Fossils of the Winton Formation

A fossilised skull of Isisfordia duncani, a small crocodile from the Cretaceous Period of western Queensland. The snout is more elongated than that of modern crocodiles and the skull structure is also different, however, Isisfordia belonged to a group that was ancestral to all modern crocodiles.

Lungfish

Lungfish have existed since the Age of the Fishes during the Devonian Period, more than 400 million years ago, when these animals underwent a rapid radiation. As a group, lungfish are considered to be closely related to coelacanths (rare, lobe-finned fish dating to the Devonian), and to tetrapods, the group of vertebrates that gave rise to land-based animals.

Image: Toothplate of the lungfish, Metaceratodus wollastoni. Lungfish are a common element in the freshwater fauna of the Winton Formation.

There are three living genera of lungfish – Protopterus in Africa, Lepidosiren in South America, and Neoceratodus in Australia. Analysis of molecular data and fossil evidence suggests the South American and African groups split during the Cretaceous Period and this is consistent with the time that geologists believe these two land masses separated.

Early in their evolutionary history, lungfish evolved a successful body plan and life strategy. As a result, their basic body plan has remained relatively consistent, leading to their being described as 'living fossils'.

During their long history, lungfish have been well adapted to their environments. The main evidence of evolutionary change is in their fan-like tooth plates, which they use to crush food. Depending on the time period and species, lungfish tooth plates vary in appearance and can be used to distinguish different species.