A Jurassic lakeshore
In the Kokpek Pass, southeast of Almaty, slabs of tan sandstone are tilted at a severe angle against the sky. Embedded in these rocks are dozens of fossilized footprints. These are not the tracks of a single, lost animal, but a congregation. The site preserves a moment from the Middle Jurassic, approximately 165 million years ago, when this mountainous region was a vast, wet floodplain surrounding a lake.
The tracks were pressed into the soft, muddy substrate of the lakeshore by a group of young sauropod dinosaurs. The fine-grained sediment was ideal for capturing the shape and texture of their feet, and subsequent layers of sand and silt buried the prints before they could erode. Over millions of years, these layers lithified into the solid sandstone seen today. The immense tectonic forces that created the modern Tian Shan mountain range later uplifted and tilted these Jurassic beds, exposing the ancient surface for discovery. The quality of preservation allows paleontologists to study the behavior of animals that have been extinct for eons. Other Jurassic deposits in Kazakhstan, like the Karabastau Formation, are known for preserving a variety of fossils, including insects and pterosaurs in similar lakebed environments.
Evidence in stone
The Kokpek Pass tracksite is an important location for understanding dinosaur behavior. The footprints are all of a similar, small size, indicating they were made by juvenile animals. Critically, the trackways run parallel to one another, showing that the entire group was moving in the same direction. This parallel movement is among the strongest pieces of evidence for herding behavior in dinosaurs. Much like modern elephants, these giant herbivores likely traveled in groups, and the young may have been kept together for protection.
While no adult tracks are found in the same layer, the presence of a juvenile-only herd suggests a complex social structure. This could have been a prehistoric nursery, where younger sauropods stayed together while the larger adults foraged elsewhere. The concept of dinosaurs as social, caring parents is a departure from older views of them as solitary reptiles. Fossil trackways, or ichnofossils, are unique in that they record the actions of living animals, providing information that skeletal remains cannot. Similar sites in Texas and Colorado in the United States also show clear evidence of sauropods moving in coordinated herds. The sauropods of Middle Jurassic Central Asia were diverse, with relatives of well-known dinosaurs like Mamenchisaurus inhabiting the region. The Kokpek tracks show the social dynamics of these immense creatures.