CSI: Cretaceous. A reptile body farm is shedding light on how dinosaurs died.
Here’s how scientists are solving the “dinosaur death pose” mystery and others.
One bright day in April 2023, Hannah Maddox drove 13 hours from Knoxville, Tennessee, to a U.S. Geological Survey (USGS) research station in the Everglades National Park, near the southern bump of Florida. Her mission was simple: Collect 30 frozen, dead Argentine black and white dead tegus, culled as part of a broad effort to curtail the invasive lizards’ spread. The next year, she repeated the journey to collect 30 more.
“I did do two cannonball runs to the Everglades and back,” she laughs. “And we thank you for that,” says paleoecologist Stephanie Drumheller-Horton, who sent Maddox, a graduate student at the University of Tennessee, to fetch the tegus.
Tegus make adorable pets but destructive members of the Everglades community. “They eat anything they can, including protected groups of animals,” says Drumheller-Horton. But their appetites were not what made the reptiles interesting to her.
The tegus checked two boxes for an unusual experiment that Drumheller-Horton and Maddox were about to launch back in Knoxville. First, the adorable invasives have a “very sort of generic lizard shape,” Drumheller-Horton says, and second, they were available. She didn’t want to kill any animals for the research, and USGS researchers had agreed to freeze, store, and donate the dead animals.
On a muggy day in May, they laid out the thawing, dead lizards in a box a little larger than a coffin, made from a frame of pressure-treated two-by-fours with walls of hardware cloth. Ever since, as season gives over to season, Drumheller-Horton and her students have been watching the creatures fall apart—a process that’s never been so closely studied before. These tegus will help answer a basic science question: How do reptiles decompose?
It’s a major gap in our understanding of nature’s relentless recycling program that has big ramifications: physically big, but also scientifically big. A detailed description of how modern lizards decay could also help reveal ways that ancient ones became fossils.
National Geographic History Magazine
The decaying reptiles could solve several of paleontology’s biggest mysteries from why some fossils preserve fragile soft tissues that would otherwise decay to why so many dinosaurs are missing their heads or end up in the classic “death pose”—a fairly common posture where the head of the dino, or bird, arches violently backward and the tail curves over the body. The posture has stoked vigorous debate for decades, and researchers have argued for myriad explanations ranging from the force of water moving through the area to neurological conditions to the contraction of ligaments. Knowing how an animal ended up in this position may point to how it died.
Drumheller-Horton suspects that for some of these open questions, there’s no one explanation that excludes the rest, but as an experimentalist she thinks the best way to understand the reptile death process may be to watch it unfold in real time.
Reptile death remains a mystery
We know in broad strokes how plant litter decomposes, how a succession of worms, beetles, millipedes, woodlice, and other bugs break everything down into small pieces. Then fungi and other microbes find, harvest, digest, and repurpose the nitrogen and carbon molecules, making it available to other plants and animals. We also know the general sequence of how human beings fall apart, and how that tracks with the season of death, the availability of bugs, and the climate. Forensic anthropologists have done that work in service of decoding a decaying body to learn how, when, and where the person died—and whether there was foul play.
Much of the early work in the field came from experiments in which decomposing pigs were laid out in natural settings to rot. In the last half-century, more detailed studies have come out of “Body Farms,” research facilities where scientists study the decaying bodies of human donors. The first one, the Forensic Anthropology Center at the University of Tennessee, launched in the early 1970s. There are now eight in the U.S. and more abroad.
But reptiles? Scientists know very little, says Drumheller-Horton. Whatever they hypothesize about decaying reptiles—including dinosaurs—is drawn from existing work on mammals. “It’s all focused on mammals,” she says, half-exasperated. “Which is fine. I get it. We live in the age of mammals.”
But mammals and reptiles, obviously, are not biologically identical, and that narrow focus gave rise to research blind spots like understanding how the entire organism falls apart. Decades ago, many scientists assumed soft tissue like blood, muscle, and skin degraded too quickly to be preserved during fossilization. That changed in 2005, when North Carolina State University paleontologist Mary Schweitzer reported the identification of blood vessels in a T. rex fossil. That work fueled a hunt for preserved soft tissue and fueled scientific interest in how it changed during fossilization.
Even today, “in paleontology, the majority of the time, you’re finding the hard parts” of the creature, Drumheller-Horton says. “We’ll start with that, instead of looking at how the soft tissue actually interact with it.”
Her decaying tegu experiment explores the issue from the other direction, tracking the changes in soft tissue—and all other tissues—as dead reptiles decompose. Doing so, she says, may help show how soft tissue ended up in ancient fossils.
Schweitzer herself sees experiments like the tegu body farm as essential to solving the soft tissue mystery. “There’s all kinds of factors that come into play that we don’t have the ability to test in the fossil record,” she says, that can be explored in a real-time experiment like Drumheller-Horton’s.
From bites to burials
The black box of reptile decay first became a roadblock for Drumheller-Horton back in 2017.
For most of her scientific career, she’s focused not on recent decay but on taphonomy, the study of how dead things become fossils, from the Greek word for “burial.” In paleontology communities, she has become known as a fossil expert on biting, revealing who hunted whom and using those insights to identify new species. “It’s a good way to talk about diet and behavior, and how do we reconstruct food webs and things like that,” she says.
In 2017, she received a call out of the blue from paleontologist Clint Boyd at the North Dakota Geological Survey. “He’s like, I want to invite you to work on a project, but I can’t tell you what it is until you agree to work on it,” she says. “Somebody bit somebody,” she thought to herself.
