New insights into ancient environments using dental characters in Australian Cenozoic lungfish

Environmentally-related wear conditions and pathologies affecting the dentition of fossil lungfish from freshwater deposits in Australia have been analysed and compared with similar changes in the dentition of the living Australian lungfish, Neoceratodus forsteri. Fossil populations from the Namba, Etadunna, Wipajiri and Katipiri formations in central Australia, and the Carl Creek Limestone and the Camfield beds in northern Australia were assessed. Tooth plates from populations of living lungfish from the Brisbane River and Enoggera Reservoir in southeast Queensland were analysed for comparison. Tooth plates were measured to determine the numbers of different age groups in each population. They were assessed for abrasion, attrition, spur and step wear, erosion and caries, and for trauma and pathological conditions such as malocclusion, hyperplasia, abscesses, osteopenia and parasitic damage. All of these conditions are related to the environment where the fish lived, are found in living members of the group, and can be compared directly with those of fossil relatives. The results suggest that some of the fossil populations were at risk before climatic changes late in the Cainozoic destroyed their habitats. Some fossil lungfish populations, such as those of the Wipajiri Formation, exhibit active spawning and recruitment, good growth rates and a low incidence of disease and environmentally related damage to the tooth plates. Others, like those of the Katipiri and Namba Formations, include no young, and the adult fish were ageing and show environmentally-related damage to the dentition. Etadunna lungfish had active recruitment, but the tooth plates show a high incidence of attrition and caries. Riversleigh lungfish were actively spawning but did not grow large. Tooth plates from this latter deposit have a high incidence of pathological conditions. Fish from the Camfield Beds, where food was severely limiting, had little serious pathology but high levels of caries. Pathologies among living lungfish are common, but fossil fish were comparatively healthy, with few serious dental problems. Information from studies of fossil lungfish confirms that conservation of the few living species of lungfish depends on the maintenance of clean environments that provide adequate supplies of food and suitable sites for spawning and for the growth of young fish.