The Carreras Pampa site in Bolivia’s Torotoro National Park is now the largest known dinosaur tracksite, with nearly 18,000 impressions across 1,321 trackways, including 16,600 three‑toed prints and 1,378 swim tracks. Most prints are "ghost tracks"—evenly spaced claw marks lacking heel impressions—consistent with bipedal theropods, although skeletal fossils are scarce. Exceptional preservation records walking, swimming and other behaviors and makes the site an ichnologic Lagerstätte of major scientific importance.
Record-Breaking ‘Ghost Tracks’: Nearly 18,000 Dinosaur Footprints Found in Bolivia
Archaeologists Found Nearly 18,000 ‘Ghost Tracks’Rafael Ben-Ari - Getty Images
Seventy million years ago the region that is now central Bolivia was a humid landscape of shallow freshwater lakes. At the edge of one such lake, groups of theropod dinosaurs repeatedly crossed soft mud, leaving long sequences of footprints and tail traces that were later buried and exquisitely preserved.
Today the Carreras Pampa tracksite in Torotoro National Park is the largest known dinosaur tracksite on record, yielding nearly 18,000 individual impressions. The Upper Cretaceous exposure contains 1,321 distinct trackways, including 16,600 three‑toed prints, 289 isolated impressions (some interpreted as tail drag marks), and 1,378 so‑called swim tracks found within 280 of those trackways.
What the Tracks Reveal
Paleontologist Raúl Esperante of the Geoscience Research Institute led the team that documented the site and published their results in PLOS ONE. "Bolivia has one of the most extensive and diverse records of dinosaur tracksites in the world," Esperante notes, while adding that published scientific analyses of many Bolivian sites remain limited.
Most of the prints at Carreras Pampa are described as "ghost tracks": evenly spaced claw impressions that lack clear heel marks. These tracks alternate left to right, show spacing consistent with bipedal walking, and appear alongside more distinct theropod prints—collectively pointing to theropod trackmakers rather than random surface markings.
Preservation—and the Lack of Bones
Although the site preserves an exceptional number of tracks, skeletal fossils are scarce. The processes that preserve soft‑sediment footprints—rapid burial of hardened mud—differ from those that bury carcasses. Animals that died near lake margins were likely scavenged, scattered by waves, or eroded before rapid burial could occur, while footprints became durable ichnofossils when sealed by subsequent sedimentation. Because many trackways were likely made by animals on the move, few individuals died in place, further reducing the chance of finding bones associated with the prints.
Track Types, Behavior, and Possible Trackmakers
Track morphotypes at Carreras Pampa vary. Some prints are exceptionally well preserved, showing claw marks, heel and pad impressions, and even the hallux (innermost toe). Others are elongated, deep traces associated with tail drags that preserve less anatomical detail. Overall, the overwhelming pattern is consistent with three‑toed theropod feet.
Without associated bones, precise species identification remains speculative. The researchers note similarities between some adult‑sized prints and the foot morphology of large theropods such as Tyrannosaurus and the ichnogenus Eubrontes, while smaller prints resemble Grallator‑type (juvenile or small theropod) tracks. Foot spacing and moderate toe splay indicate intermediate stride lengths characteristic of medium‑sized theropods, and wider toe spreading in some prints may reflect stability adaptations for moving across soft mud rather than high‑speed running.
Behavioral signals are preserved as well: many theropod trackways follow curved, meandering paths—typical of animals covering long distances—and show direction changes associated with brief pauses, interpreted as evasive maneuvers around obstacles or interactions with other animals. The site also preserves avian tracks and rosette‑shaped invertebrate burrows within some prints.
Swim Tracks and Ichnologic Significance
The site contains abundant swim tracks—elongated scratches and grooves made when clawed feet touched the rippled lakebed while animals were moving through water. Whether these were left by theropods, ancient crocodilians, or both remains uncertain. However, the dominance of theropod footprints across the site suggests that some theropods regularly entered the water or were competent swimmers.
"The swim tracks, tail traces, and avian tracks are remarkably well preserved, and most tracks are found in continuous trackways," Esperante said. "The abundance and exceptional preservation of these tracks and traces make the Carreras Pampa tracksite an ichnologic concentration and conservation Lagerstätte."
In sum, Carreras Pampa offers an unprecedented window into the movements, behaviors, and habitat use of Cretaceous theropods. Its nearly 18,000 traces provide both a numerical record and high‑quality behavioral snapshots that complement—but do not replace—the information normally provided by skeletal fossils.
