View from ground (left) and from high above (right). Image from the study.

Finding dinosaurs is a mixture of knowing where to look and pure luck. It typically involves paleontologists hiking for miles through promising places, their eyes glued to the ground, scanning for the tiniest fragment of fossilized bone. Sometimes, they’ll look for “float” — bits of fossil that have eroded out of a hillside. If they find some, they follow the trail up the slope, hoping to find the source: a bone, a skeleton, or an entire bonebed.

But even to the trained eye, it’s a slow, painstaking process.

There’s only so much ground you can cover, and there are only so many experienced paleontologists. Even for the most prolific ones, discoveries are often serendipitous. But now, researchers have an unlikely ally: lichen.

A team of scientists led by Brian J. Pickles from the University of Reading paid attention to a tiny, overlooked clue. They found that a specific, vibrant orange lichen loves to grow on dinosaur bones. That lichen, it turns out, can be spotted from above using drones.

“This research highlights how modern organisms can help us to find ancient ones,” Pickles said in a press release.” It’s remarkable to consider that these lichens, essentially miniature ecosystems, are founded upon the remains of dinosaurs that died over 75 million years ago. Using drone technology to detect the spectral signatures of the lichens could potentially revolutionize how paleontologists search for fossils.”

Orange You Glad You Found Me?

The test site was none other than Dinosaur Provincial Park (DPP) in Alberta, Canada. This is a UNESCO World Heritage Site, universally recognized as one of the richest deposits of Late Cretaceous dinosaur fossils on the planet. Walk through its alien landscape of gullies and hoodoos, and you are walking on the 75-million-year-old graves of giants. But pinpointing their exact location is still a challenge.

The team learned that two lichen species (Rusavskia elegans and Xanthomendoza trachyphylla) colonized as much as 50% of exposed bone fossils, but less than 1% the surrounding rock fragments. The team confirmed this through repeated surveys.

There’s a good reason why they do. Although dinosaur bones underwent intense chemical transformations, they’re still different from the surrounding rock matrix. In this case, the fossils provide alkaline, calcium-rich, and porous substrates that these lichens favor. They love the chemistry, they love the texture, and when they get a chance, they grow right on top of the fossils.

This isn’t entirely a new find, says Dr. Caleb Brown, from the Royal Tyrrell Museum of Paleontology in Canada. But it’s surprising just how much the lichens favor fossils.

“This pattern of lichen growing preferentially on fossil bone has been noted for decades, but never quantified until now. When first encountering high concentrations of exposed fossil bone-like bonebeds, it is often the ‘meadow’ of orange lichen that is noticed first, not the bones themselves.”

Location, Location, Location

Using drones with specialized sensors and cameras, the team successfully identified lichen-colonized fossils from aerial images. With the naked eye, they’re not so easy to spot. But look at it with different wavelengths, and they really stand out. Simply put, the lichens act as a neon sign that can help researchers find promising areas for fossils.

They then put the method to the test. They flew the drone 30 meters above a known bone bed and then fed the data into an “unsupervised classification algorithm”. This is a type of artificial intelligence you don’t have to pre-train. You just tell it: “Find the statistically weird stuff.” The algorithm immediately zeroed in on the lichen’s unique spectral signature. The results were perfect. The computer processed the drone image and spat out a new map where every pixel “positively detected” as lichen-on-bone was flagged.

Remarkably, paleontologist Darren H. Tanke speculated something like this back in 1980. Tanke went even further: he thought fossil bones could be detected by satellites.

His prediction wasn’t spot on, but it had a fantastic idea to it. With drones, and with a proxy (the lichen), we’re closer than ever to making airborne fossil hunting happen. In fact, Derek Peddle, part of the remote sensing team from the University of Lethbridge said satellites could also detect lichen in some areas.

“This drone study lays the groundwork for mapping much larger areas using aircraft and satellites. The new lichen indicators we’ve developed will help us find fossils across vast landscapes. It’s exciting to combine our imaging technology with this international team’s expertise to advance dinosaur discovery through remote sensing of lichen.”

A Useful Tool

This doesn’t mean “boot leather science” is dead. A drone can’t excavate a Tyrannosaurus rex. You still need the human experts on the ground with their brushes, plaster, and deep anatomical knowledge. But this new method can be important for reducing the time spent surveying the ground and eliminating the “luck”. It directs the limited, precious time of field crews to the places that matter most. It turns a search for a needle in a haystack into a directed, statistical search.

And this is very likely not applicable to just the dinosaurs in Alberta. The specific orange lichen might not grow on bones in the Gobi Desert or Patagonia, but the strategy is now proven. Scientists worldwide can now start searching for their own local indicators. Is there a specific moss that thrives on the mineral profile of mammoth bones in Siberia? A desert shrub whose roots preferentially seek out fossil-rich layers? Species of bacteria that form a visible film on marine reptile fossils?

This paper is a starting gun, telling scientists worldwide to stop looking for just the bones and start looking for the life that loves the bones.

The study was published in Cell Reports.