DOI: 10.5061/dryad.5qb8387
title: Data from: The function(s) of the bone ornamentation in the crocodylomorph osteoderms: a biomechanical model based on a finite element analysis

description: This paper aims at assessing the influence of the bone ornamentation and,
 specifically, of the associated loss of bone mass on the mechanical
 response of the crocodylomorph osteoderms. To this aim, we have performed
 three dimensional modeling and finite element analyses on a sample which
 includes both extant dry bones and well-preserved fossils tracing back to
 the Late Triassic. We simulated an external attack under variable angles
 on the apical surface of each osteoderm and further repeated the
 simulation on an equivalent set of smoothed 3D-modeled osteoderms. The
 comparative results evidenced that the presence of an apical sculpture has
 no significant influence on the von Mises stress distribution in the
 osteoderm volume although it involves a slight increase in its numerical
 score. Moreover, performing parametric analyses, we evidenced that the
 Young’s modulus in the osteoderm which may vary depending on the bone
 porosity, the collagen fiber orientation or the calcification density has
 no impact on the von Mises stress distribution inside the osteoderm
 volume. As the crocodylomorph bone ornamentation is continuously remodeled
 by pit resorption and secondary bone deposit, we assume that the apical
 sculpture may be the outcome of a “trade-off” between the bone mechanical
 resistance and the implication in physiological functions. These
 physiological functions are indeed based on the set-up of a bone
 superficial vessel network and/or on the recurrent release of mineral
 elements into the plasma: heat transfers when basking and respiratory
 acidosis buffering during prolonged apnea in neosuchians and teleosaurids;
 compensatory homeostasis in response to general calcium deficiencies. On a
 general morphological aspect, the osteoderm geometrical variability within
 our sample lead us to assess that the global osteoderm geometry (whether
 square or rectangular) does not influence the von Mises stress whereas the
 presence of a dorsal keel would rather reduce the stress along the
 vertical axis.
description: Supplementary Figure
 1Presentation of the
 3D-models: the sampled ornamented osteoderms (A, C, E, G, I, K) and their
 smoothed version (B, D, F, H, J, L). The original surface of the 3D
 envelopes was comprised between 500k and 2 million triangles for each
 specimen after the scan or the photogrammetry acquisition. After we
 rescaled all the obtained 3D-objects to the same centroid size (as
 detailed in the text), we simplified the surface and reduced the number of
 surface triangles to a value comprised between 20k and 30k using the
 remeshing tools of Geomagic studio 12 along the following steps: 1) “quick
 smooth”: a tool which homogenizes the mesh into similar triangles (size
 and shape) while having no significant incidence on the resulting
 morphology. 2) “decimate”: a tool which allows to obtain a reduction of
 the mesh while not deteriorating the details of the surface. The resulting
 mesh is visible on the figure for each model. X: the transversal axis; Y:
 the longitudinal axis; Z: the vertical axis. The scale bars refer to the
 size of the 3D objects after the scale modification which leads all
 specimens to share the same centroid size (see text for
 details).Supplementary
 Figure1.tifSupplementary Figure
 2Convergence study with
 respect to the mesh size. Numerical results obtained for the Caiman
 crocodilus ornamented model (vertical force, reference values of the
 modeling parameters) using different mesh sizes; a star denotes the model
 presented in this study. VF1: high-stress volume fraction corresponding to
 a threshold of σ1 = 100 MPa (which roughly corresponds to the strength of
 compact bone). VF2: high-stress volume fraction corresponding to a
 threshold of σ2 = σ1/ 2.Supplementary
 Figure2.tifSupplementary Figure
 3Parametric analysis in
 Caiman crocodilus with respect to the number of adjacent osteoderms (N).
 A: Average von Mises stress in the osteoderm. B: high-stress volume
 fractions VF1 (blue line, right side scale) and VF2 (purple line, left
 side scale). Relevant reference parameters are: Eo = 10 GPa (Young’s
 modulus of the osteoderm); Eb = 0.1 GPa (Young’s modulus of the basal
 tissue); α = 0° and λ = 0° (Force orientation).Supplementary
 Figure3.tif