DOI: 10.5061/dryad.4qrfj6qpp
title: Data from: Constraints and adaptations in crocodyliform skull evolution

description: Crocodyliforms display a diverse range of skull morphologies throughout
 their evolutionary history. Extant crocodilians possess platyrostral
 (broad and flat) snouts, thought to be sub-optimal for resisting feeding
 loads due to the conflicting demands of feeding and hydrodynamic
 constraints. In contrast, numerous Mesozoic crocodyliformes possessed
 oreinirostral (dome-shaped) skulls, were terrestrial, and hence free from
 hydrodynamic constraint. This study aims to examine the role of function
 in determining skull shape in crocodyliformes and assesses the difference
 in stress resistance between oreinirostral and platyrostral taxa. We
 hypothesize that in the absence of hydrodynamic constraints, oreinirostral
 taxa have skulls that are better suited for resisting feeding-induced
 loads. Using finite element analysis (FEA), we evaluated biomechanical
 performance in oreinirostral notosuchian taxa Baurusuchus salgadoensis,
 Montealtosuchus arrudacamposi, and Caipirasuchus paulistanus; compared to
 the extant platyrostral Alligator mississippiensis, Crocodylus niloticus,
 and Paleosuchus palpebrosus. Results show that oreinirostral morphologies
 are comparatively better suited for resisting forces generated during
 feeding, with increased muscular efficiency, supporting the hypothesis
 that hydrodynamic constraints influence crocodyliform skull evolution.
description: # Data from: Constraints and adaptations in crocodyliform skull evolution
 Dataset DOI: [10.5061/dryad.4qrfj6qpp](10.5061/dryad.4qrfj6qpp) ##
 Description of the data and file structure ### Files and variables ####
 ### File: ABAQUS_Input_Files.zip **Description:** Abaqus input (.inp)
 files for the following taxa, under the four loading conditions:
 caniniform bilateral biting, molariform bilateral biting, unilateral
 biting, and pull-back loads. 1. *Alligator mississippiensis* 2.
 *Baurusuchus salgadoensis* 3. *Caipirasuchus paulistanus* 4. *Crocodylus
 niloticus* 5. *Montealtosuchus arrudacamposi* 6. *Paleosuchus palpebrosus*
 All files include the mesh geometries, loads (muscle forces), boundary
 conditions necessary to run the FEA. #### File: ABAQUS_RPTs.zip
 **Description:** Field outputs generated from ABAQUs for all six taxa and
 under caniniform unilateral and bilateral biting, molariform biting, and
 pull back loads. All .rpt files were converted to .txt files and formatted
 for use within R for median value calculations. The files contain values
 for von Mises stress (SMises), maximum principal stress (SMax), minimum
 principal stress (SMin), maximum principal strain (EMax), and minimum
 principal strain (EMin). Stress values in MPa, while strain is
 dimensionless.  #### File: Median.R **Description:** An R file containing
 the code for removing the top 5% of the stress/strain values and then
 calculating the bottom 95% of the median stress and strain values from the
 .txt files in the ABAQUS RPTs folder.  #### File:
 Baurusuchus_salgadoensis_(MPMA-62-0001_02).zip **Description:** Specimen:
 *Baurusuchus salgadoensis* (MPMA-62-0001/02). Scanned using Siemens
 Somatom Spirit scanner, at Unidade de Radiológica Dr. Fabrício Mallouk,
 Monte Alto SP, Brazil. The original DICOM dataset and relabeled TIFFs are
 included as separate folders, with a voxel size of 0.625 x 0.625 x 0.8 mm.
 #### File: Caipirasuchus_paulistanus_(MPMA-67-0001_00).zip
 **Description:** Specimen: *Caipirasuchus paulistanus* (MPMA-67-0001/00).
 Scanned using Siemens Somatom Spirit scanner at Hospital das Clínicas da
 Universidade Federal do Triangulo Mineiro, Brazil. The original DICOM
 dataset and re-oriented TIFFs are included as separate folders, with a
 voxel size of 0.429 x 0.429 x 0.3 mm.  #### File:
 Paleosuchus_palpebrosus_(OUNHM_1451).zip **Description:** Specimen:
 *Paleosuchus palpebrosus* (OUNHM 1451), common name - Cuvier's dwarf
 caiman. Scanned using Nikon XTH225ST at the University of Bristol. The
 original uncompressed microCT TIFF stack is included with the scan
 parameters, with a voxel size of 0.099 x 0.099 x 0.099 mm.  #### File:
 Montealtosuchus_arrudacamposi_(MPMA-16-0007_04).zip
 **Description:** Specimen: *Montealtosuchus
 arrudacamposi* (MPMA-16-0007/04). Scanned using Discovery CT750 HD scanner
 at Instituto de Radiologia – Faculdade de Medicina de São Paulo, USP,
 Brazil. The complete DICOM dataset is included as separate folders, with a
 voxel size of 0.63 x 0.63 x 0.63 mm.  #### File:
 Crocodylus_niloticus_(OUNHM_23306).zip **Description:** Specimen:
 *Crocodylus niloticus* (OUNHM 23306), common name - Nile crocodile.
