Lower Cretaceous Non-Marine Sharks & Bony Fish

Australia: The Land Where Time Began

Lower Cretaceous Non-Marine Sharks & Bony Fish

In Australia the remains of non-marine sharks from the Cretaceous are extremely rare, though opalised teeth of lamniform sharks and the jaw plate of a small ray have been found in the Griman Creek Formation, Lightning Ridge, though the shark teeth are unidentified they are comparable to marine forms. It has been suggested that they may be of forms that were moving from estuaries and lagoons upstream to freshwater.

Fossils of bony fish have been found in the Griman Creek Formation and the Koonwarra Fossil Beds. It has been suggested that seasonal winter kills were possibly the result of large numbers of fish suffocating when lakes froze over in winter, restocking being from rivers emptying into the lakes following the summer thaw. A primitive teleost, Leptolepis koonwarri and a palaeoniscoid, Coccolepis woodwardi have been found in the Koonwarra Fossil Fish Beds. There was also an archaeomaenid, Wadeichthys oxyops, a species known from the Jurassic in Australia, and a clupeioform, Koonwarria manifrons, and a ceratodont lungfish that is unidentified. Among the fish found in the Wallumbilla Formation at White Cliffs are ceratodonts such as Metaceratodus wollanstoni, a large-bodied fish that has also been recorded from the Wallumbilla Formation at White Cliffs, as well as possibly from the Bulldog Shale.

In the Wonthaggi Formation at Cape Patterson, southern Victoria, a ceratodont, Archaeoceratodus avus, has been found, and also in the Hawkesbury Sandstone; this has been described as an exceptionally long evolutionary history, extending throughout much of the Mesozoic.

In the Otway Group of southern Victoria the teleost Leptolepis crassicaudata, and other bony fish that are described as enigmatic, such as Psilichthys selwyni, have been recovered. In the Griman Creek Formation, Lightning Ridge, jaw fragments and vertebrae of teleost-like fish, and scales of Richmondichthys, a marine aspidorhynchid, and a small skull that is thought to be that of an early eel that was rather structurally advanced. At lightning Ridge the ceratodonts include Metaceratodus Wollastoni, an ubiquitous species that has been reported from the Mackunda Formation, the Winton Formation, and in central Australia, Queensland and South America, the lungfish of the present Neoceratodus fosteri, having survived virtually unchanged to the present from the Cretaceous. In the Eumeralla Formation at Dinosaur Cove, and Point Lewis on the Victorian coast, another species of lungfish has been found, Neoceratodus nargun. N. nargun, a species that survived from the Cretaceous to the Pliocene, has delicate tooth plates.