Forgotten Shark Jaws Are Now a Goldmine for Ocean Science

How a new study unlocked decades of hidden data from preserved shark and ray jaws in museum collections

Years ago, while helping catalog specimens at a natural history museum, I remember unboxing a broad-nosed seven-gill shark jaw. After decades in the museum collection, it was yellowed and a little chipped, but still fierce-looking. 

It had been in storage since the 1980s, labeled with a handwritten tag and with no backstory beyond where it was caught. I remember thinking, “If only you could talk.” Like many others, that jaw was carefully stored, hoping it would someday help scientists advance our understanding of life on Earth.

Fast forward to now, and it turns out that those jaws can talk. Scientists just hadn’t asked the right questions yet.

A new study led by Dr Laura Holmes at Flinders University, in collaboration with the University of Tasmania, flips the script on how we think about shark jaws in museum and private collections. 

Published in Marine Environmental Research, the study confirms that even chemically treated jaws — cleaned with ethanol, bleach, or hydrogen peroxide — can still be used for stable isotope analysis. 

In simple terms, this means researchers can use jaws collected decades ago to determine what sharks were eating and where they were feeding.

This is big news, especially for rare or protected species, where getting tissue samples is tricky and often not ethical or even legal. Think of it this way: Imagine being able to understand the past diet of great whites or tiger sharks from decades ago just by studying their teeth. It’s like reading their travel logs and dinner menus all in one.

So how does it work? The researchers analyzed teeth from three species with very different tooth shapes and structures: cownose rays, gummy sharks, and sevengill sharks. They treated the jaws with common preservation chemicals or left them untreated as controls. Then, they examined the carbon (δ¹³C), nitrogen (δ¹⁵N), and sulfur (δ³⁴S) isotope values in the teeth using a technique called stable isotope analysis.

To put it in perspective, these isotope ratios are like the fingerprints of diet and habitat. Carbon tells you where in the water column an animal fed. For example, whether they hunted near the coast or out at sea.

 Nitrogen helps pinpoint their place in the food chain (i.e. were they top predators?). Sulfur, which tends to reflect the source of dietary protein, adds another layer to the puzzle.

The key question was whether those preservation chemicals, used to make the jaws last longer and look prettier, would affect the results. The answer? They don’t.

“Finding that preservation chemicals had no impact on isotope values opens the door for the use of jaws from historic collections across Australia and globally,” said Flinders University research associate Dr. Lauren Meyer.

That’s huge. Museums and even private trophy collections around the world contain preserved shark and ray jaws, many collected in the ’70s, ’80s, and ’90s, before stricter protections were in place—some date from 19th-century expeditions. 

Until now, these were mostly seen as educational tools or curiosities. After all, they thought that chemical treatment made them useless. However, this research has turned them into scientific goldmines.

And it’s not just about sharks. “This study opens the door to use a tremendous resource of samples to untangle the current and historic diet and foraging habitats of complex predators,” added Dr. Meyer. That includes animals like killer whales, sperm whales, and fur seals, species for which we might have historic jaw specimens but no other biological data.

For someone who’s worked both in labs and in conservation nonprofits, this kind of shift in perspective hits home. I’ve sat in meetings where data gaps made it nearly impossible to design solid conservation plans. We’d often say, “If only we had data from before fishing pressure increased,” or “If only we knew how their diet changed over time.” 

Well, it turns out we might have had that data all along, tucked away behind glass.

Of course, there are limits. The study found that while carbon and nitrogen isotopes held up well even after six months of chemical exposure, sulfur values were a little less stable over time. But even so, having access to carbon and nitrogen data alone from decades-old samples is already a win.

The authors also developed a protocol for acid-treating shark teeth to remove inorganic material because not all shark teeth are created equal. Some are soft, and some are dense, and the acid bath needs to be adjusted accordingly. This detail might sound trivial, but it’s the kind of technical hurdle that often blocks a method from being widely adopted. 

By providing clear steps, the team has made it easier for other labs to replicate and build on this work.

From an ecological perspective, this isn’t just a story about shark diets. It’s a story about how we can use the past to understand the present and better plan for the future. 

Sharks are keystone predators. Their movements and feeding habits ripple through entire ecosystems. Understanding how those patterns have shifted over the last 50 years could help us spot changes driven by overfishing, climate change, or habitat degradation.

There’s also something hopeful here. Conservation can feel like it’s always reacting to crises, always one step behind. But studies like this remind us that the past isn’t lost. Sometimes, the tools for understanding it are already in our hands… or on a dusty museum shelf.

That old sevengill jaw I encountered years ago? Now, I see it differently. It’s not just a relic. It’s a record. And it might still have something to say.

Published in Fossils et al. Follow to learn more about Paleontology and Evolution.

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Best,

Sílvia P-M, PhD Climate Ages