Jaw morphology is closely linked to both diet and biomechanical performance, and jaws are one of the most common Mesozoic mammal fossil elements. Knowledge of the dietary and functional diversity of early mammals informs on the ecological structure of palaeocommunities throughout the longest era of mammalian evolution: the Mesozoic. Here, we analyse how jaw shape and mechanical advantage of the masseter (MAM) and temporalis (MAT) muscles relate to diet in 70 extant and 45 extinct mammals spanning the Late Triassic-Late Cretaceous. In extant mammals, jaw shape discriminates well between dietary groups: insectivores have long jaws, carnivores intermediate to short jaws, and herbivores have short jaws. Insectivores have low MAM and MAT, carnivores have low MAM and high MAT, and herbivores have high MAM and MAT. These traits are also informative of diet among Mesozoic mammals (based on previous independent determinations of diet) and set the basis for future ecomorphological studies.

颌骨形态与饮食和生物力学性能密切相关，颌骨是最常见的中生代哺乳动物化石元素之一。了解早期哺乳动物的饮食和功能多样性可以了解哺乳动物进化最长时期（中生代）中古群落的生态结构。在这里，我们分析了三叠纪晚期至白垩纪晚期的 70 种现存哺乳动物和 45 种已灭绝哺乳动物的颌骨形状和咬肌 (MAM) 和颞肌 (MAT) 肌肉的机械优势如何与饮食相关。在现存的哺乳动物中，颌骨形状可以很好地区分饮食组：食虫动物的颌骨长，食肉动物的颌骨短，食草动物的颌骨短。食虫动物具有低 MAM 和 MAT，食肉动物具有低 MAM 和高 MAT，食草动物具有高 MAM 和 MAT。