How theropod dinosaur skulls experience stress and strain during the application of adductor muscle loads provides a unique insight into their feeding behaviour and principles of skeletal construction and scaling. Of particular interest are unusual cranial morphologies, such as those seen in the spinosaurid theropods, Baryonyx walkeri, Suchomimus tenerensis, Irritator challengeri and Spinosaurus aegyptiacus. This study uses the engineering technique finite element analysis to reconstruct feeding-related stress and strain in the skulls of seven theropod dinosaurs: five non-neotetanurans (Afrovenator, Dubreuillosaurus, Monolophosaurus, Spinosaurus and Suchomimus) and two basal neotetanurans (Acrocanthosaurus and Carcharodontosaurus). Two-dimensional finite element models are created, and simulated adductor muscle loads are applied in proportion to the lateral surface area of the skull, thereby removing the influence of size and testing the efficiency of shape at resisting relative loads. Results show a significant size-related trend, with large taxa experiencing greater stresses than smaller taxa. Whilst Suchomimus scales with other theropods, Spinosaurus is a notable outlier and experiences much higher magnitudes of cranial stress than would be predicted. It may be that when realistic loading parameters are considered, larger theropods mitigate potential cranial weakness through concomitant scaling of adductor muscle and bite force or through modifications to feeding ecology, especially in taxa such as Spinosaurus. Given the 2D nature of these models, results and interpretations should be treated with caution, and are at best considered predictors of biomechanical performance and feeding ecology, to be tested in the future with more appropriate 3D finite element models.