It was true: Something had bitten Dakota, a well-preserved, duck-billed dinosaur called Edmontosaurus found in 1999 in the Hell Creek Formation, in North Dakota, with traces of skin and nails. Its exceptional soft tissue remains put Dakota in the category of rare fossils known as “dinosaur mummies,” where fossilized skin impressions or other signs of soft tissue surround the animal’s skeleton. The fossil also preserved telling bite marks on the tail and arm.
(What are dinosaur mummies? Read more about the rare fossils.)
When Drumheller-Horton arrived at the scene, she found evidence of what forensic anthropologists call a “degloving” injury, which means that the skin had been peeled back and turned inside out, like removing a dinner glove from an arm. The bite had also extended to the bone; ultimately, she found evidence of at least two predators that had left their impression on Dakota.
The scientists then examined a foot that looked suspiciously deflated—especially considering how much muscle mass the dinosaur would have needed to stand up and run at close to 30 miles per hour. The deflated dino-paw looked familiar, like deflation phenomena she’d seen on the human bodies at the university’s Body Farm, caused by microorganisms during decomposition. That meant that not only had something tried to eat Dakota; it was likely that Dakota, postmortem, had been exposed to the elements for a considerable amount of time. Until then, most paleontologists hypothesized that soft tissue was only preserved if the dead dino was buried or dried out immediately after death, preventing microbes from devouring the squishy parts. But Dakota’s skin hadn’t completely decayed.
“That’s what got this conversation going,” she says. “We throw around this term dinosaur mummy, and it makes it sound like there’s just one recipe. Now we’re realizing there are multiple different pathways for how you can get nicely preserved … dinosaur skin.”
Boyd notes that in the years since they first published their Dakota results in 2022, further analyses—including CT scans of the dinosaur’s hand—suggest that soft tissue, like skin, can be mineralized with iron oxide, along with the bone. “These tissues might be more common in the fossil record than we realize,” he says. But someone trying to preserve a thin-skinned animal who is focused on the bones, he says, may inadvertently chip off the skin to get there. “It’s very hard to recognize that it's present before you destroy it,” says Boyd.
During the peer-review process for their original Dakota paper, other researchers dinged the team for citing mammal decomposition studies to support new ideas about reptile “mummification.” “They said we needed more foundational work on how lizards decay,” Drumheller-Horton says. “But we don’t have it.”
Not yet, anyway. But Drumheller-Horton says those dead tegus decomposing on a hillside in Tennessee can fill in the gaps.
Building a reptile body farm
The experiment is tucked away on a quiet hilltop behind the university’s agricultural research fields and encircled by tall pine trees. “We’re like the lowest maintenance tenants ever,” she says. “We’re like, don’t touch it, don’t mow it.”
The box with the original set of 30 tegus became the “summer box,” while the second batch of 30 dead, frozen lizards that Maddox secured in February 2024 populated the “winter box.” In the spring of 2025, they expanded their rotting bestiary by adding four alligators—one measuring 11 feet long, so big that it got its own box—and two dismembered dwarf crocodiles. The alligators came from a nuisance alligator hunter in Georgia, and the donated crocs had died of natural causes at a zoo.
The decomposing reptiles are rarely alone. A graduate student named Hannah Noel, working with environmental microbiologist Jennifer DeBruyn, comes by to swab the skin and sample the soil to study microbial and geochemical changes. Every week, Drumheller-Horton goes to the hilltop and snips off a tegu toe to measure changes in the skin, nail, and tissue; the samples go directly into deep freeze to avoid degradation before they can be analyzed. Eventually, the toes will be shaved into thin sections and studied to determine which tissues are decomposing in what order.
Owen Singleton, an undergraduate researcher on the team, has been tracking differences between the boxes and found, not surprisingly, that the tegus in the winter box “are not purging” their innards as fast as those in the summer box, which were aided by the activity of bugs. As a result, active decomposition—the part where internal microbes digest an organism from the inside out—is taking longer and destroying more of the skin. They’ve also observed that decomposition is taking longer for the crocodilians, likely because of their enormous size.
Clues to the dino death pose and other mysteries
There’s also the issue of that “death pose” and its origins. Already, in the tegu summer box, Maddox has observed that drying skin seems to pull tegu heads back and raise their tails, suggesting an almost mechanical explanation for the pose. (They haven’t found the same evidence in the winter box, which hints, but doesn’t prove, that the death stance may be more common in dinos that die during warm conditions.) The process of decomposition itself may help shape the final, fossilized form of dinosaur, but not in ways that scientists used to believe—namely, by removing the soft tissue.
Early observations are illuminating other mysteries. Tegu heads are disarticulating—the bones are falling apart—more quickly than the rest of the body partly because insects have better access. “Insects don’t really care about the skin. They want the soft tissue that’s underneath, so they’re going to take advantage of naturally occurring body openings,” Drumheller-Horton says. “So the eyes, the nose, the mouth.”
In addition, reptilian heads are composed of a puzzle of bones held together by soft tissue and not fused into one big mass, like human skulls, which means they fall apart more easily. That observation of fast decay may help explain why beautifully preserved dinosaur fossils often lack their heads.
Broadly, however, the experiment’s initial observations point less toward definitive answers about dino mummies and other fossil enigmas and more toward challenging the notion that we understand the process. They are overturning the idea that one process can explain how and why we find fossils the way we do. “But that’s just science,” says Drumheller-Horton. “You answer one question, and it just coughs up like 30 more questions that you now need to chase down.”
The next step in the project is to scale up, literally, even beyond the boxes now perched on the hilltop. “We would love to throw out a whole bunch of other lizards,” she says, “a whole bunch of crocodilians like some turtles, or some birds, and just see what happens.” And for the foreseeable future, she says, she’ll be leading colleagues and students to the hilltop to open the boxes, crouch down, try not to breathe too deeply, and clip some reptilian toes, to track exactly how the creatures fall apart.
