DOI: 10.5061/dryad.tx95x6b52
title: The evolution of femoral morphology in giant non-avian theropod dinosaurs

description: Theropods are obligate bipedal dinosaurs that appeared 230 million years
 ago and are still extant as birds. Their history is characterized by
 extreme variations in body mass, with gigantism evolving convergently
 between many lineages. However, no quantification of hindlimb functional
 morphology has shown if these body mass increases led to similar
 specializations between distinct lineages. Here we studied femoral shape
 variation across 41 species of theropods (n= 68 specimens) using a
 high-density 3D geometric morphometric approach. We demonstrated that the
 heaviest theropods evolved wider epiphyses and a more distally located
 fourth trochanter, as previously demonstrated in early archosaurs, along
 with an upturned femoral head and a mediodistal crest that extended
 proximally along the shaft. Phylogenetically informed analyses highlighted
 that these traits evolved convergently within six major theropod lineages,
 regardless of their maximum body mass. Conversely, the most gracile femora
 were distinct from the rest of the dataset, which we interpret as a
 femoral specialization to “miniaturization” evolving close to the bird
 lineage (Avialae). Our results support a gradual evolution of known
 “avian” features, such as the fusion between lesser and greater
 trochanters and a reduction of the epiphyses’ offset, independently from
 body mass variations, which may relate to a more “avian” type of
 locomotion (more knee- than hip-driven). The distinction between body mass
 variations and a more “avian” locomotion is represented by a decoupling in
 the mediodistal crest morphology, whose biomechanical nature should be
 studied to better understand the importance of its functional role in
 gigantism, miniaturization and higher parasagittal abilities.
description: # The evolution of femoral morphology in giant non-avian theropod
 dinosaurs Give a brief
 summary of dataset contents, contextualized in experimental procedures and
 results. This dataset contains : 1\)
 Pintore_etal_2024-Supplementary_figures_and_tables.docx — A text document
 including Supplementary Figures and Supplementary Tables. 2\)
 Pintore_et_al_2024-Branch_lengths_sensitivity_analysis.xlsx — An Excel
 sheet including a sensitivity analysis comparing phylogenetically based
 statistical analyses from tree with equal vs time-calibrated branch
 length. 3\)
 Pintore_et_al_2024-Supporting_Information_sensitivity_analysis.docx — A
 text document including a discussion of the sensitivity analysis comparing
 the impact of using different types of branch length computation ##
 Description of the data and file structure 1\) Figure S1 illustrates the
 sensitivity analyses of variation between logMDC (Minimal Circumference of
 the femoral Diaphysis) and estimated body masses; Figure S2 displays the
 successful repeatability testing of the ability of the operator to
 reproduce the same landmark configurations on different specimens; Figure
 S3 illustrates the global morphological variation of theropod femora using
 a NJ tree; Figure S4 highlights the lack of allometric relationship in the
 evolution of a more avian femoral morphology; Table S1 regroups all the
 known CT parameters for CT scanned theropod femora; Table S2 lists all the
 definition for every landmark and semi-landmark used in this study. 2\)
 The excel sheet regroups all parameters linked to the branch length
 sensitivity analyses for our phylogenetically based statistical analyses.
 The first sheet regroups results obtained from the investigation of
 phylogenetic signal given different type of branch length treatment. The
 second sheet regroups all results obtained for allometric investigation
 given different type of branch length treatment. The third sheet regroups
 all the estimated/known time-range for each species featured in this
 study, along a time-calibrated phylogeny. 3\) The document contains a
 review about the different branch length treatment possible, the method we
 used and the results we obtained for our sensitivity analyses along with a
 discussion about how we chose to set branch length for our
 phylogenetically based statistical investigations on fossil taxa in light
 of those different elements.