The long deep compressed tail was particularly adapted for locomotion in the water.

It may also have served to balance the creature when standing erect on shore.

The broad expanded lip of bone known as the fourth trochanter, on the inner posterior face of the femur or thigh bone was for the attachment of powerful tail muscles similar to those which enable the crocodile to move its tail from side to side with such dexterity.

This trochanter is absent from the thigh bones of land-inhabiting dinosaurs with short tails, such as _Stegosaurus_ and _Triceratops_.

The tail muscles were attached to the vertebrae by numerous rod-like tendons which are preserved in position as fossils on the erect skeleton.