In 2010, an old swivel gun was found on a remote Northern Territory beach and experts say it might have been lying there for 250 years.

While that creates all sorts of intrigue about when Australia was discovered — Captain Cook laid claim to it in 1770 — it also points to this nation’s deep past.

When most people think about archaeology and palaeontology, images of a whip-cracking Indiana Jones usually spring to mind closely followed by images of ancient pyramids and forgotten tombs in places both distant and mysterious.

But the swivel cannon got us thinking. What other amazing finds have been unearthed in our wide, brown backyard?

Lost shipwrecks, mass-graves, 1000-year-old coins, bizarre animals — think A Country Practice‘s Fatso the Wombat, but about 100 times bigger! — and ancient civilisations are just some of the secrets revealed. And they’re only the ones we know about.

Here some of the most fascinating, historically-important discoveries in Australia.

1000-year old Arab coins found in Northern Territory

Macassan trepangers weren’t the only seafaring society to beat Captain Cook to Australian shores. Five 1000-year-old coins, minted in the island sultanate of Kilwa Kisiwani off the coast of modern-day Tanzania, were unearthed in the Wessel Islands by RAAF radio operator Morry Isenberg in 1944. Their discovery could indicate that Australia had been found by seafarers hundreds of years prior to Cook’s arrival.

While an expedition to the Wessel Islands last year, funded by Australian Geographic and spearheaded by anthropologist Dr Ian McIntosh (below), failed to unearth any more coins, they did find interesting samples of washed up shipping timbers and metalwork, along with Aboriginal rock art depicting men and sailing ships.

Dr Ian McIntosh points to the Wessel Islands where he lead an unsuccessful expedition to find more coins. Photo: AAP

Cave painting of ancient bird in Arnhem Land

Rediscovered in 2008, an ochre cave painting at the centre of the Arnhem Land plateau generated lots of attention due to its detailed depiction of the megafauna species Genyornis. This huge bird, over two metres in height and weighing a hefty 230kg, roamed Australia during the Late Pleistocene era over 40,000 years ago.

The existence of this rock painting means one of two things. Either Genyornis was roaming Australia much later than scientists have been able to establish, or the painting of the thunderbird could be 40,000 years old. As a comparison, the Pyramid of Giza is just under 5000 years old, and the oldest cave painting found in Europe is 40,800 years old.

Either way, indigenous groups were living alongside (and probably eating) these creatures long before Macassan trepangers knew what a boat was.

Aboriginal rock painting found in Arnhem Land. Photo: AAP

Mega-wombat graveyard

A wombat the size of a rhinoceros with a pouch big enough to carry an adult human sounds like an animal not to be trifled with. But Diprotodon — the largest marsupial that ever lived — was the victim of more than one type of predator during the Pleistocene era, a period ranging from 2.5 million to 12,000 years ago.

The discovery of a diprotodon mass grave in remote Queensland, containing the fossilized remains of up to 50 of the creatures, has helped shed light on the behavioural habits of these huge creatures. The gravesite also contained teeth from 6 metre lizard Megalania and prehistoric crocodiles, suggesting that the diprotodons, trapped by boggy ground, became an easy meal for the large predators. Yum.

A reconstructed model of a diprotodon, a rhino-sized mega-wombat. Photo: AAP

Titanosaur: Australia’s biggest dinosaur

Towering up to 18 metres and weighing over 100 tons, roughly the weight of a Boeing-757, titanosaurs were some of the heaviest creatures to ever roam the Earth.  While these huge creatures roamed the Earth 98 million years ago, there was no evidence of them in Australia until 2005-2006, when scientists unearthed two sets of titanosaur fossils in southwest Queensland.

One of the creatures, nicknamed ‘Cooper’ after Cooper Creek where it was discovered, is not only one of largest dinosaurs found in Australia, but also represents a new species, one that hasn’t been found anywhere else in the world.

Stuart and Robin McKenzie pose with a titanosaur bone found on their property at Eromanga, Queensland. Photo: AAP

Shark Bay stromatolites

Discovered in 1956, the stromatolites at Shark Bay in Western Australia are some of the oldest living creatures still in existence today and represent one of the first signs of life on our planet.

Stromatolites are a solid structure created by single-celled microbes called cyanobacteria, which form colonies and trap sediment with their sticky surface coating.

The trapped sediment reacts to calcium carbonate in the water to form limestone, similar to a coral reef. These structures, which have been described as resembling fossilised cow-pats, build up very slowly – it can take a stromatolite 100 years to grow 5 centimetres.

Shark Bay is one of the few places in the world where visitors can see living creatures that existed before the dinosaurs, over 2.8 billion years ago.

A graphic of proterozoic ocean floor with bun-shaped stromatolites. Photo: AAP

Indonesian Swivel Cannon that predates Captain Cook

Captain Cook receives a lot of credit from historians for “discovering” Australia in 1770. But while we know the indigenous population was here long before Cook landed on our shores, the discovery of a bronze 107 centimetre-long swivel gun on a Northern Territory beach in 2010 suggests foreign contact with Australia before Captain Cook.

Discovered by Darwin boy Christopher Doukas during an unusually low tide on Dundee Beach, the light artillery piece is believed to have belonged to Indonesian sailors known as Macassan trepangers. These sailors harvested sea cucumbers from the ocean floor, which they sold to Chinese merchants who valued the creatures as a rare delicacy and a “potent aphrodisiac.”

Researchers Michael Hermes, Tim Stone and Ian McIntosh with the swivel gun. Photo: AAP

Australia’s Lost World

Google has become synonymous with helping find things on the Internet. Information, people, locations; Google can find them all. However, it’s rare that the search engine can help find one new species, let alone three. But with a bit of assistance from Google Earth, Dr Conrad Hoskin from James Cook University did just that, finding Australia’s very own Jurassic Park, a “lost world” of new species.

Located at Cape Melville in northern Queensland, this small patch of rainforest sits upon a gigantic pile of boulders, which serve to separate and protect its inhabitants from the outside world. An expedition to the plateau last year, funded by the National Geographic Society, discovered the three new species during their time there, and while the Cape Melville Leaf-tailed Gecko or Blotched Boulder-frog may not be as big as a diprotodon or titanosaur, they have both lived in Australia since the time of the dinosaurs.

Leaftail gecko in the rugged Cape Melville mountain range, northeastern Australia’s Cape York Peninsula. Photo: AAP