Theropod dinosaurs that rapidly evolved large body size also evolved bony skull ornaments, finds a study published in Nature Communications this week. Large theropods, such as Tyrannosaurus rex, had bony crests or knobs on their heads that may have functioned as signals to potential mates or competitors.
In modern animals, crests, horns and related structures are known to have various functions as ornaments for communication and as weapons. However, dinosaurs also had a wide diversity of similar structures that are currently poorly understood.
Terry Gates and colleagues investigated the relationship between body size and skull ornamentation across the theropod dinosaurs. They observed that the evolution of large body size was accelerated in lineages with bony skull structures, compared to those without such features. However, this relationship was absent for feathered theropod dinosaurs, some of which are known to have had crests made of feathers or other soft tissues instead of bone.
An open habitat may have favoured both large body size and conspicuous features for signalling. However, not enough is known about the ecology of theropods to exclude other explanations for the observed relationship between the evolution of body size and bony skull structures.