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A new Lower Cretaceous dinosaur from Uzbekistan, Ulughbegsaurus uzbekistanensis, has been described from a single jaw fossil. The research team led by the University of Tsukuba estimated that this carcharodontosaur weighed over 1,000 kg and was 7.5-8.0 meters long, far longer than previously described predators of the same formation. The age, location and co-occurrence of the fossil with the small tyrannosaurid Timurlengia shed light on the transition from carcharodontosaurians to tyrannosaurids occupying the top predator niche. Credit: University of Tsukuba
University of Tsukuba researchers described new lower upper apex predator Cretaceous from Central Asia, Ulughbegsaurus uzbekistanensis, which coexisted with a smaller tyrannosauroid.
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 Upper 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 approximately 7.5-8.0 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 takes its name from 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, carcharodontosaurians liked Ulughbegsaurus disappeared 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 at the Hokkaido University The museum explains “The discovery of Ulughbegsaurus uzbekistanensis fills an important gap in the fossil record, revealing that carcharodontosaurs were widespread across the continent, from 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.
Reference: “A new carcharodontosaurian theropod dinosaur occupies a predator niche in early Upper Cretaceous Uzbekistan” by Kohei Tanaka, Otabek Ulugbek Ogli Anvarov, Darla K. Zelenitsky, Akhmadjon Shayakubovich Ahmedshaev and Yoshitsugu Kobayashi, September 8, 2021 Royal Society Open Science.
DOI: 10.1098 / rsos.210923
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