Complex sentence: The exterior surface is crowded with spines that may be up to long; initially white and becoming dark brown in maturity, the spines are often joined at the tips in groups of 3 or 4.
Split into simpler sentences: The exterior surface is crowded with spines that may be up to long. Initially white and becoming dark brown in maturity, the spines are often joined at the tips in groups of 3 or 4.