A predator posse in stone
In 1996, two young girls discovered a set of unusual impressions on a sandstone slab in what is now Phu Faek Forest Park. Geologists confirmed these were the footprints of large, meat-eating dinosaurs, preserved for 140 million years. The tracks are embedded in the Phra Wihan Formation, a layer of sandstone deposited by ancient braided rivers during the Early Cretaceous period. This formation is part of the larger Khorat Group, a series of rock layers that makes northeastern Thailand one of the most important dinosaur fossil regions in Southeast Asia.
The main tracksite at Phu Faek reveals 21 individual footprints across six different pathways. One trackway is particularly compelling, showing seven three-toed prints moving in the same southeastern direction. The largest of these prints measure 45 centimeters long and 40 centimeters wide, with strides between 110 and 120 centimeters. The parallel movement of multiple animals shows gregarious, or group, behavior. The variation in the size of the prints suggests the group may have consisted of both adults and younger individuals, moving together as a pack.
The Khorat ecosystem
The dinosaurs that made these tracks were likely large carnosaurs, a group of sizable bipedal predators. Some studies propose a link to Siamotyrannus isanensis, a theropod whose name means "Siamese tyrant" and whose fossils were also found in the Khorat Plateau. While Siamotyrannus was initially considered a relative of T-Rex, further analysis places it among the metriacanthosaurids or allosaurids. More recent finds in the area from 2023 include over 10 footprints from a smaller carnivorous dinosaur estimated to be around 2 meters tall and 5 meters long.
The Khorat Plateau was home to carnivores. The same geological formations that preserved the theropod tracks have also yielded the first sauropod tracks found in Thailand. Fossils of other dinosaurs, such as the spinosaurid Siamosaurus suteethorni, have also been identified, primarily from teeth. The presence of tracks from large predators, long-necked herbivores (sauropods), and other dinosaurs shows a complex and active ecosystem during the Early Cretaceous.