Why does animals of neonatal age has more bones as compared to adult animals?

Neonatal animals have more bones than adults because many of their bones are initially formed as separate pieces of cartilage or ossified structures that later fuse together during growth. For example, the skull of a newborn has several unfused sutures and fontanelles, allowing for flexibility during birth and rapid brain growth. As the animal matures, certain bones, like those in the spine and skull, fuse, resulting in a lower total bone count in adults.