The evolution of tail joint stiffness in oviraptorosaur dinosaurs and its consequences for tail fucntion

Abstract

Oviraptorosaurs preserve distal tail fronds that are sometimes articulated with a fused pygostyle-like structure. This similarity with birds has led to speculation that they used their tails for display purposes, as in peacocks. The prezygapophyseal morphology and craniocaudally short centra of oviraptorosaur tails indicate a high degree of flexibility per unit of absolute tail length. Their prezygapophyses permitted a large range of motion per joint, which increased tail mobility because the craniocaudally shorter centra allowed the tail to accommodate more joints per unit length. The large muscle volumes reconstructed for oviraptorosaur tails presumably helped to actively stiffen or move them. We predict high passive joint stiffness in their tails because their great depth and breadth created longer moment arms for tissue to leverage its resistance against dorsally/ventrally or laterally directed joint rotation respectively. Shorter tails that evolved via craniocaudally shorter centra also lead to the same prediction because centrum length affects the ...