User:EvilFlyingMonkey/Elephant evolution

Elephants have originated from some common proboscidea-Sirenian ancestor. Their fossils are abundantly  found in Eocene, Miocene beds. Their main stages of evolution happened in Africa. Later they migrated to other and became widespread in North America, South America and Eurasia.

Adaptations

 * 1) increase in mass
 * 2) heavily built pillar like limbs to support heavy body
 * 3) short and broad neck
 * 4) large and heavy head, skull with extensive air cells
 * 5) Proboscis or trunk developed by elongation of upper lip
 * 6) Second pair of incisors of upper jaw modified to tusks.

Ancestry
The phylogeny of elephants represent a polyphyletic ancestory. The first known ancestors of proboscideans as a whole are regarded as Moeritheres, which lived in Egypt during late Eocene period.

Moeritherium
Moeritherium ('the beast from Lake Moeris') is a genus consisting of several species. These prehistoric mammals are related to the elephant and, more distantly, the sea cow. They lived during the Eocene epoch.

The Moeritherium species were pig-like animals that lived about 37-35 million years ago. The Moeritherium resembled modern tapirs or pygmy hippopotamuses. It was smaller than modern elephants, standing only 70 cm high at the shoulder and was about 3 m long.

Phiomia
Phiomia is an extinct [genus]] of basal proboscid that lived during the Late Eocene to Early Oligocene some 36-35 million years ago. Their fossils have been found lower oligocene deposits near lake Moeris in Africa and Siwalik ranges in India. "Phiomia serridens" means "saw-toothed animal of Faiyum". Their limbs were quite similar to modern elephants and skull was large and contained air cells. based on its nasal bones it had a very short trunk.

Deinotherium
Deinotheriums were giganatic reltives of elphants with shorter trunks. They lacked upper tusks but had lower tusks. It was widely present in Euraisa and Africa and last survivors were found in pleistocene deposits in Africa.

Mastodon
Mastodons were elephant like forms that flourished in Africa, Eurasia, America from lower Oligocene to Miocene and even upto upper Pleistocene. They had tusks on both upper and lower jaws. Two lines evolved from paleomastodon, true mastodons and bunomastodons.

True Mastodons
They were of elpehant size and  were found in North America until postglacial time in Pleistocene.

Bunomastodons
Bunomastodons molars ahd additional cusps and folds. Thebunomastodons with complicated molars diversified and evolved into several branches. Gomphotherium and and tetralophodon are some important species evolved from bunomastodons.

Stegomastodon
Stegomastodon ('roof nipple tooth') is an extinct genus of gomphothere, a family of proboscideans. It is not to be confused with the genus Mammut from a different proboscidean family, whose members are commonly called "mastodons", nor with the genus Stegodon, from yet another proboscidean sub-family, whose members are commonly called "stegodonts".

Stegolophodon
Stegolophodons apperead in Miocene and was intermediate in structure between long jawed mastodons and primitive elpehants. They changed their habits of digging from digging to burrowing and started feeding on leaves and grass. So the showel like teeth of bunomastodons with high cusps became gradually shorter. The lower tusks were absent and upper tusks were large.