Evaluation of a New Method of Fossil Retrodeformation by Symmetrization: Crania of Papionins (Primates, Cercopithecidae) As a Test Case

Diagenetic distortion can be a major obstacle to collecting quantitative shape data on paleontological specimens, especially for three-dimensional geometric morphometric analysis. Here we utilize the recently -published algorithmic symmetrization method of fossil reconstruction and compare it to the more traditional reflection & averaging approach. In order to have an objective test of this method, five casts of a female cranium of Papio hamadryas kindae were manually deformed while the plaster hardened. These were subsequently ‘‘retrodeformed’’ using both algorithmic symmetrization and reflection & averaging and then compared to the original, undeformed specimen. We found that in all cases, algorithmic retrodeformation improved the shape of the deformed cranium and in four out of five cases, the algorithmically symmetrized crania were more similar in shape to the original crania than the reflected & averaged reconstructions. In three out of five cases, the difference between the algorithmically symmetrized crania and the original cranium could be contained within the magnitude of variation among individuals in a single subspecies of Papio. Instances of asymmetric distortion, such as breakage on one side, or bending in the axis of symmetry, were well handled, whereas symmetrical distortion remained uncorrected. This technique was further tested on a naturally deformed and fossilized cranium of Paradolichopithecus arvernensis. Results, based on a principal components analysis and Procrustes distances, showed that the algorithmically symmetrized Paradolichopithecus cranium was more similar to other, less-deformed crania from the same species than was the original. These results illustrate the efficacy of this method of retrodeformation by algorithmic symmetrization for the correction of asymmetrical distortion in fossils. Symmetrical distortion remains a problem for all currently developed methods of retrodeformation. Citation: Tallman M, Amenta N, Delson E, Frost SR, Ghosh D, et al. (2014) Evaluation of a New Method of Fossil Retrodeformation by Algorithmic Symmetrization: Crania of Papionins (Primates, Cercopithecidae) as a Test Case. PLoS ONE 9(7): e100833. doi:10.1371/journal.pone. 0100833 Editor: Kornelius Kupczik, Max Planck Institute for Evolutionary Anthropology, Germany Received March 15, 2014; Accepted May 29, 2014; Published July 3, 2014 Copyright: 2014 Tallman et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. Data, including scans, on our retrodeformations are available for download at http://www.cs. ucdavis.edu/,amenta/retrodef.html. Comparative data are available at http://primo.nycep. org/. Funding: This research was supported, in part, by National Science Foundation grants 05-13894 and 11-17663 (to N.A.), 99-82351, 05-13660 and 11-16921 (to E.D.); Professional Staff Congress-City University of New York Faculty Research Award Program grants 669381, 664333 and 665407 (to E.D.); and National Science Foundation Integrative Graduate Education and Research Traineeship grants 03-33415 and 09-66166 (to E.D. for NYCEP). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: Dr. Deboshmita Ghosh works at Stratovan Corporation but no competing interests exist. This does not alter the authors’ adherence to the PLOS ONE policies on dating sharing and materials. * Email: tallmame@gvsu.edu