A morphometric approach to the specific separation of the humeri and femora of Dicraeosaurus from the Late Jurassic of Tendaguru,Tanzania

Abstract

The two species of dicraeosaurid dinosaurs Dicraeosaurus, Dicraeosaurus hansemanni, and Dicraeosaurus sattleri, have been distinguished mainly by their differences in size and geological age, as they occur in different members of the Late Jurassic Tendaguru Formation of Tanzania. Linear and geometric morphometric measurements distinguish between the humeri and femora of both species. Linear measurements and Principal Component Analysis of Thin-plate Splines reveal strong differences in size and shape between their humeri and weak differences between their femora, also supported by a Discriminant Factor Analysis. Generally, the humerus and femur of D. hansemanni are slightly longer and more robust than those of D. sattleri. Further, the humerus is shorter in relation to the femur in D. sattleri, related to its more distally positioned deltopectoral crest, resulting in differences in its arc of movement and mechanical power. Thus, a morphological separation between the humeri and femora of D. hansemanni fro...