Long in the tooth, but still a precious gem

29 March 2019

Known as the T.rex of the ocean, the only identified opalised tooth of the enormous marine reptile Kronosaurus (pliosaur), will go on display at the South Australian Museum today. 

The Kronosaurus swam beneath the waves during the Early Cretaceous period when South Australia was covered by the Eromanga Sea and dinosaurs roamed the land. The sediments laid down on this ancient seabed now form the rocks of the Great Artesian Basin.

In the 1980s Sophia and John Provatidis of Majestic Opals found a specimen at Coober Pedy that had ‘tooth like’ similarities but were unsure of its origin.   
“Mineral experts at the Museum and Adelaide opal specialist Nick Kollias assisted us in properly identifying it as part of a fossilised tooth from Kronosaurus which had opalised,” Sophia and John said. 

Growing up to 10 meters in size, these huge marine carnivores had sharp, conical teeth - used to break hard shells and eat prey – its jaw alone measuring two metres. 
Ben McHenry Senior Collection Manager, Earth Sciences at the South Australian Museum says this is a fantastic addition to the Museum’s internationally recognised opal collection. 

“South Australia is famed internationally as the opal capital of the world and has produced over 80% of the world’s precious opals from the gem fields in the state’s far north,” Mr McHenry said. 

“Opal formation began in South Australia when sediments were laid down in the ancient Eromanga Sea over 100 million years ago. This inland sea acted as a breeding ground for marine reptiles such as plesiosaurs and ichthyosaurs. As they died, their bodies sank to the seafloor and were incorporated into the sediments. Tens of millions of years passed and the bones of these animals were replaced with opal as groundwater percolated through the rocks,” he said.
The tooth has been donated to the Museum under the Federal Government’s Cultural Gifts Program. This program generously supports collecting institutions like the South Australian Museum with tax concessions. 

“Sophia and John Provatidis have been great supporters of the Museum over the past 20 years, making several donations and also making a significant contribution to the Treasures Room of the Museum’s Opals Exhibition in 2015. We’re very grateful for their continued support,” Mr McHenry said.  

The opalised Kronosaurus tooth will be on display in the Opal Fossil gallery at the South Australian Museum.