‘These weird crocs were all over the place’: Australia’s oldest crocodile eggshells unearthed in Queensland back yard | Crocodiles

Scientists have identified what are believed to be the oldest crocodilian eggshells ever found in Australia, discovered in a breeder’s backyard in regional Queensland.

The 55 million-year-old eggshells – found in a fossil bed at Murgon, about 270km northwest of Brisbane – likely belong to a group of extinct crocodiles known as mekosuchines, new research suggests.

Modern saltwater and freshwater crocodiles arrived in Australia about 3.8 million years ago. “Before they got here, these strange mekosuchine crocodiles were everywhere,” said study co-author Professor Michael Archer, a paleontologist at the University of New South Wales.

Some mekosuchines were partial tree-dwellers, such as the crest-headed crocodile, nicknamed the “falling crocodile” because it could have climbed trees and dropped onto animals passing below.

“The idea of ​​’dropped fangs’ isn’t as crazy as it sounds. We probably had crocodiles spending time in trees and jumping on their prey,” Archer said.

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Fossil eggshells found at Murgon likely belonged to an earlier genus of mekosuchines known as Kambara.

“We know we’re looking at the oldest crocodile egg shells in Australia… Kambara The mekosuchines are the first we know of of this whole group,” Archer said.

The research focused on 12 fossil eggshells that were collected accidentally over several years in the 1990s, but were only recently analyzed by the study’s lead author, Dr. Xavier Panadès i Blas of the Catalan Institute of Paleontology Miquel Crusafont in Barcelona.

He said eggshells “preserving the microstructural and geochemical signals that tell us not only what types of animals laid them, but also where they nested and how they reproduced.”

“Eggshells should be a routine and standard part of paleontological research – collected, preserved and analyzed alongside bones and teeth,” he said in a statement.

The structure of mekosuchine eggshells “is unlike any other crocodilian eggshell”, Archer said, highlighting their association with a group of crocodiles unique to Australia.

“We still don’t know what the relationship of this group of crocodiles is to all the other crocodiles in the world. All we know is that when saltwater and freshwater crocodiles entered Australia… it was the beginning of the end for this particular group.”

Dr Matthew McCurry, a vertebrate palaeontologist at the Australian Museum who was not involved in the research, said the mekosuchines were “representative of the fact that crocodiles of the past did much more than in modern ecosystems”.

“If we go back to the Cretaceous [period, 66m to 143m years ago]crocodiles did a multitude of different things: some were entirely marine and had paddle-shaped limbs, others fed exclusively on plants,” he said.

“When most people think of paleontology, they think of the bones and teeth of organisms – these are often the parts that fossilize most easily. Tracks are probably the second most common thing… prints left behind.”

“We occasionally find bones from these animals, but eggs are comparatively rarer.”

The study was published in the Journal of Vertebrate Paleontology.