Dinosaur footprints frozen in sandstone reveal a sauropod strolling at 4 km/h. Slower than a human walk-suggesting these giants ambled rather than thundered.
A walk through the Cretaceous
On a sandstone slab in Savannakhet Province, a series of depressions preserves a moment from the Early Cretaceous period. These are not random features; they are the footprints, or ichnites, of dinosaurs that walked this land between 100 and 126 million years ago. The tracks are embedded in the Grès Supérieurs Formation, a layer of sandstone and mudstone that was once the soft mud of a riverbank or floodplain. The discovery includes tracks from sauropods, the long-necked herbivores, and possibly ornithopods.
The preservation of these tracks shows dinosaur behavior. The sauropod that left these prints was a member of the titanosauriforms, a group that includes some of the largest land animals ever to have lived. The prints are large, round impressions, consistent with the wide, pillar-like feet needed to support such immense weight. The distinct trail left by one of these giants allows for detailed scientific analysis, transforming simple footprints into a source of biomechanical data.
The science of a stroll
Ichnology, the study of trace fossils like footprints, allows scientists to calculate how fast a dinosaur was moving. The key measurements are the stride length—the distance between two consecutive prints from the same foot—and the footprint length itself. From the footprint size, paleontologists can estimate the animal's hip height, an important variable in the equation. A widely used formula, developed by biologist R. McNeill Alexander, relates stride length and hip height to calculate speed.
For the Phu Pha Thoep sauropod, the math reveals a walking speed of about 4 kilometers per hour. This is slower than an average human walking pace of 5 km/h. The data from this and other sauropod trackways suggests that these massive animals were not fast-moving creatures. They were likely slow, deliberate walkers, conserving energy as they moved through their ancient environment. The trackway tells a story of a calm, unhurried progression, unlike cinematic depictions of thundering herds. Other dinosaurs identified from fossils in the same geological formation include the sauropod Tangvayosaurus hoffeti and the predatory spinosaurid Ichthyovenator laosensis.
💡Fun Facts
Ichnology is the specific branch of paleontology dedicated to studying trace fossils, including footprints, burrows, and fossilized feces (coprolites).
The Grès Supérieurs Formation in Laos is the geological equivalent of the Khok Kruat Formation in Thailand, which also contains abundant dinosaur fossils.
Besides sauropods, tracks of two-legged ornithopod dinosaurs have also been identified in the Grès Supérieurs Formation.
The first dinosaur discovered in Laos, a sauropod named *Titanosaurus falloti*, was identified from bones found in the same rock formation in 1936.
The trackway is in a generally accessible area, but it is best visited during daylight hours. The nearby Phu Pha Thoep National Park in Thailand is open daily from 7:30 AM to 5:30 PM.
Admission
Free.
Accessibility
The site is on an exposed, uneven rock surface. Access may require walking over rocky terrain. Sturdy footwear is recommended.