Abstract
Carcharodontosauria is a group of medium to large-sized predatory theropods, distributed worldwide during the Cretaceous. These theropods were probably the apex predators of Asiamerica in the early Late Cretaceous prior to the ascent of tyrannosaurids, although few Laurasian species are known from this time due to a poor rock record. Here, we describe Ulughbegsaurus uzbekistanensis gen. et sp. nov. from the early Late Cretaceous (Turonian) of Central Asia, which represents the first record of a Late Cretaceous carcharodontosaurian from the region. This new taxon is represented by a large, isolated maxilla from the Bissekty Formation of the Kyzylkum Desert, the Republic of Uzbekistan, a formation yielding a rich and diverse assemblage of dinosaurs and other vertebrates from fragmentary remains. Comparison of the maxilla with that of other allosauroids indicates Ulughbegsaurus was 7.5–8 m in body length and greater than 1000 kg in body mass, suggesting it was the previously unrecognized apex predator of the Bissekty ecosystem while smaller known tryannosauroids and dromaeosaurids were probable mesopredators. The discovery of Ulughbegsaurus records the geologically latest stratigraphic co-occurrence of carcharodontosaurid and tyrannosauroid dinosaurs from Laurasia, and evidence indicates carcharodontosaurians remained the dominant predators relative to tyrannosauroids, at least in Asia, as late as the Turonian.
Highlights
Allosauroids were globally distributed medium to large predatory theropods that dominated various ecosystems during the Middle Jurassic to the end Cretaceous
We describe a new Late Cretaceous (Turonian) specimen of a relatively large-bodied carcharodontosaurian, represented by an isolated maxilla, from the Bissekty Formation of the Republic of Uzbekistan, Central Asia
Within the rich and diverse dinosaur fauna of the Bissekty Formation (e.g. [12,13,14,15,16,17,18,19]), our discovery of this predatory theropod Ulughbegsaurus, at 7.5–8.0 m in length and greater than 1000 kg in mass, probably occupied the role of apex predator in this Turonian ecosystem
Summary
Considered as the apex predators in Laurasia until the mid-Cretaceous [1,4], carcharodontosaurians and other large-bodied theropods (ceratosaurids and spinosaurids) disappeared after which tyrannosauroids (primarily tyrannosaurids) occupied top predatory niches during the last 20 million years of the Cretaceous (Campanian and Maastrichtian). The disappearance of carcharodontosaurians and other allosauroids at the end Turonian is probably related to the ascent of tyrannosauroids, as tyrannosaurids, in Late Cretaceous ecosystems of Asiamerica [5]. Species of carcharodontosaurians have been recovered from two lower Upper Cretaceous formations (Cenomanian and Turonian) of Asiamerica and include large taxa [5,6]. Our discovery adds to few known Late Cretaceous carcharodontosaurian species from Asiamerica and reveals a previously unknown apex predator among mid-sized predatory tyrannosauroids and dromaeosaurids in the Turonian Bissekty ecosystem. Institutional abbreviations: CCMGE, Chernyshev’s Central Museum of Geological Exploration, Saint Petersburg, Russia; UzSGM, State Geological Museum of the State Committee of the Republic of Uzbekistan on Geology and Mineral Resources, Tashkent, Uzbekistan; ZIN PH, Paleontological Collection, Zoological Institute, Russian Academy of Science, Saint Petersburg, Russia
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