Abstract
A number of different approaches are currently available to digitally restore the symmetry of a specimen deformed by taphonomic processes. These tools include mirroring and retrodeformation to approximate the original shape of an object by symmetrisation. Retrodeformation has the potential to return a rather faithful representation of the original shape, but its power is limited by the availability of bilateral landmarks. A recent protocol proposed by Schlager and colleagues (2018) overcomes this issue by using bilateral landmarks and curves as well as semilandmarks. Here we applied this protocol to the Middle Pleistocene human cranium from Steinheim (Germany), the holotype of an abandoned species named Homo steinheimensis. The peculiar morphology of this fossil, associated with the taphonomic deformation of the entire cranium and the lack of a large portion of the right side of the face, has given rise to different hypotheses over its phylogenetic position. The reconstruction presented here sheds new light on the taphonomic origin of some features observed on this crucial specimen and results in a morphology consistent with its attribution to the Neanderthal lineage.
Highlights
The study of fossil specimens has been revolutionised by the foundation of modern morphometrics [1]
Symmetry offers the possibility to restore the original shapes of fossil remains that are found broken or incomplete [6,7]
We suggest that the peculiar facial morphology of Steinheim is mostly a result of the crushing that occurred in the upper portion of the midface (Figure 2b)
Summary
The study of fossil specimens has been revolutionised by the foundation of modern morphometrics [1]. Symmetry offers the possibility to restore the original shapes of fossil remains that are found broken or incomplete [6,7] This is key to the interpretation of these specimens, since taphonomic alteration affecting diagnostic features may lead to incorrect taxonomic attributions and dubious phylogenetic reconstructions [7,8,9]. Specimens can be handled in a safe, virtual environment [7] and undergo restoration protocols that can include the realignment of dislocated fragments [13,14,15,16] or the digital removal of the plaster from traditional reconstructions [8,17] without the risk of damaging the original material These protocols can be associated with symmetrisation, which helps to recreate missing portions or ‘undo’ the effects of plastic deformation. The application of retrodeformation can be affected by the state of preservation of the object [4]
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