 Scanned using Nikon XTH225ST at the University of Bristol. The original
 uncompressed microCT TIFF stack is included with the scan info and
 parameters, with a voxel size of 0.12 x 0.12 x 0.25.  #### File:
 Croc_muscle_forces.xlsx **Description:** This file contains two
 spreadsheets including muscle force calculations for *Baurusuchus* and
 subsequent calculations and scaling for all other taxa. Models were not
 scaled to the same size, and forces were scaled to surface area instead.
 1. **Bauru muscle calculations:** This sheet contains the measurements for
 the left half of the cranial adductor muscles of *Baurusuchus*, obtained
 from digital muscle reconstructions. The columns in this sheet represent:
 * Muscle Name – Abbreviation for individual muscles (e.g., mAMEM, mAMES).
 * Volume (mm^3^) – Measured muscle volumes. * Muscle Length (mm) –
 Estimated total muscle length. * Fibre Length (mm) – Estimated muscle
 fiber length, using the assumption that fiber lengths are 1/3^rd^ of the
 muscle length. * PCSA (ML = FL) – Estimated physiological cross sectional
 area (in mm^2^), obtained by dividing muscle volume by muscle lengths *
 PCSA (ML = FL/3) – Estimated physiological cross sectional area (in
 mm^2^), obtained by dividing muscle volume by fiber lengths, fiber lengths
 are 1/3^rd^ of the muscle length. * Muscle Stress – Assumed muscle stress
 value. * Muscle Force (ML = FL) – Calculated muscle forces derived from
 multiplying PCSA (ML = FL) and muscle stress. * Muscle Force (ML = FL/3) –
 Calculated muscle forces derived from multiplying PCSA (ML = FL/3) and
 muscle stress. 2. **Muscle Forces:** This sheet aggregates and scales
 muscle force data obtained from *Baurusuchus* for comparative modeling for
 all six taxa in the study. The columns in this sheet include: * Taxon –
 Species (e.g., *Baurusuchus salgodoensis, Alligator mississippiensis*). *
 TSA (mm^2^) – Total skull surface area * Muscle name – Abbreviation for
 individual muscles (e.g., mAMEM, mAMES). * Ratio of Surface Areas –
 Surface area proportions for each taxon relative to *Baurusuchus* * PCSA
 (mm^2^) left side – Calculated PCSA (per side and total skull). * %
 occupied – Proportion of total skull area occupied by the muscle. * Muscle
 Stress – Assumed muscle stress value. * Force (N) – Calculated muscle
 force (per side and total skull). * No. of nodes – Number of nodes
 selected for each muscle group in ABAQUS. * Force per node – Calculated
 forces divided per node for each muscle group by taxa. #### File:
 3D_FE_Results_USDZ_(iOS_Mac).zip **Description:** 3D FEA results for von
 Mises stress (SMises), maximum principal stress (SMax), minimum principal
 stress (SMin), and minimum principal strain (EMin), for all four loading
 conditions. Exported from ABAQUS as .wrl files, and converted to .usdz
 files which can be viewed without any special software using Quicklook or
 Preview in 3D/AR on iOS and Mac devices.  #### File:
 3D_FE_Results_GLTF_(Windows_Android).zip **Description:** 3D FEA results
 for von Mises stress (SMises), maximum principal stress (SMax), minimum
 principal stress (SMin), and minimum principal strain (EMin) for all four
 loading conditions. Exported from ABAQUS as .wrl files, and converted to
 .gtlf files. Can be viewed without any special software using Windows 3D
 Viewer on Windows or on Android devices, including browsers. iOS/Mac users
 can use Khronos glTF Viewer. #### File: 3D_FE_WRLs_larger_models.zip
 **Description:** 3D FEA results for von Mises stress (SMises), maximum
 principal stress (SMax), minimum principal stress (SMin), and minimum
 principal strain (EMin), for all four loading conditions. These files are
 larger than 100 MB, for *Baurusuchus* and *Crocodylus* and were unable to
 be converted to USDZ/GLTF. Can be viewed using Meshlab, Blender or similar
 CAD programs. Exported directly from ABAQUS.