This specimen, Dinosaur National Monument Specimen 28, when seen in lateral view (upper image) shows significant dorsiflexion. But this an extreme pose with the neck drawn back steeply. It is in what is often referred to as a "death pose", with the neural spines in solid bone-to-bone contact. The neck could not have dorsiflexed further, as apparent in the lower image. Remove this extreme dorsiflexion and bring the neck into a neutral state of flexion, and the neck would have been essentially straight, not giraffe-like.
Copyright © 2011 Kent A. Stevens, University of Oregon