Who was king before the tyrannosaurus? Uzbek fossil reveals new top dino

Iconic tyrannosauroids like T. rex dominated the top of the food chain at the end of the dinosaur reign. But they did not always occupy this first place.

In a new study published in Royal Society Open Science, a research team led by the University of Tsukuba described a new genus and species belonging to Carcharodontosauria, a group of medium to large carnivorous dinosaurs that predated tyrannosauroids as top predators.

The new dinosaur, named Ulughbegsaurus uzbekistanensis, was found in the Lower Cretaceous Bissekty Formation of the Kyzylkum Desert in Uzbekistan, and therefore lived around 90 million years ago. Two separate evolutionary analyzes support the classification of the new dinosaur as the first definitive carcharodontosaurian discovered in the Late Cretaceous of Central Asia.

“We described this new genus and this new species on the basis of a single isolated fossil, a left jaw or an upper jaw,” says the study’s first author, Assistant Professor Kohei Tanaka. “In theropod dinosaurs, jawbone size can be used to estimate animal size because it correlates with femur length, a well-established indicator of body size. Thus, we were able to estimate that Ulughbegsaurus uzbekistanensis had a mass of over 1000 kg and was about 7.5 to 8.0 meters long, more than the length of an adult African elephant. “

This size greatly exceeds that of any other known carnivore of the Bissekty Formation, including the small tyrannosauroid Timurlengia described in the same formation. Therefore, the newly named dinosaur likely dominated the food web in its early Late Cretaceous ecosystem.

The namesake of the genre is worthily majestic; Ulughbegsaurus is named after Ulugh Beg, 15th-century mathematician, astronomer and sultan of the Timurid Empire of Central Asia. The species is named after the country where the fossil was found.

Before the Late Cretaceous, carcharodontosaurs like Ulughbegsaurus became extinct from the Paleocontinent which included Central Asia. This demise is believed to be related to the rise of tyrannosauroids as top predators, but this transition has remained poorly understood due to the paucity of relevant fossils.

Lead author Professor Yoshitsugu Kobayashi of the Hokkaido University Museum explains: “The discovery of Ulughbegsaurus uzbekistanensis fills an important gap in the fossil record, revealing that carcharodontosaurians were widespread across the continent, from l ‘Europe to East Asia. As one of the last surviving Carcharodontosaurians in Laurasia, the coexistence of this large predator with a smaller tyrannosauroid reveals significant stresses on the transition from the predator niche to the Upper Cretaceous summit. ”