55-Million-Year-Old Crocodilian Eggshells Reveal They May Have Pounced on Prey From Trees

Scientists have discovered the oldest known crocodilian eggshells in a grazier’s backyard. The fossils are around 55 million years old and belong to a group of ancient crocs called mekosuchines — some of which are thought to have dropped from trees and hunted prey like modern-day leopards.

“These eggshells have given us a glimpse of the intimate life history of mekosuchines,” Xavier Panadès i Blas, lead author of the paper, said in a statement.

“We can now investigate not only the strange anatomy of these crocs, but also how they reproduced and adapted to changing environments,” Panadès i Blas continued.

The eggshells, described for the first time in the Journal of Vertebrate Paleontology, were found in Murgon, Queensland, approximately 168 miles (270 kilometers) northwest of Brisbane, Australia.

Read More: 70-Million-Year-Old Dinosaur Egg Reveals Ancient Nesting Clues

Who was Wakkaoolithus godthelpi?

Today, Murgon is a small rural town, nestled between farmland and bushland. Fifty-five million years ago, the area would have been covered in swamps surrounded by lush forests, according to the researchers.

The unassuming clay pit where the eggshells were found was once a shallow swamp or lake, and is now one of the country’s oldest fossil sites.

Paleontologists have been excavating the pit for more than four decades. The digs have led to the discovery of what may be the world’s earliest known songbird and the oldest bat in the southern hemisphere, not to mention a plethora of other fauna, including salamanders, ancient marsupials, and turtles.

For this study, the researchers examined the microstructure of 12 eggshells originally collected in the 1990s. Their analysis reveals that elements of the eggshells show greater similarity to those of alligators and caimans than those of modern crocodiles, but contain notable differences from all three.

The eggshell type has since been named Wakkaoolithus godthelpi — in recognition of the Wakka Wakka First Nations people on whose land the eggshells were found, and Henk Godthelp, in honor of his involvement at the Murgon site. The name also draws on Latin, specifically “oolithus,” which combines the Latin words for egg (“ova”) and stone (“lithus”).

Mekosuchines: Ancient Relatives Of Modern-Day Crocs

Mekosuchines thrived in what is now Australia, dominating the landscape long before modern crocodiles appeared. Australia, which was then still attached to Antarctica and South America, was home to several species, ranging from Mekosuchus inexpectatus to species that may have been semi-arboreal (meaning they spent some of their lives on trees), such as Trilophosuchus rackhami.

“Some were also apparently at least partly semi-arboreal ‘drop crocs’,” UNSW palaeontologist Professor Michael Archer said in a statement.

“They were perhaps hunting like leopards — dropping out of trees on any unsuspecting thing they fancied for dinner.”

The eggshells are thought to belong to a genus called Kambara, which are among the earliest species of mekosuchines and the only ones known to have existed in and around the fossil site.

According to the Australian Museum, members of the Kambara genus were broad-snouted, generalist feeders that feasted on small vertebrates, including mammals and turtles. The researchers describe the crocs as “semi-aquatic ambush predators.”

The eggshells may also offer clues to the local environment, research associate Michael David Stein, who was involved in the project, wrote in an article for The Conversation. Specifically, there is relatively little evidence of bacterial degradation, suggesting the nest may have experienced dry periods. The researchers say this could mean Kambara living at the site timed hatchings with the start of the wet season.

Don’t Put Your Egg(Shells) All In One Basket

While eggshells may not get the airtime that skeletal remains do, the researchers say this study highlights their value as a paleontological resource that can offer insights into the nesting and breeding behavior of the species that laid them.

“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,” said Panadès i Blas.

Read More: A Stash of Leathery Dinosaur Eggs Tells Us About the Origins of the Giant Reptiles

Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article: