The Bissekty Formation of Uzbekistan is not the most talked-about rock formation in Asia. However it has done a good job of revealing some lesser-known animals from a lesser-known time in dinosaurian history. The animals here date back to the very beginnings of the Late Cretaceous, roughly 90 to 85 million years ago. During this time there was a greenhouse effect caused by global warming across the planet.
The Cretaceous Thermal Maximum, as it is known, was probably caused by a tectonic rifting of the Atlantic Ocean during this period. This geological event caused the release of a massive quantity of greenhouse gases. It was also a time when some recognizable elements were appearing in the dinosaur fauna of the time. Bissekty clearly shows many animals that would later rise to dominance of the end-Cretaceous world.
The environment preserved here is described as being composed of several biomes. These range from brackish coastal habitats to freshwater deposits farther inland. Altogether the formation covers a large swathe of time and preserves a massive array of both vertebrate and invertebrate life typical for this time. Also, a braided river system ran in between Bissekty and the sea. Today, this vast area is the Kyzyl Kum Desert of Uzbekistan.
During much of the Cretaceous, a large inland sea called the Turgai Sea dominated large parts of Eurasia, especially in the Central Asia region. It also split Europe into a series of islands, serving as a dividing barrier between Europe and Asia.
Several crocodylomorphs are known from Bissekty's rocks although hardly any of them are very well known in the public consciousness. Biggest among these is the mighty Kansajsuchus, also the largest predator in the Bissekty environment.
It was not related to modern crocodiles. Instead it was a goniopholidid, a separate and extinct offshoot from the croc line. For one, they had two pairs of bony scutes or osteoderms on their backs. Goniopholidids even had armor on their bellies. Plus, the limbs of goniopholidids were rather long, with the forelimbs being longer than the hindlimbs.
Kansajsuchus is known from parts of its skull, legs and armor. It is thought to have been 8 meters in length, larger than modern saltwater crocodiles. At this size it could tackle any prey items that came its way, including the dinosaurs in its habitat.
Azhdarcho is Bissekty's only pterosaur. It was the founding member of the azhdarchid family as a whole. This medium-sized pterosaur was at least 2 meters in height and had a 4.5-meter wingspan. Azhdarcho was also one of the medium-sized predators of the formation, taking on animals that it could fit into its jaws. Like all azhdarchids it likely stayed away from water, instead preferring to hunt on dry ground.
The main herbivores here included medium-sized duckbill ancestors like Levnesovia. This animal is known from skull remains as well as some body fossils like vertebrae. Levnesovia was one of the earliest known hadrosauroids, or ancestral duckbills. It was described in 2009 by Hans-Dieter Sues and Alexander Amerianov, and published in the Proceedings of the Royal Society.
The only armored dinosaur known from Bissekty is Bissektipelta. It is known only from parts of its skull, so everything else must be inferred from its relatives. Like its fellow nodosaurid armored dinosaurs, Bissektipelta lacked a clubbed tail. It was however a very well-armored animal with a wide body and squat, short legs. It also browsed low vegetation just around a meter or so off the ground.
The most recently described dinosaur from the Bissekty is Timurlengia, also the formation's top dinosaur predator. Called Timurlengia euotica, it was described this year by a team comprising Steve Brusatte and colleagues. It was an ancestral tyrannosaur. The find was important in fully understanding the evolutionary history of the tyrannosaurs, and in unveiling the secrets of their sensory arsenal.
Timurlengia already showed the developed eyesight and sense of smell of its descendants. These would be features that would be carried until the end of the Dinosaur Age, reaching their ultimate form in Tyrannosaurus. Timurlengia, named after the Mongol conqueror and emperor Timur, was a horse-sized predator. It was just a little more than 4 meters in length.
It already had the big head of later tyrannosaurs although its teeth were more blade-like than the bone-crushing clubs of its descendants. Timurlengia even had the short but strong two-fingered hands of later tyrannosaurs. This showed that the typical tyrant dinosaur features had begun to show up even before their increase in body size.
Much lower on the size scale were the birdlike dinosaurs of the area. One in particular was Urbacodon, a tiny troodontid. Urbacodon was a tiny omnivore that raced around the forest floor, eating anything that it could catch. It is known from parts of its jaw and teeth.
Another tiny omnivore is Caenagnathasia, a tiny oviraptorosaur. Caenagnathasia is also among the smallest non-avian dinosaurs, growing just 60 centimeters long. It is known from jaws that are a mere 7 centimeters in length. It too would have run around the forest floor, eating anything it could. Unlike Urbacodon though, Caenagnathasia lacked teeth and instead had a hard beak.
The final of these fragmentary non-avian theropods is Itemirus. This animal was a small dromaeosaur, or "raptor" dinosaur. It was a relative of the famous Velociraptor and probably behaved similarly. Itemirus is known from fragmentary skull remains.
Numerous birds have been found here, especially species of enantiornithes. Bissekty is one of the best places for this extinct bird group, most of which seem to have been concentrated around lakeside and riverside forest deposits.
Enantiorninithine birds had teeth in their jaws and lacked any hard beaks. They also lacked the pygostyle of stiffened tail feathers of modern birds. The enantiornithes found here are all small generalist feeders, growing as big as small pigeons or sparrows. They had well-developed fingers with claws still present on their hands.
Just as there were duckbill and tyrannosaur ancestors at Bissekty, there was also a well-known horned dinosaur ancestor. Turanoceratops is a 2-meter horned dinosaur and one of the only Asian horned dinosaurs to have brow horns. In this respect it looked like a scaled-down Triceratops the size of a sheep.
It was also similar to, and closely related to the North American Zuniceratops from around the same time. However it was just half Zuniceratops' size. Turanoceratops was a transitional form between the very primitive Asian horned dinosaurs and more advanced forms like Triceratops and kin.
Fragmentary titanosaur remains are known from Bissekty. Currently they are far too incomplete to assign to any genus.
