NEW PROTOCOL FOR MUSCLE RECONSTRUCTION IN APPENDICULAR ELEMENTS OF TETRAPODS: A STUDY CASE APPLIED TO THEROPOD DINOSAURS

MESO, JORGE; POL, D.; PITTMAN, M.; QIN, Z.; DÍEZ DÍAZ, VERÓNICA; ARANCIAGA-ROLANDO, A. M.; MINER, S.; LECUONA, AGUSTINA; TROYELLI, A. ; MELCHOR, I. ; PALOMBI, D. ; SALGADO, LEONARDO; CITTON, PAOLO

General Roca

Jornada; Reunión de Comunicaciones de la Asociación Paleontológica Argentina (RCAPA); 2023

Asociación Paleontológica Argentina y Universidad Nacional de Rio Negro

The primary function of the forelimbs of non-avian theropod dinosaurs is associated with diverse and often very demanding tasks, such as feeding and social behavior. Among the different clades of non-avian theropods, there are radically different forelimb morphologies that result in a wide variety of functional specializations, as they reflect a basic appendicular design. Despite numerous publications on the forelimb of theropod dinosaurs, these mostly address topics such as its relative length and proportions, range of motion, and possible functionality. However, as acknowledged in previous studies, the forelimb must be studied as an integrated musculoskeletal system to better understand its biomechanical function. In this context, muscle reconstructions are an important tool for understanding different paleobiological aspects of extinct species, which have become increasingly common in recent years. Although integrative phylogenetic and extrapolatory analysis and Extant Phylogenetic Bracket (EPB) methods are useful toolkits for soft tissue reconstructions of extinct taxa, the literature reveals a persistent approach using two-dimensional drawings from high-resolution photographs. Here we propose a new protocol to reconstruct forelimb muscle a from high-resolution 3D models. Reliable models were made by digitizing several specimens using photogrammetry. To do this, around 350 to 500 photographs were taken of each element of the forelimb, and the set of resulting photographs was analyzed in the Agisoft Metashape software to create threedimensional models. Subsequently, digital elevation model (DEM) and contour maps were generated through the software ParaView, with the main goal of quantitatively evaluating the topography of each element. This procedure allowed us to more accurately delineate the cross-sectional area of muscle insertions. This is of particular interest since, together with reconstructions of extant species, it will allow us to quantitatively evaluate the different possible functional adaptations of the forelimb muscles of non-avian theropods on an ecomorphological framework.