Ninety million years ago, this arid desert was a humid coastal plain where advanced crocodiles preyed on young dinosaurs.
A Cretaceous coastline in the desert
The dusty plains of the Kyzylkum Desert hold a secret from a much wetter, warmer world. Ninety million years ago, during the Turonian stage of the Late Cretaceous, this region was a lush, swampy coastal flatland on the edge of the ancient Tethys Sea. The fossil-bearing rocks of this vanished ecosystem are known as the Bissekty Formation, a layer of sandstone and conglomerate up to 80 meters thick. These deposits preserve one of Eurasia's richest collections of terrestrial fossils from this period, showing a "greenhouse" world.
The environment was a network of braided rivers, deltas, and estuaries with varying levels of salinity. The climate was hot and humid, supporting a diverse community of life. Thousands of isolated bones and teeth from this period have been recovered from the Bissekty Formation since paleontological work began in the 1970s, showing the animals that lived and died along this ancient coastline.
The apex predator of the floodplain
The largest predator in this ecosystem was not a dinosaur. It was a massive crocodylomorph named Kansajsuchus. While related to modern crocodiles, Kansajsuchus belonged to an extinct side-branch of neosuchians called goniopholidids. These were advanced, semi-aquatic reptiles, and Kansajsuchus was one of the largest, estimated to reach lengths of 5 to 7 meters. Its anatomy, known from skull fragments, vertebrae, and armor plates called osteoderms, shows it lived as an ambush predator in the region's many waterways.
The Bissekty Formation has also yielded fossils of other crocodylomorphs, like the smaller Tadzhikosuchus, but Kansajsuchus was the apex predator of the water. Its powerful jaws and robust build made it capable of taking down large prey, including the unwary dinosaurs that came to the water's edge to drink.
A world of dinosaurs
The prey for Kansajsuchus was abundant. The Bissekty Formation is famous for its diverse dinosaur fauna. These include the two-meter-long horned dinosaur Turanoceratops, which resembled a small Triceratops, and early duck-billed dinosaurs, or hadrosauroids, like Levnesovia.
The local theropods were larger. The Bissekty fauna includes Timurlengia euotica, a horse-sized precursor to the giant tyrannosaurs that already possessed the advanced brain and sensory features of its later relatives. Another large predator was the recently identified Ulughbegsaurus uzbekistanensis, a carcharodontosaur that would have competed with Timurlengia for food. The area also had smaller predators like dromaeosaurs ("raptors") and the ostrich-like ornithomimids. The high concentration of fossilized remains from juvenile dinosaurs suggests that the young were particularly vulnerable, making them frequent targets for the giant crocodylomorphs lurking in the water.
💡Fun Facts
The name *Kansajsuchus* comes from the Kansai locality in Tajikistan where the first fossils of the genus were discovered.
The Bissekty Formation has produced one of the most diverse faunas of Late Cretaceous placental mammals and their relatives in the world.
*Timurlengia*, the local tyrannosauroid, is named after the 14th-century Central Asian ruler Timur, also known as Tamerlane.
Fossils of pterosaurs, specifically the azhdarchid *Azhdarcho lancicollis*, show that flying reptiles with wingspans of 4.5 meters shared the skies above this ancient coast.