Final answer:
The anterior and posterior sacroiliac ligaments are primarily responsible for preventing the anterior movement of the sacral base, with additional support provided by the sacrospinous and sacrotuberous ligaments.
Step-by-step explanation:
The ligaments that prevent the sacral base from moving anteriorly are the anterior sacroiliac ligament and posterior sacroiliac ligament. These ligaments support the largely immobile sacroiliac joint, which is the connection between the sacrum and ilium parts of the hip bone. In addition to these, the sacrospinous ligament and sacrotuberous ligament also span the sacrum and hip bone, aiding in the immobilization and support of the sacrum as it bears the body's weight.