We present the first report on the use of the non-invasive method of synchrotron X-ray microtomography to model the dynamics and theoretical bite forces of arthropod mouthparts. The nature of the data allowed us to include precise measurements of muscle areas and the spatial geometry of muscle origins and insertions into a biomechanical model of a morphological microstructure. We investigated the functional morphology of the chelicera in the oribatid mite Archegozetes longisetosus (Acari, Oribatida), a model organism for Chelicerata. The chelicera represents a first-class lever; the intrinsic muscular system consists of a feather-shaped depressor with six muscle bundles and a bouquet-shaped levator with 16 bundles. The relative bite forces, as compared with body mass (force/mass^2/3), are 390 N kg^–1 and lie within those known for vertebrates (≤260 N kg^–1) and decapod chelae (≤915 N kg^–1). The dynamics of force transmission and bite forces during the movement of the apotele are calculated. The conserved organization of cheliceral musculature allows broad adaptation of the model to other chelicerate taxa.