Abstract

The noasaurid ceratosaur Kiyacursor longipes gen. et sp. nov. is described based on a fragmentary skeleton including cervical vertebra, pectoral girdle, humerus, and hind limbs from the Lower Cretaceous (Aptian) Ilek Formation at Shestakovo 1 locality in Western Siberia, Russia. This is the first ceratosaur from the Early Cretaceous of Asia, extending the stratigraphic range of Ceratosauria by 40 Mya on that continent. Kiyacursor shares unique hind limb proportions with Elaphrosaurus and Limusaurus suggesting improved cursorial ability. These taxa show an ostrich-like specialization of the pes, with the large third metatarsal and greatly reduced second metatarsal. In contrast, all other fast running non-avian theropod dinosaurs have the arctometatarsalian pes with the third metatarsal strongly reduced proximally. The new taxon lived in the Early Cretaceous ecosystem containing a number of other Jurassic relics, such as stem salamanders, protosuchian and shartegosuchid crocodyliforms, tritylodontid synapsids, and docodontan mammaliaforms.