New data on the tyrannosauroid dinosaur Kileskus from the Middle Jurassic of Siberia, Russia

ABSTRACT

New postcranial bones (cervical and caudal vertebrae, chevron, fibula) of the proceratosaurid tyrannosauroid Kileskus aristotocus from the Middle Jurassic (Bathonian) Itat Formation at Berezovsk coal mine, Krasnoyarsk Territory, Western Siberia, Russia, reveal three possible autapomorphies of Kileskus: a deep anterior recess between the neural canal and prezygapophysis; a distinct pit at the base of the neural spine on the middle cervical vertebrae; and a ventral groove on the middle caudal vertebrae. Phylogenetic analysis recovered a nearly horizontal posterior centrodiapophyseal lamina in the anterior-middle cervicals with the infrapostzygapophyseal fossa located primarily dorsally to the lamina as a new synapomorphy for the Proceratosauridae. The deep oval fossa on the medial surface of the fibula with well-defined margins is a tyrannosauroid synapomorphy of Kileskus. In other Proceratosauridae the fibula is either absent or not described in detail. The longitudinal and reticular vascularization of the primary cortex in the Kileskus tibia suggests a slower growth rate compared with large-bodied tyrannosaurids.

KEYWORDS:

• Dinosauria
• theropoda
• Tyrannosauroidea
• Middle Jurassic
• Siberia
• Russia

Acknowledgments

For assistance in the field, we thank I. Danilov, D. Grigoriev, O. Shcheglova (Grigorieva), R. Hielscher, S. Ivantsov, K. Jäger, I. Kuzmin, M. Scheske, A. Schwermann, E. Syromyatnikova, and A. Valeev. We are grateful to E. Boitsova for preparing images of the histological sections and V. Kolchanov for preparing Figure 6. We thank the staff of the Saint Petersburg State University Research Centre for X-ray Diffraction Studies (St Petersburg, Russia) for their help with using the Leica 2500P microscope and for preparing images of the histological sections. The authors thank T. Carr, J. Canale, and an anonymous reviewer for providing helpful comments that improved the quality of the manuscript. Financial support was provided by the Deutsche Forschungsgemeinschaft (DFG) (grant MA 1643/14-1, 3), the Russian Foundation for Basic Research (project 11-04-91331-NNIO), and the Russian Science Foundation (project 19-14-00020). AA was also supported by the Zoological Institute, Russian Academy of Sciences (project АААА-А17-117022810195-3) and a Humboldt Research Award by the Alexander von Humboldt Foundation. The work was performed according to the Russian Government Program of Competitive Growth of Kazan Federal University.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Deutsche Forschungsgemeinschaft [MA 1643/14-1, 3]; Russian Science Foundation [19-14-00020]; Russian Fund of Basic Research (RFBR) [11-04-91331-NNIO].