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Mammoths.
An imperial mammoth (Mammuthus imperator), marches through an oxbow lake in Southern California 300,000 years ago. (See entire painting.)

FOSSIL FIELD GUIDE

Mammuthus species
Mammoths
Family: Elephantidae

Time
Pleistocene Epoch

Description
Mammoths are extinct proboscideans (pro-bah-SID-ee-inz), a group of mammals that include modern elephants as well as the extinct mastodons and gomphotheres. Mammoths were grazers, feeding mainly on grass and flowering plants. During a 60 to 80-year life span, a mammoth would go through up to six sets of flat molar teeth. The first, or baby teeth, were much smaller than the adult teeth, which were about the size of a large shoe and had a flat, ridged surface adapted for grinding up tough plant material. The largest species of mammoth (Mammuthus imperator) reached 13 feet (3.9 meters); the smallest pygmy mammoths (Mammuthus exilis) grew four to eight feet in height. Compared to mastodons, mammoths had wider heads, a more sloping back, and longer, curved tusks. These tusks were used for protection, to establish dominance, and to help gather food. Paleontologists have found that the inner surface of one tusk tends to be more worn than the other, indicating that mammoths could be "right-tusked" or "left-tusked."


San Diego Natural History Museum catalog no. 27226
Partial lower jaw (left mandible) of a mammoth with a molar and unerupted molar visible on the left. This specimen is from the Middle Pleistocene Bay Point Formation in Point Loma and is approximately 220,000 years old. The fossil measures approximately 15.5 inches (39 cm.)

During the Pleistocene Epoch (1.6 million to 10,000 years ago), mammoths could be found in grassland habitats throughout the northern hemisphere. From their Eurasian homeland they entered North America early in the Pleistocene by way of the Bering land bridge. Paleontologists have learned a great deal about these ancient elephants by studying their bones and teeth. In addition, the discovery of complete frozen mammoths in Siberia have given scientists the extraordinary opportunity to study the actual soft tissues of these extinct animals. And finally, Cro-Magnon humans have left us a kind of prehistoric field guide to mammoths in the dramatic cave paintings found on the walls of some western European dry caves.

Several species of mammoths (genus Mammuthus) lived in southern California during the Pleistocene. The Columbian mammoth (Mammuthus columbi) was large, standing 12 feet (3.7m) tall and weighing as much as 10 tons (9 metric tons). The largest animal ever trapped in the Rancho La Brea asphalt deposits in Los Angeles was a Columbian mammoth. In contrast, the smallest mammoth known from southern California is the Channel Island dwarf mammoth (Mammuthus exilis), which stood only four to eight feet tall. Nearly complete remains of M. exilis have been found on Santa Rosa Island south of Santa Barbara. Skeletal remains of a one million year old southern mammoth, Mammuthus meridionalis, were unearthed in the Borrego Badlands of the Anza-Borrego Desert State Park. Younger deposits in the Park have produced remains of a second species of mammoth, Mammuthus imperator. Mammoth fossils have also been discovered in coastal San Diego County, but these consist of only fragmentary remains that cannot be specifically identified.

No one is sure why mammoths became extinct, but their fossil remains clearly show that they were once a conspicuous part of grassland communities. Perhaps climatic change, or human overhunting, or even disease caused the demise of these mighty beasts.


Text: Kathleen Roll in consultation with Dr. Tom Deméré
Painting: Jim Melli
Photo: Nancy Owens Renner