The evolution of femoral morphology in giant non-avian theropod dinosaurs
Data files
Feb 22, 2024 version files 1.45 MB
Abstract
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.
README: The evolution of femoral morphology in giant non-avian theropod dinosaurs
https://doi.org/10.5061/dryad.tx95x6b52
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.