Figure 2: Model support for pterosaur body size evolution.
From: Competition and constraint drove Cope's rule in the evolution of giant flying reptiles
AICc weights are shown for (a) models in which the root node value (Z0) is equal to the macroevolutionary optimum for basal (non-pterodactyloid) pterosaurs (θ). (b) Models in which the root node value is estimated separately from the macroevolutionary optimum for basal pterosaurs. *indicates models with median AICc weights above an arbitrarily-specified value of 0.05. Results from the following models are shown: OUM is an Ornstein–Uhlenbeck model with group-specific trait optima (θ); OUMV allows a group-specific θ and stochastic rate parameter (β, Brownian variance); OUMA allows group-specific θ and attraction parameters (α). Model name suffixes indicate the number of groups specified with distinct macroevolutionary regimes: 2, basal (non-pterodactyloids) and Pterodactyloidea; 3, basal, Archaeopterodactyloidea and Ornithocheiroidea; 4, basal, Archaeopterodactyloidea, Pteranodontoidea and Azhdarchoidea; time 1, Triassic–Kimmeridgian and Tithonian–Cretaceous; time 2, Triassic–Tithonian and Cretaceous. Thick lines indicate median values across 25 time-calibrated phylogenies, boxes indicate interquartile ranges, whiskers indicate ranges excluding outliers, and circles indicate outliers. Dashed line occurs at 0.05, non-dashed, horizontal line occurs at 0.025.
