The best known succulents are cacti (family: Cactaceae). Virtually all cacti are succulents, but not all succulents are cacti. There is a significant difference between succulents that evolved in Africa and those that evolved in the Americas, the New World plants called cacti all have spines. No succulent plants arising in the Old World have spines although, through parallel evolution, there are similar species in the Old World that closely resemble species in the new world that do have spines. The functional nature of the shapes evolved independently in each hemisphere, even though the specific structures may differ.