Walking like giants: the evolution of Form and Function of the locomotive posture in Titanosauria (Dinosauria, Sauropoda)

Abstract

Sauropods are a group of dinosaurs easily recognizable by their body plan, constituted of long necks and tails, and four columnar limbs. Another important factor was the acquisition of a large body mass, which was only possible thanks to anatomical changes, involving mainly the fore and hind limbs, thus causing a better distribution of mass. These changes would be accentuated in the lineage of Titanosaurs, a diverse group throughout the Cretaceous, mainly in South America, and which are now considered the largest land animals that ever lived. Based on ichnological (such as footprint studies) and anatomical analyses, it has been established that the gigantism present in titanosaurs was only possible thanks to a change in body posture, starting from a narrow-gauge pattern - where both hand and foot footprints approach each other. or they intersect in the midline - for as instance known as wide-gauge, where the footprints are moved away from the midline, caused by changes in the humerus and femurs of these animals. In spite of being the main change to allow the corporal increase, it is still a little studied factor, lacking mainly of analyzes that use methods that can be empirically tested; so that the different hypotheses proposed previously can also be verified. To try to fill precisely these gaps in knowledge, the project proposed here aims to analyze in a combined way the change in the Form and Function of the limbs of these animals. The first step will be the digitization of the specimens that will be used, through the photogrammetry technique. These selected specimens will then have their musculature and associated structures (such as cartilage and tendons) reconstructed, so that they can be used in the following steps. The change in shape will be evaluated using Geometric Morphometry, in order to understand how the anatomy of the limbs of these animals changed with the different postures. Function evaluation will be done through Finite Element Analysis, a technique that allows simulating how muscles would react to different internal and external forces that these elements would need to withstand. The use of Finite Element Analysis, or its combination with Geometric Morphometry, represents so far, an unprecedented method for the study of this change in posture. Therefore, results are expected that can fill the different knowledge gaps involving the biomechanical aspects of this group, and elucidate a little more on how these animals became the largest terrestrial beings that ever lived.