In Depth
Ceratodus was one of the most wide ranging fish to ever live on the planet, both geographically and temporally. This distribution was possible because back in the Triassic the major land masses of the continents were still close together which allowed several types of animals, most famously the dinosaurs, to spread out across the globe. Today however the group that Ceratodus belongs to is greatly diminished in numbers, but the closest living relative of Ceratodus is thought to be Neoceratodus forsteri, also known as the Queensland lungfish, Australian lungfush, Burnett Salmon and the Barramunda.
Being a lungfish Ceratodus would have had the ability to breathe air when out of the water, although it would have to ultimately return to the water to avoid drying out. As you have no doubt already realised by the fact that it was a lungfish, Ceratodus would have had a set of lungs that allowed it to absorb oxygen from the air. This is thought to have been the adaptation that several hundred millions of years earlier allowed the first tetrapods to leave the water for extended periods so that they could colonise the land. This also makes Ceratodus an archaic form that continued to survive because the adaptation made it so that the lungfish were best suited to their ecological niche.
Ceratodus would have had a long body, narrow in shape, with a severely reduced caudal tail that probably tapered off to a square, and did not extended beyond the fleshy tail. This shows that Ceratodus was not a particularly strong or fast swimmer, but as a bottom dwelling inhabitant of freshwater courses it only ever really had to contend with a downstream current at most. Additionally the feeding behaviour of Ceratodus probably would not have called for fast pursuit of prey.
Observation of lungfish today has shown that lungfish will eat both plants and animals, but the exact preference depends upon the size of the individual in question. Small juveniles have been seen eating both algae and small invertebrates like worms, the latter being an important source of protein that would aid fast growth. Larger and older individuals tend to incorporate bigger animals that can include other fish and also frogs into their diet. It’s perfectly reasonable to expect the same feeding behaviour in Ceratodus, in fact the ‘horned teeth’ which give Ceratodus its name seem to be more suited to a predatory lifestyle that suggests adult Ceratodus may have been more likely to have been exclusively carnivorous. This also suggests that lungfish like Ceratodus were filling the ecological niche left vacant by the disappearance of the xenacanthid sharks like Xenacanthus and Triodus.
Further Reading
– On fossil remains of Reptilia and fishes from Illinois. – E. D. Cope – 1875. – A new Ceratodus species from the Maleri beds, Andhra Pradesh. – S. C. Shah and P. P. Satsangi – 1970. – Upper Jurassic and Cretaceous lungfish tooth plates from the Western Interior, the last dipnoan faunas of North America. – J. I. Kirkland – 1987. – A new species of the lungfish Ceratodus (Dipnoi) from the Early Cretaceous of the eastern U.S.A. – Journal of Vertebrate Paleontology. – J. A. Frederickson, T. R. Lipka & R. L. Cifelli – 2016. – Ceratodus tunuensis, sp. nov., a new lungfish (Sarcopterygii, Dipnoi) from the Upper Triassic of central East Greenland. – Journal of Vertebrate PaleontologyJournal of Vertebrate Paleontology. – F. L. Agnolin, O. Mateus, J. Mil�n, M. Marzola, O. Wings, J. S. Adolfssen & L. B. Clemmensen – 2018.
