Variation in the tail length of non-avian dinosaurs

ABSTRACT

Estimating the mass of an extinct organism is naturally difficult. Practicality and simplicity means that often some linear measurement is used as a proxy. In the case of non-avian dinosaurs, the total length of the animal (from the snout to the tip of the tail) is sometimes used for this purpose. However, the total length of the tail is unknown in all but very few dinosaurian taxa. Tail length data taken from specimens and the literature are shown here to have remarkable variation both between and within clades (and even within single species). Comparison with body length data shows that total length (including the tail) is therefore a less reliable measure of size than using the snout-vent length of the animal. ‘Snout-sacrum’ lengths are suggested as a more reliable alternative. Total length should not be abandoned, however, both to provide a comparison with older works and specimens lacking complete presacral axial columns, and for communication with the general public.

ACKNOWLEDGMENTS

My thanks to numerous colleagues who provided papers, discussions, and details of specimens with complete tails that are buried in the literature and research collections: A. Yates, P. Barrett, P. Dodson, P. Currie, V. Arbour, R. Redelstorff, M. Wedel, M. Taylor, J. Choiniere, P. Galton, D. Tanke, K. Tanoue, S. Nesbitt, A. Decceci, and C. Sullivan. Particular thanks are owed to S. Maidment both for discussions and for collecting data on a number of ornithischian specimens included here (especially those from North America), and also to A. Farke, C. Noto, and D. Henderson for detailed and constructive comments on the manuscript. Thanks to E. O’Gorman, M. Habib, and J. Yearsley for advice on the statistics. Thank to X. Xu, S. Chapman, and J.-L. Li for access to specimens in their care. This work was supported in part by the Chinese Academy of Sciences.

Handling editor: Patrick O’Connor