Variants of a mold are catalogued separately, so each one has its own sets and minifigs. Check these too if something you expect is missing here.

• 103472pr0001 Animal Body Part, Dinosaur, Brachiosaurus Neck with Sand Blue Markings Print this part is a pair of it
• 3531 Animal Body Part, Dinosaur, Brachiosaurus Lower Jaw with Teeth [Plain] Pair of this part