 However, the atlanto-occipital joint, which controls neck movement, was stronger than it is in other sloths, which was probably an adaptation for bottom feeding to keep the head in a fixed position.Like in whales, the head could align directly with the spine.The spinous process of the first thoracic vertebra is nearly vertical, but, unlike other sloths, the other vertebrae incline towards the tail; inclination increases in later species, with "T. littoralis" and "T. carolomartini" having a 70° inclination as opposed to "T. antiquus" and "T. natans" with a 30° inclination.