2.Cete (whales and dolphins)
3.Phenacodonta (horses, tapirs and rhinos)
4.Meridungulata (an extinct species)
5.Paenungulata (superorder – elephant ancestors)
It is thought that the modern-day elephant evolved from an aquatic animal that used its trunk as a sort of snorkel while it spent extended periods of time beneath the surface of the water. Even today, elephants are able to swim in this way, staying underwater for hours at a time, with only the tip of their trunk exposed. According to these theories, elephants (Proboscidea) are closely related to manatees and dugong (Sirenia). It is deduced, then, that Proboscidea and Sirenia must share a common ancestor, from which each developed into different species. The Paenungulata group has been identified as the elephant ancestor by intensive DNA research, which revealed that the hyraxes branch off earlier, while the Proboscidea and Sirenia are still closely related in Tethytheria.
“Proboscidea” is a Greek word that means “having a nose”. Over 350 Proboscidea have been identified as having existed over the last 50 million years. The only areas that were not found to have been home at least some of these species are Antarctica and Australia. All but 3 of these species are now extinct, leaving only the Asian Elephant, African Savanna Elephant (the world’s largest land mammal) and African Forest Elephant. Many of the more delicate and specialised species are likely to have died due to environmental changes that, when coupled with slow reproductive rates, spelt extinction.
The African species can be found in nearly 40 African countries. They are larger than their Asian counterparts. They are further distinguished by different ear- and head shapes. Originally, the two different African elephants were considered to be subspecies. However, DNA research has revealed that they are actually two separate species. This classification has important ramifications in terms of conservation and the population statistics.
Research continues in an effort to bridge the gaps that exist in the evolutionary development of these extraordinary animals. There remain mysteries regarding associated species and the exact path these ancestors followed before evolving into the elephant as we know it today.
Here is more about Elephant Evolution