Deinonychus
The species name antirrhopus means “counter balance”. This refers to Ostrom's idea that the tail balanced the front of the body. As in other dromaeosaurs, the tail vertebrae have ossified (bony) tendons and super-long bone processes. These features seemed to make the tail into a stiff counterbalance. A fossil of the closely related Velociraptor has an connected tail skeleton that is curved side to side in a long S–shape. This suggests that, in life, the tail could swish to the sides with some flexibility.