CSI: Cretaceous — A Reptile 'Body Farm' Sheds New Light on How Dinosaurs Decayed

In April 2023, graduate student Hannah Maddox drove 13 hours from Knoxville, Tennessee, to a U.S. Geological Survey station in Everglades National Park to collect 30 frozen Argentine black and white tegus that had been culled to limit the invasive lizards’ spread. She returned the following year to retrieve another 30.

Researcher Stephanie Drumheller-Horton, a paleoecologist at the University of Tennessee, organized the project to study a surprising gap in scientific knowledge: how reptiles decompose. Tegus were ideal subjects because they have a generic lizard morphology, were available through donations, and could be used ethically without killing animals for research.

On a humid May day the team laid thawing tegus into a rectangular frame roughly the size of a coffin, built from pressure-treated lumber and hardware cloth. Since then, across seasons, Drumheller-Horton and her students have watched those lizards fall apart in unprecedented detail, documenting the sequence of tissue loss, microbial change, and insect activity.

Why this matters

Understanding modern reptile decomposition has broad implications for paleontology. It can help explain why some fossils preserve fragile soft tissues, why many dinosaur skeletons are found headless, and why the classic dinosaur 'death pose' — an arched neck and curled tail — occurs so often. Until now, most decomposition studies have focused on mammals, leaving important blind spots when scientists extrapolate to reptiles and extinct dinosaurs.

From museum puzzles to experimental tests

Interest in reptile decay intensified after Drumheller-Horton examined Dakota, an exceptionally preserved Edmontosaurus discovered in the Hell Creek Formation. Dakota showed bite marks, degloving injuries, and a deflated foot consistent with prolonged postmortem exposure. Those observations suggested multiple pathways to soft-tissue preservation, challenging the assumption that only rapid burial or immediate desiccation produce mummified remains.

Peer reviewers of the Dakota study urged more foundational work on lizard decay, which helped spur the tegu experiment. Paleontologist Mary Schweitzer and others have noted that controlled, real-time experiments can test variables the fossil record cannot, such as local microbial communities and brief chemical conditions that influence preservation.

How the experiment is run

The project sits on a quiet hilltop behind the university agricultural fields, sheltered by pine trees. The first set of 30 tegus became the 'summer box'; the second set, collected in February 2024, became the 'winter box'. In spring 2025 the team expanded the study with four alligators (including an 11-foot individual placed in its own container) and two dismembered dwarf crocodiles, donated by a nuisance hunter and a zoo, respectively.

Students and collaborators sample the carcasses regularly. Graduate student Hannah Noel, working with environmental microbiologist Jennifer DeBruyn, swabs skin and soils to track microbial and geochemical shifts. Each week Drumheller-Horton clips a tegu toe to monitor changes in skin, nail, and soft tissue; samples are frozen immediately and later sectioned microscopically to chart which tissues break down first.

Early findings

Initial observations reveal striking seasonal and anatomical patterns. Tegus in the winter box purge internal contents far more slowly than those in the summer box, where insect activity accelerates internal decomposition. Active microbial digestion proceeds faster in warm conditions, which can destroy skin sooner; colder conditions slow internal decay and can leave skin intact for longer. Large crocodilians decompose more slowly overall, likely because of their mass.

The study has already produced plausible mechanical explanations for the 'death pose'. In the summer box, drying skin can pull the head back and raise the tail as tissues desiccate, suggesting that simple physical forces during decomposition may recreate the posture seen in many fossil specimens. The absence of the same pattern in the winter box hints that climate and seasonality influence whether that pose develops.

Another consistent pattern is rapid head disarticulation. Insects access underlying soft tissues via natural openings — eyes, nose, and mouth — accelerating decay around the skull. Reptile skulls are made of many unfused bones held together by soft tissue, so they disarticulate more readily than mammal skulls. That architectural difference may help explain why many fossil skeletons lack heads.

Implications and next steps

Rather than delivering single, definitive answers, the tegu project is reframing how scientists think about fossil preservation. Early results show multiple pathways to preserved soft tissue and challenge the notion that one process explains all exceptional fossils. As Drumheller-Horton puts it, answering one question often reveals many more to explore.

The team plans to scale the experiment to include different lizard species, more crocodilians, turtles, and birds to assess how anatomy and environment shape decomposition and potential fossilization pathways. For now, students and researchers will keep returning to the hilltop, sampling skin, soil, and toes to trace exactly how these creatures fall apart and what that reveals about the deep past.

Key contributors: Hannah Maddox, Stephanie Drumheller-Horton, Hannah Noel, Jennifer DeBruyn, Owen Singleton, Clint Boyd, Mary Schweitzer.