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Elephant Evolution

Zoological Classification

Elephant comes from the Greek word "elephas" meaning ivory. This, of course, refers to their tusks. In scientific nomenclature, elephants belong to the order Proboscidae. This word is also Greek referring to the other distinctive elephant anatomy, the trunk.

In understanding elephant evolution, I think we should first discuss zoological nomenclature. In science, animals and plants are classified and named using a universal system and language. At the narrowest or top level is the genus and species. Every animal and plant can be identified by its two-word (genus and species) name. (i.e. Homo sapiens: man).  When subspecies are present, this can be a three-word name. (i.e. Elephas maximus maximus: Sri Lankan Asian elephant). If you think of species denoting one kind of animal or plant, then genus would include more than one kind. From the top level to the bottom level the number of animals or plants included in each group increases. In general the major categories of classification listed from top to bottom or low to high are:

Keep in mind, between these major levels are usually even further divisions. (i.e. Superfamily or Suborder).

Below is a simple classification of our modern day elephants.

• Kingdom: Animalia
  • Phylum: Chordata
    • Class: Mammalia (mammals)
      • Subclass Eutheria (Placental mammals)
        • Order: Proboscidae
          • Family: Moeritheriidae
            • Genus: Moeritherium
          • Family: Palaeomastodontidae
            • Genus: Palaeomastodon
          • Family: Gomphotheriidae
          • Family: Mammutidae
            • Genus Mammut (mastodons)
          • Family: Elephantidae
            • Genus: Primelephas
            • Genus: Mammuthus (mammoths)
            • Genus: Elephas
              • species: maximus (Asian elephants)
            • Genus: Loxodonta
              • species: cyclotis (African forest elephants)
              • species: africana (African savanna elephants)

Classification problems

One of the major criteria for grouping animals in one classification or another is anatomy (bone and teeth structure). This is so because of their durability. The tusks of elephants evolved from enlarged incisor teeth. Most other tusked mammals formed them from canines. This among other characteristics helps identify the elephant's ancestors and relatives. The discovery of new fossils and the use of new scientific techniques could influence the classification of some species considerably.

Although its not a hard and fast rule, in general, the characteristics that distinguishes one classification from another should be true, as a whole, for all members of and below that classification, extinct and extant (living). These distinguishing characteristics should not be true, as a whole, for members outside or above the classification.

Subclass Eutheria

Among the orders emanating from the subclass Eutheria are three that are closely related scientifically.

Order Hyracoidea:

Modern descendants are the hyraxes. African rodent-like animals the size of rabbits.

Order Sirenia:

Modern descendants are manatees and dugongs (sea cows). Seal-like mammals living entirely in water.

Order Proboscidea:

The order of modern elephants.

Scientists, after studying the anatomical and morphological data, have concluded that these three orders share a common ancestor. Despite the differences in appearance and habitat, today it is agreed that the closest living relatives to modern elephants are the hyraxes and sea cows!

Order Proboscidea

Proboscidea, a Greek word, means having a proboscis, or nose. Over 50 million years, it has been determined that there have been over 350 species of proboscideans. These animals inhabited every continent of the world, except for Antarctica and Australia. Today there are only three major species left; Asian, African savanna, and African forest elephants.

Moeritherium (extinct)

Moeritherium, pronounced mee-ri-THEER-ee-um, is the earliest known member of the order Proboscidea. The first fossils were discovered in 1904 at El Faiyum oasis in Egypt. This oasis was known as Lake Moeris in ancient Egypt Moeritherium fossils showed the beginnings of enlarged incisors (tusks) but there is no evidence of a trunk. They lived about 50 million years ago with a hippo-like lifestyle. In fact, they have been described as pygmy hippopotami. They were about the size of a pig standing 70cm at the shoulders with stout elephantine legs and a long body.

Palaeomastodon (extinct)

Not directly descended from Moeritherium, but farther up the evolutionary tree is the palaeomastodon. (Greek for ancient mastodon) While one might not recognize a Moeritherium as an elephant ancestor, the palaeomastodon would be immediately suspected. The nose is elongated and probably could be described as a small trunk. The incisors are much more enlarged than the moeritherium and there are the beginnings of lower jaw tusk as well. Palaeomastodon, measuring 6.5 ft. at the shoulders, is usually described as the earliest elephant-like proboscidean. They lived from about 30-34 million years ago.

Gomphotheres (extinct)

Gomphotheres includes the most diverse and successful group of proboscideans overall. This is partly because this group had become the catch all classification for elephant ancestors and relatives. There is still some controversy over which species actually belong to this classification. Most gomphotheres were about 6-7 feet tall at the shoulders, but others reached a height of nearly 10 feet. Most gomphotheres had tusks in both upper and lower jaw, while others only possessed the upper jaw tusk. The earliest gomphotheres are believed to have appeared about 20 million years ago and lasted until 1 million years ago.

Mastodons (extinct)

Contrary to popular belief, mastodons are not that closely related to mammoths. Mastodons descended from early gomphotheres and belong to the family Mammutidae. Mammoths belong to the family Elephantidae and evolved farther up the evolutionary tree. Both of these animals were similar in external appearances, however the mastodons were stockier and heavier framed with more of a flattened head than the mammoths. Part of the reason for the confusion is mastodons existed from 20 million years ago to just 10000 years ago, encompassing the period when mammoths roamed the earth. Both inhabiting the same regions.

Primelephas (extinct)

Primelephas is the oldest ancestor in the family Elephantidae. This is the family of our modern living Asian and African species and also the extinct mammoths. It possessed two sets of tusks; upper jaw and lower jaw and lived 7-5 million years ago.

Mammoths (extinct)

From Primelephas, elephant evolution seemed to divide into two branches. One branch evolving into Loxodonta (African elephants) and the other evolving into Elephas (Asian elephants) and Mammuthus (mammoths). Mammoths lived from 2 million years ago to 8000 years ago. They were huge animals standing 10-12 feet high at the shoulders. They had a massive set of tusks and long dense hair suitable for cold climates. Their fossils have been found on all continents except for Australia and South America. Drawings of mammoths have been found in caves, suggesting early man was familiar with this elephant ancestor. Mammoths are probably the best known and best studied of all elephant forebearers because of well preserved, frozen carcasses found in Alaska and Siberia.

Modern elephants

That leads us to the three surviving proboscidean species; Loxodonta africana, Loxodonta cyclotis, and Elephas maximus. All evolved in Africa but the Asian elephant later migrated to Eurasia.

• Genus Loxodonta contains three species:
  • africana africana (Cape elephant)
  • cyclotis (Forest elephant)
  • africana oxyotis (African steppe elephant)

• Genus Elephas contains four species:
  • maximus bengalensis (Indian elephant)
  • maximus hirsutus (Malayan elephant)
  • maximus maximus (Ceylon elephant)
  • maximus sumatranus (Sumatran elephant)

These are all that's left of the diverse and prolific proboscideans.

Conclusion

The Proboscidea order has over 50 million years contained over 350 species. Today only three major species remain. It has been said that the high specialization combined with the continued increase in size and weight, contributed to the demise of a lot of the species. Sudden changes in the environment made it difficult for highly specialized animals to adapt. This coupled with a slow and low reproductive rate could mean disaster to some species.