Jaw biomechanics of Troodontidae and their implications for the palaeobiology of this lineage of bird-like theropod dinosaurs

Troodontids are small-bodied paravian theropod dinosaurs that are conspicuous for their close evolutionary relationship with modern birds and unique bauplan among Mesozoic non-avian theropods, part of which has been interpreted as suggestive of a distinctive ecological niche as highly cursorial predators who primarily hunted small prey items or of an increased portion of plant material in their diet compared to other theropods. Despite the increased interest in paleobiology of bird-like dinosaurs more recently, however, feeding biomechanics of troodontids remains largely uninvestigated. Here, the feeding and predatory behaviours of five troodontids are investigated, using beam theory on their mandibles. Mandibular strength profiles reveal that the anterior extremity of the jaws in troodontids, even in early-diverging forms, is better adapted to endure mediolateral and torsional loads compared to most other theropods such as dromaeosaurids. In later-diverging, relatively large-bodied taxa, the anterior half of the dentary is strengthened in terms of its mediolateral bending rigidity. Such unique profiles suggest the anterior part of the lower jaw played an important role in the life habits of troodontids. These results could be interpreted that the anterior region of the troodontid dentary was used to crop off plant material, or assisted in prey capture when the prey was subdued by the pes of an animal.