The Landau Reflex and Symmetrical Tonic Neck Reflex are transitory reflexes; both come up a few months after birth.
The Symmetrical Tonic Neck reflex forms the bridge from belly crawling to crawling on all fours. It makes sure that the baby can come off the ground against gravity. When a baby is on hands and knees, he will lower his butt to his heels as his head bends up backwards while his arms stretch. If he bends his head forward, his legs stretch to 90 degrees and his arms bend so that his head sinks to the floor.