Australia: The Land Where Time Began

A biography of the Australian continent 

Refined Feeding Mechanisms

Feeding of a tooth-plated dipnoan can be observed in the Queensland lungfish. After crushing the food it is extruded as a long pulpy tube. This process is repeated until the food has been reduced to a mass of soft tissue then swallowed. This feeding method most probably was already being used by true tooth-plated dipnoans in the Devonian when the true tooth-plated dipnoans first evolved.

The Chirodipterid family have dental-plates, not true tooth-plates, and have no true teeth, and no cusps on most of the tooth plate. True tooth-plates have individual cusps, added to the margins of the plate as it grows. There are 3 Australian species of the Late Devonian Chirodipterid family from the Gogo Formation.

Chirodipterus, found originally in Europe and North America is a common genus in the Gogo Formation. Chirodipterus australis had broad crushing dental plates with tooth ridges.

Gogodipterus paddyensis had strongly developed tooth-ridges separated by deep grooves on each dental plate.

Pillararhynchus longi had long narrow tooth-plates with concave crushing surfaces, and the skull is deeper than the other species. The palate bone (parasphenoid) has a patch of dentine on its front surface, so it was probably used in food crushing.

Palaedaphus insignis was the largest of the Chirodipterids from the Late Devonian marine deposits in Belgium. It could have been about 2 m long, because its tooth-plates are about 14 x 10 cm.

Tooth-plates are characteristic of most known lungfish. The most primitive grade, those having 2 dorsal fins and shiny cosmine on the dermal bones, are represented by the dipterids of the Devonian. 

Sources & Further reading

John A Long The Rise of Fishes - 500 Million years of Evolution, University of New South Wales Press, 1995

Dipnoi