EARLY ELEPHANTS
Modern elephants (proboscideans) have two tusks
emerging from their upper jaw. Some fossil proboscideans had four tusks -
a pair from the upper jaw and a pair from the lower jaw (mandible). A
couple examples are shown below - Amebelodon and Gomphotherium.
Amebelodon is one of these odd, four-tusked fossil elephants. Its lower
tusks were nestled against each other and were dorso-ventrally flattened,
forming a shovel-like structure. Like other proboscideans, Amebelodon
was herbivorous. Its “shovel” has been inferred to have aided the animal
in scooping up lacustrine vegetation, removing tree bark, and other
activities. The body size of various species of Amebelodon seems
to have ranged from being larger than to smaller than living elephant species.
Amebelodon remains have been found in the Upper Miocene of North America, eastern
Asia, and northern Africa. These fossil occurrences date from about 5 to
9 million years.
Classification: Animalia, Chordata, Vertebrata, Mammalia, Proboscidea,
Euelephantoidea, Gomphotheriidae
Amebelodon lower jaw from the Upper Miocene of Florida, USA. A
pair of tusks originally protruded from the large opening at front (see
reconstructions below). (UF 217472, Florida Museum of Natural History,
University of Florida, Gainesville, Florida, USA)
Amebelodon skull drawing showing position of lower jaw.
Amebelodon reconstruction (painting by Velizar Simeonovski).
Gomphotherium is another early proboscidean. It also had four tusks - one pair
from the upper jaw and one pair from the lower jaw. Its body size was
about the same as the living Asian elephant (Elephas
maximus). Tooth morphology and tooth isotopic composition studies
indicate that Gomphotherium was herbivorous, primarily a browser (leaf
eater) in woodland facies.
Gomphotherium remains are widespread - they have been found in the Miocene of North
America, Eurasia, and Africa, plus the Lower Pliocene of North America and
Europe.
Classification: Animalia, Chordata, Vertebrata, Mammalia,
Proboscidea, Euelephantoidea, Gomphotheriidae
Gomphotherium productum (Cope, 1874) partial lower jaw from the Miocene of
Oklahoma, USA (OMNH 4259, Oklahoma Museum of Natural History, University of
Oklahoma, Norman, Oklahoma, USA).
Gomphotherium productum (Cope, 1874) upper tusk from the Miocene of Oklahoma,
USA (OMNH 4273, Oklahoma Museum of Natural History, University of Oklahoma,
Norman, Oklahoma, USA).
Gomphotherium productum skull drawing showing position of lower jaw and upper
tusk.
Gomphotherium productum reconstruction (painting by Velizar Simeonovski).