Australia: The Land Where Time Began

A biography of the Australian continent 

Dicynodont                                                                                                                                 

The 1980s discovery: Early Triassic    abt 225 million years

The 2003 discovery: Early Cretaceous abt 105 million years

These are therapsids, or mammal-like reptiles. In appearance they have been compared to pigs or hippos. They had a beak like a turtle and 2 tusks in their upper jaw, as is found in walruses. They flourished prior to the great extinction episode that occurred at the Permian-Triassic boundary. Prior to the extinction event they were the most diverse and abundant of the herbivorous land vertebrates up until the late Permian. A few survived the great extinction event when vast numbers of species died out, and began to radiate again, but this time they had competition from the rising dinosaurs, which eventually prevailed over the dicynodont fauna. 

The quadrate bone of dicynodonts is in the form of a double knuckle, the lower jaw articulated to it in a manner almost like a pulley.

Prior to their extinction near the end of the Triassic they had a world-wide distribution. They have been found in North America, Asia and various countries in Africa. Over all of their known range outside of Australia they declined and then died out completely by the end of the Triassic. Prior to the most recent discovery, the only previously known dicynodont fossils from Australia were in Early Triassic rocks at The Crater, south-west of Rolleston, Queensland. 

The most recent discovery by Dr Tony Thulborn of University of Queensland, and his wife Dr Sue Turner, Published in the 7 May 2003 issue of Proceedings of the Royal Society of London, which was actually collected in 1915, but not studied until 'It was refound in a drawer in the SB Queensland Museum when we were moving the collections to Hendra - the technician brought it to me and I realised that Longman had been right in his thoughts on the main specimen, i.e. it was like the dicynodont tusks from S Africa. My husband confirmed my id and we went on to work on the material (as we continue to do, seeking more; a subsequent field trip to the site in 2003 did not reveal more but we look in other museum drawers!). And of course in 1915 when it was sent down form western Queensland, the concept of continental drift had not reached Queensland - I doubt that HAL [Heber Albert Longman] had seen the German version of Wegener's book nor did he ever espouse the concept as far as I know later in life. This has been discussed by me in other historical papers/presentations on Longman and is part of the work I am doing on his relationship with the great dinosaur worker, von Huene.' (Dr Sue Turner, Source 3).

This most recent discovery in Queensland has been dated to 105 Ma, making it the latest known surviving dicynodont, and surviving to a time when dinosaurs were dominant in other parts of the world, surviving for 110 million years longer than previous finds indicated, according to Drs Thulborn and Turner (Source 5).

Sources & Further reading

2. Long, John A, 1998, Dinosaurs of Australia and New Zealand, University of New South Wales Press.
3. The last dicynodont: an Australian Cretaceous relict
4. Patricia Vickers-Rich, Thomas Hewitt Rich, 1993 Wildlife of Gondwana, Reed Australia.
5. One Giant mystery

Links

1. Australia in the Triassic
2. The Triassic Period - Dicynodonts

Reptiles