The fossilised tooth from the marine apex predator Kronosaurus is 110 million years old and was found in the rich opal fields of Outback South Australia in the 1980s.
The tooth – the only known one of its kind – was last year donated to the South Australian Museum by miners John and Sophie Provatidis of Majestic Opals who found it near the Outback opal town of Coober Pedy.
The state of South Australia produces 80 percent of the world’s opals, predominantly mined in Cooper Pedy, Andamooka, Mintabie, and Lambina.
The opalised Kronosaurus tooth will go on permanent public display from tomorrow at the Museum of South Australia in Adelaide, which has a world-renowned opal collection.
Sophia Provatidis said she and her husband saw some “tooth-like” aspects to the opalised fossil but were unsure of its origin.
“We didn’t really know what it was,” she said.
The couple added the tooth to their personal fossil collection before displaying it at an industry showcase.
The Museum of South Australia became aware of the item around this time.
Senior Collection Manager of the Earth Sciences at the South Australian Museum Ben McHenry said he had always “lusted after” the tooth.
The specimen itself is 7cm long. McHenry said the whole tooth could have been 10-15cm in length, but even the tip was “scientifically priceless”.
“It’s such a rarity. It’s the only known opalised tooth of the Kronosaurus,” he said.
“There isn’t actually much material of Kronosaurus known.
“The average length of an adult Kronosaurus was 10 meters long with a skull of two meters long.”
Known as the T.rex of the ocean, Kronosaurus swam beneath the waves during the Early Cretaceous period when the Eromanga Sea covered central Australia. The sediments from this seabed now form the rocks of the Great Artesian Basin.
McHenry said the forming of opals in South Australia began with the Eromanga Sea being drained through the Gulf of Carpentaria in northern Australia – and the eventual weathering.
Groundwater passed through the sediments and dissolved the sulphurous materials, forming sulphuric acid.
“This sulphuric acid has actually percolated through the sediments and on its way dissolved out a lot of silica,” said McHenry.
“But it has also dissolved away fossils and left a cavity.
“That silica, which has actually been dissolved from the sediments and redeposited in cracks and cavities, which becomes the opal.
McHenry said the opal replaced the contents of this Kronosaurus tooth some time in the last 40 million years.
“It was just sitting underground, waiting for someone to find it,” he said.
“Where these opals are found now are out in the middle of the desert and some places look like the surface of the moon. It’s hard to image 100 million years ago we were at the bottom of the ocean.
“This tooth is reflective of our opal industry – 80 per cent of all our opals come from South Australia – but it also tells the story of South Australia from 110 million years ago.”
The opalised Kronosaurus tooth will go on permanent public display from tomorrow, Friday, March 29, at the Museum of South Australia in Adelaide as part of its Opal Fossil gallery.Jump to next article