Evolutionary disparity in the endoneurocranial configuration between small and gigantic tyrannosauroids

ABSTRACT

In extinct archosaurs, brain proportions have been inferred from the morphology of fossilized endocasts. Here we provide the first neurocranial and paleoneurological description of the basal, small-bodied tyrannosauroid Dilong paradoxus compared with larger tyrannosaurids, like Tyrannosaurus rex. Dilong differs from other tyrannosauroids in the proportions of cerebral and cerebellar regions, morphology of venous sinuses, and superimposed position of the forebrain relative to the rest of the endocast. Whereas endocasts of Tyrannosaurus show a more linear configuration and likely contained within a thick intersticial space, the endocast of Dilong indicates an S-shaped brain protected by thinner meninges. Based on our statistic analysis and comparisons with modern crocodilians, we hypothesize that increased body size likely imposed a new spatial configuration for development of the central nervous system during the evolution of gigantism in tyrannosaurs.

KEYWORDS:

• Dinosauria
• tyrannosauroidea
• endocast
• brain
• evolution

Acknowledgments

We thank P. Makovicky for consulting with us the scan parameters of the Tyrannosaurus Sue (FMNH). Amy Balanoff and Stephen Brusatte pre-reviewed an earlier version of drafts and greatly improved the manuscript with their critical comments and suggestions. This work was supported by the grant of Center for Interdisciplinary Biosciences, Technology and Innovation Park, University of Pavol Jozef Šafárik in Košice (Slovakia)‚ the National Natural Science Foundation of China (41120124002 and 41688103), and the Czech Science Foundation (P302/12/1207).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Grantová Agentura České Republiky [P302/12/1207];National Natural Science Foundation of China [41120124002 and 41688103];Center for Interdisciplinary Biosciences, Technology and Innovation Park, University of Pavol Jozef Šafárik in Košice

Notes on contributors

Martin Kundrát

Martin Kundrát, X.X., and Y.G. designed the project, D.C. performed the CT scanning. M.K. analyzed and interpreted the results, and wrote the paper. M.K. performed the 3D modelling. M.H., A.G. and M.K. conducted geometric morphometrics and biostatistics analysis.