Old Fossil Fruit Changes Evolution Story

ABC Capricornia

Topic:Fossils

Research into preserved fossil fruits has led to the discovery of a new genus and species. (Supplied: Queensland Museum)

In short:

The first fossil record of the Melastomataceae plant family in Australia or eastern Gondwana has been identified in specimens from central Queensland.

A paper on the fossils published this month challenges what scientists previously believed about the plant's origins.

It also led to the discovery of a new genus and species.

When scientists were first handed exceptionally preserved fossils from rural central Queensland, they were stumped.

"It was an unusual discovery because when we first found it, it looked a bit like lizard skin," Queensland Museum's principal geoscience scientist, Andrew Rozefelds, said.

"I just went, 'It can't be', because when you get plants, you don't tend to get vertebrates as well.

"We were faced with a plant we've never seen before."

The plants were later identified as the first fossil record of the Melastomataceae family in Australia or eastern Gondwana, an ancient supercontinent.

It also led to the discovery of a new genus and species, Capella raulingsii, which was previously unknown to science.

Melastomataceae are now found around the tropics, with several species in Australia, mostly in the tropical north and east.

Andrew Rozefelds with a fossilised Capella raulingsii. (Supplied: Queensland Museum)

Earlier this month, Dr Rozefelds and his colleagues published a paper in the International Journal of Plant Sciences, which also challenged beliefs about how the plants came to be in Australia.

"The most recent molecular data suggested that this family of plants migrated into Australia from South-East Asia," he said.

"The fossil evidence we've got would suggest this isn't the case."

The internal anatomy of the Capella raulingsii. (Supplied: Queensland Museum)

Dr Rozefelds, who is also an adjunct research fellow at CQ University, said the research found the plants were already in Australia about 30 million years ago, which suggested they were of Gondwanan origins.

"These fossils show that members of the Melastomataceae were growing in Australia tens of millions of years before the continent made contact with South-East Asia," Dr Rozefelds said.

Gondwana began breaking up about 180 million years ago.

It split into continents including Australia, South America, Africa, Arabia, Madagascar, India and Antarctica.

From volcanic rainforests to farming land

The University of Queensland's Anita Milroy, who was among the paper's co-authors, said the fossils were found in silcretes, an extremely hard rock, near Capella on brigalow, farming country.

Anita Milroy has spent time at Capella near the fossils, and says the area is an important site for fossil preservation. (Supplied: Anita Milroy)

"Around 30 million years ago, it would have been a rainforest … and there are some living relatives [of the plants] now in the Daintree [near Cairns]," Dr Milroy said.

Dr Milroy said she contributed to the research by using synchrotron imaging, a type of high-intensity X-ray, on the specimens.

"Now it's a technique that's used right across the board in palaeobotany," she said.

"We can actually see inside these fruits, we don't have to destroy them."

An illustration of the fruit and what the plants' leaves may have looked like. (Supplied: Queensland Museum)

The scientists' research also describes the first whole fruit of the Melastomataceae family found anywhere in the world.

Usually, fossil fruits are flattened or incomplete, but Dr Milroy said the Capella area was "internationally significant" because the region historically had volcanoes, and eruptions helped preserve the fossils.

University of Melbourne palaeontologist Vera Korasidis, who was not involved in the study, agreed, saying further studies should be undertaken in the area.

"Unlike in bones or teeth that we associate with dinosaurs, which are naturally quite hard, soft tissues that we associate with plants tend to rapidly deform or decay before fossilisation occurs."

Dr Korasidis described it as an "exceptional" find.

"It's quite exciting to be able to rewrite the narrative and say that perhaps they evolved or were present in north-east Queensland, and then spread northward, as opposed to the other way around."

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