The American Mastodon (Mammut americanum) was a massive, extinct relative of the modern elephant that roamed North America for millions of years, disappearing around 11,000 years ago. Although contemporaries of the Woolly Mammoth, mastodons belonged to a separate evolutionary branch, diverging from the ancestors of modern elephants about 25 million years ago. The most commonly found fossils of this ancient mammal are its teeth, which hold the key to understanding the animal’s lifestyle and diet. These unique molars provide scientists with a wealth of information about the species’ place in the Pleistocene ecosystem.
The Unique Anatomy of the Mastodon Molar
The most striking feature of the mastodon molar is its distinct chewing surface, which appears mountainous or nobby. The molars are characterized by a series of high, cone-shaped cusps. These cusps are arranged in parallel pairs, forming transverse ridges, or lophs, across the width of the tooth.
This specific arrangement gives the tooth a “zygodont” morphology, meaning the cusps are connected into sharp ridges. The number of these lophs varies depending on the tooth’s position, with the largest molars typically featuring four to five distinct ridges. The name “mastodon” itself translates literally to “breast tooth,” a direct reference to the nipple-like shape of these high cusps.
The main body of the molar is composed of dentin, covered by a thick layer of enamel, which forms the sharp, durable chewing ridges. As is common for proboscideans, mastodons had a limited number of molars erupting and wearing down over their lifespan. However, the enamel on the molars forms a band around the crown, which differs from the complex internal enamel structure seen in the teeth of mammoths and modern elephants.
How Tooth Structure Reveals Diet
The specialized anatomy of the mastodon molar is a direct adaptation to its preferred diet as a browser. The high, sharp cusps and ridges were suited for crushing and shearing tough, woody vegetation, allowing the mastodon to effectively process the leaves, twigs, and bark it consumed.
When the mastodon chewed, the upper and lower molars acted like a mortar and pestle or a set of heavy-duty shears, rather than a grinding stone. This crushing motion was necessary to break down the coarse, fibrous material found in forest environments. Studies of dental wear patterns and preserved stomach contents confirm that the animals primarily fed on woody forest vegetation, including conifer twigs, shrubs, and leaves.
While traditionally considered strict browsers, recent studies of ancient dental calculus—hardened plaque on the teeth—suggest mastodons may have occasionally incorporated grasses into their diet. This mixed feeding likely occurred in areas where woody browse was less available, demonstrating flexibility in their foraging habits. However, the fundamental design of the tooth remained optimized for crushing the tougher materials of a browsing diet.
Mastodon Versus Mammoth Teeth
The difference in tooth structure between the mastodon and its contemporary, the Woolly Mammoth (Mammuthus primigenius), reflects their separate dietary niches and habitats. Mastodons possessed the high, pointed, crushing teeth of a browser, while mammoths evolved flat, ridged teeth built for grinding.
A mammoth molar resembles a large, rectangular box with a flat, washboard-like chewing surface. This flat surface is made up of numerous thin, parallel plates of enamel, known as lamellae, cemented together. As the tooth wore down, these enamel plates created rough, abrasive ridges, functioning like a giant file.
This grinding mechanism was adapted for a grazing diet, enabling the mammoth to efficiently pulverize the tough, silica-rich grasses of the open steppe environment. Conversely, the mastodon’s cusped teeth would have been ineffective at grinding, just as the mammoth’s flat teeth would have struggled to shear woody branches. The distinct dental morphology serves as a record of two different megafauna occupying two distinct ecological roles: the mastodon in forests and the mammoth on grasslands.