about the Earth's past. As well as shedding light on previous climatic and environmental conditions, they provide valuable clues about the evolution of plants and animals, the age and formation of rocks, and the former positions of the continents.
  • The Koonwarra fossil bed is composed of fine-grained mudstone and is believed to have formed in the shallow part of a large freshwater lake. The numerous fish fossils found here are well preserved and show no signs of rotting, which suggests the lake probably froze over in winter, trapping and killing many animals due to lack of oxygen. Insect fossils are also well preserved, supporting the theory that the freezing lake rapidly preserved the plants and animals.
  • The Koonwarra fossils provide invaluable information about the climate of the ancient environment. Some of the fossilised insects such as the mayflies and a beetle are similar to modern forms found only in cool alpine and subalpine regions, indicating that the climate at the time was cool. This is consistent with the geographic position of Australia at the time, which was much further south and attached to Antarctica, with southern Victoria in the polar regions.
  • The fish fossils of the Koonwarra fossil bed were small and therefore were probably juveniles or small adults inhabiting the shallow waters of the lake, as is common in modern fish. Several fish species have been identified in the Koonwarra bed, and a lungfish similar to those of today has been found at a nearby site in rocks of the same age.
  • This extinct fish species belongs to the ray-finned fish, also known as the actinopterygians. The ray-fins are the largest group of modern fish, containing about 30,000 living species. The ray-fins have a swim bladder, bones with an enamel layer, a single dorsal fin and paired pectoral (shoulder) and pelvic fins. During the Cretaceous Period when the Koonwarra fossil bed formed, ray-fins were the most abundant type of fish.
  • The prehistoric actinopterygians diversified into several groups hundreds of millions of years ago, including the neopterygians, represented by 'Wadeichthys oxyops'. The neopterygians (meaning new fin) developed evolutionary advances that included more mobile mouthparts, fewer vertebrae, a simplified fin structure and a more compact symmetrical tail.
Year level

3; 4; 5; 6; 7; 8; 9; 10; 11; 12

Learning area
  • Science

Other details

  • Author
  • Person: Frank Coffa
  • Description: Author
  • Contributor
  • Name: Museum Victoria
  • Organization: Museum Victoria
  • Description: Content provider
  • Address: VIC, AUSTRALIA
  • URL:
  • Name: Education Services Australia
  • Organization: Education Services Australia
  • Description: Data manager
  • Person: Frank Coffa
  • Description: Author
  • Copyright Holder
  • Name: Museum Victoria
  • Organization: Museum Victoria
  • Address: VIC, AUSTRALIA
  • Publisher
  • Name: Education Services Australia Ltd
  • Organization: Education Services Australia Ltd
  • Description: Publisher
  • Address: VIC, AUSTRALIA
  • URL:
  • Resource metadata contributed by
  • Name: Education Services Australia Ltd
  • Organisation: Education Services Australia Ltd
  • Address: AUSTRALIA
  • URL:
Access profile
  • Colour independence
  • Device independence
  • Hearing independence
Learning Resource Type
  • Image
  • © Education Services Australia Ltd and Museum Victoria, 2016, except where indicated under Acknowledgments