 The vertebral centra segments progressively became shorter in length, making the spine more stable, probably an adaptation for digging efficiency.In later species, the spinous processes which jut upwards from the vertebrae are markedly taller in the thoracic vertebrae than the neck vertebrae, as opposed to other sloths where they are around the same height.The small neck vertebrae show they had weak neck muscles, as an aquatic creature does not need to hold its head up, and the neck probably faced downwards while at rest.