Scientific discovery shows ‘drop crocs’ once existed in Australia
Palaeontologists have uncovered a type of crocodile that would have hunted among the trees, all by looking at their fossilised eggshells.
We’re well-known in Australia for our ‘drop bear’ myth, a scary story used to frighten gullible tourists on their first trips down under.
It turns out the myth might not be so unrealistic, with scientists recently finding evidence of a five-metre-long ‘drop crocodile’ that lived 55 million years ago.
A group of palaeontologists have unearthed Australia’s oldest crocodile eggshells at a dig site in inland Queensland, finding they belong to mekosuchines, an ancient crocodile that’s now long-extinct.
“It’s a bizarre idea,” palaeontology professor Michael Archer admitted.
“But some of them appear to have been terrestrial hunters in the forest.
“They were perhaps hunting like leopards — dropping out of trees on any unsuspecting thing they fancied for dinner”.
What are mekosuchines?
While freshwater and saltwater crocodiles only arrived in Australia around 3.8 million years ago, mekosuchines would have dominated inland waters 55 million years ago.
They grew up to five metres long, and some were “at least partly semi-arboreal (tree-dwelling),” Professor Archer said.
The paper explains how mekosuchines filled strange ecological niches.
“These eggshells have given us a glimpse of the intimate life history of mekosuchines,” said the lead author of the study, Xavier Panadès i Blas.
“We can now investigate not only the strange anatomy of these crocs, but also how they reproduced and adapted to changing environments.”
While this information will be historically significant, it might also help us understand how species can adapt to ongoing changes in the environment.
Where were the fossils found?
The fossils were discovered in the town of Murgon, Queensland.
Scientists have been digging there for decades in a clay pit that was once a lake, and now a place of rich discovery.
Here, excavation has found evidence of Australia’s oldest-known mammals from the Tertiary period (55 million years ago).
Soft-shelled turtles and Australia’s oldest-known frogs lived in the area, as well as Australonycteris clarkae, Australia’s oldest bat.
The world’s earliest-known songbirds were also known to have lived there, making researchers think they might have evolved in Australia.
What can eggshells tell us?
Apparently, quite a lot.
After being examined under optical and electron microscopes, the shell fragments suggested that the mekosuchine crocodiles would have laid eggs on the margins of the lake.
This pointed to adaptivity in their reproductive strategy amid fluctuating conditions.
“They preserve microstructural and geochemical signals that tell us not only what kinds of animals laid them, but also where they nested and how they bred,” Blas said of the eggshell discovery.
“Our study shows just how powerful these fragments can be.
“Eggshells should be a routine, standard component of palaeontological research — collected, curated and analysed alongside bones and teeth.”
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Originally published as Scientific discovery shows ‘drop crocs’ once existed in Australia
