Scientists say they have unearthed Australia’s oldest known crocodile eggshells, a discovery that could shed light on ancient reptiles that may have hunted prey by dropping on them from trees.

The eggshells belonged to mekosuchine crocodiles, a prehistoric creature that dominated Australian waters 55 million years ago — a long time before the arrival of saltwater and freshwater crocs on the continent around 3.8 million years ago.

Paleontologist Michael Archer said mekosuchine crocodiles could grow to at least 5 meters (around 16 feet) long, and some hunted from trees. Australian researchers have dubbed them “drop crocs,” a reference to the feared “drop bear” — the vicious, carnivorous cousin of the country’s beloved koalas, or so the legend goes.

“It’s a bizarre idea. But some of them appear to have been terrestrial hunters in the forests,” said Archer, a professor at the University of New South Wales in Sydney who took part in the study.

“They were perhaps hunting like leopards — dropping out of trees on any unsuspecting thing they fancied for dinner,” he said in a statement.

A team of international scientists, led by Institut Català de Paleontologia Miquel Crusafont in Barcelona, dug up the fossils from a rancher’s backyard in southeast Queensland and studied them. They reported their findings Tuesday in the Journal of Vertebrate Paleontology.

The ancient crocodile eggshells are helping scientists to understand the anatomy of these reptiles, as well as their reproduction patterns and adaptability, the study’s lead author, Xavier Panadès i Blas, said.

“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,” he said in the statement.

Mekosuchine crocs are believed to have become extinct in Australia around 3,000 years ago. They may have lost much of their inland habitat due to encroaching dryland, a situation compounded by growing competition with other predators and the dwindling amount of prey, said co-author Michael Stein, a research associate at the University of New South Wales.

A backyard trove

The exact location of the discovery is a small town called Murgon, about three and a half hours’ drive from Brisbane, the capital of Queensland.

Archer said he and his colleagues had been excavating there since 1983, and he could still recall how it all began.

“UNSW colleague Henk Godhelp and I drove to Murgon, parked the car on the side of the road, grabbed our shovels, knocked on the door and asked if we could dig up their backyard,” he said.

The residents “grinned and said ‘of course’” after hearing their homes were sitting on some prehistoric treasures, Archer recalled.

“And, quite clearly, from the many fascinating animals that we’ve already found in this deposit since 1983, we know that with more digging there will be a lot more surprises to come,” he said.

It’s inherently difficult to identify an extinct species based on an eggshell, said Dean Lomax, a paleontologist and author of “The Secret Lives of Dinosaurs — Unearthing the Real Behaviors of Prehistoric Animals.” He wasn’t involved in the new research.

However, given that the eggshell was found in the same geological deposits and locality of the only known mekosuchine fossils from that period of time, Lomax said the authors made a solid argument.

“I think one of the key things here is that matching the fossil egg shells and the croc that laid them can provide new information,” he said. “It will help us to understand not only how they reproduced and where they laid their eggs, but the connection may help shed light on the lifestyle of these unusual crocs.”

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