Mesozoic crurotarsans exhibited diverse morphologies and feeding modes, representing considerable ecological diversity, yet macroevolutionary patterns remain unexplored. Here we employ a unique combination of morphological and biomechanical disparity metrics to quantify the ecological diversity and trophic radiations of Mesozoic crurotarsans, using the mandible as a morpho-functional proxy. We recover three major trends. First, the diverse assemblage of Late Triassic crurotarsans was morphologically and biomechanically disparate, implying high levels of ecological variation; but, following the end-Triassic extinction, disparity declined. Second, the Jurassic radiation of marine thalattosuchians resulted in very low morphological disparity but moderate variation in jaw biomechanics, highlighting a hydrodynamic constraint on mandibular form. Third, during the Cretaceous terrestrial radiations of neosuchians and notosuchians, mandibular morphological variation increased considerably. By the Late Cretaceous, crocodylomorphs evolved a range of morphologies equaling Late Triassic crurotarsans. In contrast, biomechanical disparity in the Cretaceous did not increase, essentially decoupling from morphology. This enigmatic result could be attributed to biomechanical evolution in other anatomical regions (e.g. cranium, dentition or postcranium), possibly releasing the mandible from selective pressures. Overall, our analyses reveal a complex relationship between morphological and biomechanical disparity in Mesozoic crurotarsans that culminated in specialized feeding ecologies and associated lifestyles.
Stubbs et al. Morphological analysis - Raw Landmark Data
This is a tps. file containing 2-D digitized landmarks for the mandibles (lower jaws) of 107 Mesozoic crurotarsans, in lateral view. The file describes the landmark coordinates for all 74 landmark points taken on each specimen. Together with the associated NTS. sliders file this is used to compute aligned, Procrustes transformed, coordinates. The file can be read by notepad, PAST and a number of geometric morphometrics software packages, including tps software, MorphoJ, or IMP software.
Stubbs et al. Morphological analysis - Semi-Landmark Data (sliders file)
This simple NTS. file describes which of the 74 landmarks used in this study are sliding (semi-landmarks). The file is required to compute aligned, Procrustes transformed, coordinates; together with the associated raw landmark data file. The file was created in TPSUTIL. To create aligned coordinates both this file and the raw landmark data should be input in TPSRELW using the chord – min d2 sliding method.
Stubbs et al. Morphological analysis - Procrustes Aligned Coordinates
This data file contains the Procrustes transformed aligned 2-D landmark coordinates for 107 Mesozoic crurotarsan mandibles. The file contains taxonomic labels in the first column. The file can be opened in PAST (Palaeontological Statistics). Using the PCA function on all the data will produce a 2-D lateral lower jaw morphospace for Mesozoic crurotarsans.
Stubbs et al. Morphological analysis - PCA axes 1-15
File contains 15 PC scores from the principal component analysis on the Procrustes transformed aligned landmarks. Plotting axes 1 and 2 as an XY plot produces a 2-D lateral mandibular morphospace for Mesozoic crurotarsans. In our main analyses the first 10 axes were used to calculate morphological disparity, together with binary occurrence and groups files using the MDA add-on for MATLAB. Data regarding the stratigraphic occurrences and groupings for each taxon can be found in the electronic supplementary material accompanying our article (Table S1).
Stubbs et al. Biomechanical analysis - Raw biomehanical character data
This file contains the raw data from 14 biomechanical measurements, taken from the mandibles of 107 Mesozoic crurotarsans. To produce a biomechanical morphospace the data should be z-transformed and entered into PAST. Using the PCO (principle coordinates) function and the Gower similarity index will produce a biomechanical mandibular morphospace. Abbreviations for characters: Total mandibular length (TOTL), Quadrate/articular offset (QUADOFF), Relative length of the mandibular symphysis (SYMPH), Relative length of dental row (%DENT), Relative area of the fenestrae (%FEN), Anterior mechanical advantage (AMA), Posterior Mechanical Advantage (PMA), Opening mechanical advantage (OMA), Maximum Second Moment of Area (MAXI), Average Second Moment of Area (AVRI), Max polar moment of inertia (MAXJ), Average polar moment of inertia (AVRJ), Slenderness of the largest tooth (CUSPMAX), The curvature of largest tooth (CURVEMAX). Full descriptions of each character can be found in the electronic supplementary material accompanying the main article.
Stubbs et al. Biomechanical analysis - PCO axes 1-15
File contains 15 PC scores from a principal coordinates analysis of the z-transformed biomechanical data, from 107 Mesozoic crurotarsan mandibles. Plotting axes 1 and 2 as an XY plot produces a biomechanical mandibular morphospace. In our main analyses the first 10 axes were used to calculate biomechanical disparity, together with binary occurrence and groups files using the MDA add-on for MATLAB. Data regarding the stratigraphic occurrences and groupings for each taxon can be found in the electronic supplementary material accompanying our article (Table S1).
