Birds do it, bees do it, even ancient long-legged flies did it…
At least this pair did — until they were suffocated in a glob of tree resin around 40 million years ago.
These flies are locked in amorous embrace, looking just the way they did when they died.
They are part of giant haul of the oldest fossilised resin, or amber, to be found in the Southern Hemisphere, according to researchers whose findings are published today in the journal Scientific Reports.
The list of life-forms found ‘snap frozen’ in time in this fossil treasure trove sounds like the Twelve Days of Christmas.
It includes two mating flies, amazing ants, slender springtails, a cluster of juvenile spiders, a bunch of biting midges, and new liverwort and moss species.
“This is one of the biggest discoveries in Australian palaeontology,” said lead author Dr Jeffrey Stilwell of Monash University.
The haul of 5,800 amber pieces from sites across southeastern Australia, Tasmania and New Zealand goes some way towards balancing the planet’s amber fossil record.
“Almost all amber records are from the Northern Hemisphere. There are very few from the Southern Hemisphere,” Dr Stilwell said.
He said the oldest amber was 230 million years old, from the Fingal valley in northwest Tasmania, which matches the age of amber found in the Northern Hemisphere.
The researchers found the two mating flies (Dolichopodidae) in 40 – 42 million year-old amber from a coal mining site in Victoria.
The fossils come from a time when Australia was part of a slowly disintegrating supercontinent called Gondwana, which included Antarctica and other land masses.
The climate was warm and moist and the land was covered in forest full of bugs.
At the same coal mining site the researchers found the first Australian amber fossils of slender springtails and ants.
“I am surprised that in more than 100 years of studying fossils in Australia that a fossil ant has never been found,” Dr Stilwell said.
“So we’re getting a real glimpse into some of these ancient terrestrial ecosystems that nobody’s ever known anything about.”
Further south in a site in Western Tasmania the researchers found 54 – 52 million-year-old amber fossils, including a complete mite and a scaly insect called a “felt scale”.
“These are the oldest animals and plants in amber from the entire southern Gondwana supercontinent,” Dr Stilwell said.
He said the team recovered a lot of material from the Alcoa coal mine in Anglesea Victoria.
“We were able to bulldoze the site and we now have a freight container full of amber-bearing coal to go through,” he said.
While their lab is currently in shutdown because of the coronavirus pandemic, the team is looking forward to getting on with the work.
“We’re just getting started, there’s so much to learn.”
A window on the past
The findings have been welcomed by other experts.
“[They] do a great job in revealing that Australasia has a range of old to very old amber deposits and that, significantly, there is good potential to find fossil invertebrates and plants in them,” said Trevor Worthy, a palaeontologist at Flinders University.
Ken Walker, a senior curator in entomology from the Museum of Victoria said the findings were a significant window to the past.
“Not just as fossils but as 3D animals in a state of suspended animation. Imagine having a pair of mating flies from millions of years ago,” Dr Walker said.
“What these specimens clearly show is that most of the major groups of insects had already diversified by the Gondwana times. I find it extraordinary that the amber ant specimens have direct link to ant groups alive today.”
“What an exciting discovery,” added palaeobiologist Dr David Martill from the University of Portsmouth.
Not only is amber very rare in Australia, he said, but some of the pieces were very large.
“This means there is potential for larger inclusions. Who knows, maybe you will find lizards and birds like in the Burmese amber.”
Dating the fossils
Amber is difficult to date directly but Dr Stilwell and team dated the fossils by relying on the age of the rock surrounding them.
“All of our amber is in situ, it’s found in the rock which we can date,’ he said.
By contrast, it’s not clear where a 2006 discovery of amber fossils found on beaches in northern Queensland’s Cape York have come from.
Like the new finds, this amber is filled with lots of insects and spiders.
Researchers believe Cape York amber is around 15 million years old, based on dating of plant material within the fossils.
But it is not yet known whether the amber there is being flushed out of swamps in the area, or washed in from elsewhere.