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Fossilized Hot Cross Bun Discovered

The recent discovery of a 110 million year old fossilized opal jaw bone fragment from Lightning Ridge could be of the most important fossil discoveries this decade, shedding new light onto the ancient world of the platypus.

The discovery by Andrew Cody of Cody Opals, provides an immense increase in the overall knowledge about the mysterious mammals of Australia's age of dinosaurs.

The right maxilla, lent to the Australian Museum by Mr Cody, dates back to the Mesozoic Period. It is unlike anything else found, as the molars in the lower jaw resemble a hot cross bun. Called Kollikodon ritchiei, because of its molar number and extraordinarily odd teeth, it comes from a new family of monotremes or Kollikodontidae (platypuses, echidnas, and their relations - all egg-laying mammals).

This new specimen, although found 30km from where an original lower jaw fragment was unearthed, almost perfectly matches, when placed in 'occlusion', the lower teeth donated to the Museum by Bob & Elizabeth Jones, experts in fossilised opals. This uncanny coincidence will greatly assist Museum researchers to understand precisely how 'Hotcrossbunidon' used its teeth to process its food.

Professor Michael Archer, Director of the Australian Museum commented: "The molars in the new specimen are bizarre - there is no other way to describe them. They look like crescent moons covered in hot cross buns. But the oddest aspect of these newly discovered teeth is that they are covered in 'pits' that appear to have been a feature of the molars when they were first erupted. These would provide extra cutting 'blades' to more efficiently process food."

"The same sort of pits often develop in other kinds of mammals, including humans, and when they do they also increase the 'functionality' of the teeth in which they develop. But in these more conventional mammals, they develop by wear later in life. Hence the teeth of conventional mammals increase in efficiency as they are worn - a curious phenomenon in itself. But in Hotcrossbunidon, this maximum efficiency was there from birth - and diminished as the animal used its teeth - because the pits would have been worn away."

He concluded: "These upper teeth are the most bizarre ever found in any mammal previously discovered. It is possible that this animal was using its teeth in a way that no other mammal has ever done, and that its teeth were more efficient from birth in terms of the ability to finely cut up its food - whatever that was!"

Museum scientists believe that this jaw could belong to a very distant and more specialised cousin of the Platypus. Indications are that at least two different kinds of egg-laying mammals were present at Lightning Ridge, living side by side during this period.

Because Australia was connected to Antarctica and that to South America at this time, we can presume that many of these bizarre creatures were also in those lands. But as yet, the only confirmation of this has been discovery of platypuses in Argentina in deposits that are 63 million years old - after the extinction of the dinosaurs.

Professor Archer will be working with Anne Musser, a PhD student from UNSW, to fully describe and formally publish the new discovery when the research into the specimen is complete.

Platypus fact sheet
Platypus fact sheet - PDF file