Two works were presented in the 74th annual meeting of the Society of Vertebrate Palaeontologists (SVP) in Berlin. The first in the poster session and the second a oral presentation in the Temnospondyli symposium.
“The role of descriptive statistics in Finite Element Results: The Cingulata jaw as case of study” by Jordi Marcé-Nogué, Christian Escrig, Soledad De Esteban-Trivigno and Josep Fortuny is based in compute the average stress of the whole FEA model, which is a new approach that has been used recently in different works in order to obtain a single measurement that gives the researcher an idea of the relative strength of the structure. However, due to the nature of the FEA data, it needs to be fully developed taking into account the influence of the weight of the mesh in the results and trying to avoid the artificial noise produced in FEA due to the numerical singularities of the mesh. Consequently, new methodologies including, between other statistics, Mesh-Weighted Arithmetic Mean and Mesh-Weighted Median, are developed herein to make the results obtained in different models comparable, independently from the type and size of Finite Element mesh and avoiding the artificial noise in the results. These new indicators are firstly defined and tested in two-dimensional finite element models to latter be transferred to 3D models. In order to check their suitability, one Cingulata jaw has been used as case of study and solved using FEA with different meshes. Additionally, FEA has been applied in different members of Cingulata suborder, including eleven extant armadillo’s taxa, and three extinct taxa in order to evaluate and compare its biomechanical behaviour. Our results suggest that the proposed methodologies provide powerful indicators and that are suitable to use to compare different patterns of stress distribution. In particular, the new methods proposed are shown to be extremely useful when exploring the effect of the shape in the strength and the stiffness of vertebrate bone structures.
“3D computational modelling in stereospondyls (Temnospondyli): skull mechanics and ecomorphological implications” by Josep Fortuny and Jordi Marcé-Nogué is based in test the ecological role of these anamniote predators performing 3D Finite Element Analysis of Stereospondyl skulls using an extant phylogenetic bracket but also a comparison with extant eusuchia. These techniques allowed the evaluation of different ecological scenarios and to test different loading cases using volume scaled models that allowed the proper comparison of the results. Stereospondyls probably were able to feed under a bilateral bite, with stresses mainly on maxilla-nasal bones and interorbital regions. The posterior part of the skull present moderate levels of stress on the parietal-postparietal bones and occipital condyles, while on the palate the vomerine plate reveals important stresses. Interestingly, the cultriform process shows very low or any levels of stress in all the tested cases. Under a lateral loading to simulate how could hunt prey by using a rapid sideways sweep of the head during active swimming, the analyses show that these anamniotes presented very high levels of stress on the parasphenoid-exoccipital regions, but also in the whole vomerine plate may precluding these feeding behavior in most of the stereospondyl groups. In comparison with extant eusuchia, these anamniotes present different stress pattern showing that the absence of the secondary palate increases the levels of stress, especially on the snout and vomerine plate. Stereospondyls were also characterized for variable orbit position and size and FE results show that orbit position and size doesn’t affect the biomechanical capabilities of Stereospondyls. These anamniote animals were top predators on many continental ecosystems but were probably replaced during the Middle-Late Triassic by archosaur groups. This fact is probably due to the presence of different anatomical features as the development of secondary palate and high rostral shape diversity, especially on the lateral profile that increased its biomechanical capabilities.