A Jurassic Reptile Was Once Thought To Swim, But It Actually Climbed Trees
A 166-million-year-old reptile that lived during the time of the dinosaurs was believed to have swum in ancient lagoons, but new research has revealed that it actually climbed trees.
The Middle Jurassic, which lasted from around 174 to 161 million years ago, was a critical time for evolution. Many groups of animals on Earth were diversifying into new forms. However, fossils from this period are incredibly rare.
Most research has focused on the dinosaurs from this time, so the small reptiles that lived alongside them are often overlooked. Their fossils are usually tiny and badly damaged, making it a challenge to learn about their lives.
One of these species is Marmoretta oxoniensis, which is known from some fossils discovered in Oxfordshire and the Isle of Skye.
They were found alongside the remains of a variety of marine life, so it was assumed that Marmoretta was a semi-aquatic reptile. But modern scanning techniques have showed that it lived in the trees instead.
“It’s important not just to find out that a species exists, but how it lived,” said Dr. David Ford, the lead researcher.
“By studying animals like Marmoretta, we can infer what was happening during divergences in the evolution of reptiles.”
Marmoretta is a stem lepidosaur, an early relative of the group containing all snakes and lizards. Lepidosaurs are one of the two main reptile groups alongside the archosaurs, which include crocodiles, dinosaurs, and birds.
The lepidosaurs and archosaurs are thought to have split apart around 260 million years ago during the Late Permian.
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Fossils of both groups are poorly preserved. Extracting them from rock often causes more damage because they are so fragile.
Now, technology has advanced enough for researchers to investigate bone fragments while they’re still embedded in rock.
The Marmoretta fossils included a skull that was two centimeters long and finger bones that were just millimeters long.
“If we’d prepared this tiny fossil traditionally, we never would have understood the ecology of Marmoretta,” said Dr. Ford.
“By using synchrotron scanning, we were able to get incredibly fine resolution that has allowed us to draw new conclusions about its lifestyle.”
When the team examined the scans of the fossil, they noticed that the hands did not belong to an aquatic reptile.
During this period, aquatic reptiles would have had flattened fingers or webbing to paddle through the water with.
Marmoretta has long, curved bones near the end of its fingers, which is a sign of climbing reptiles. The curves help them grip the tree trunk and branches. Its spine also would have been stiffer than those of aquatic reptiles for balance when climbing up high.
After comparing the measurements of its bones with living reptiles, the researchers concluded that Marmoretta did spend time in the trees around the edge of a subtropical lagoon. It appears that Marmoretta and its relatives moved aboveground to avoid potential predators.
The study was published in the Proceedings of the Royal Society B.
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