Fossil of the month: Mammoth tooth
This specimen is a fossil mammoth molar or cheek tooth. It might not look like a tooth, but it is. Mammoths (Mammuthus columbi) were a type of ice age (Pleistocene Epoch) elephant. They are sometimes called wooly mammoths, because preserved specimens with long hair have been found in permafrost in Siberia. Mammoths once lived across much of North America and northern Asia. This specimen was found in Boone County by Winney Dooley and donated to the Kentucky Geological Survey for her children. (See pg. 4 of this KGS newsletter.) The tooth is on display at the Kentucky Geological Survey, where it is enjoyed by the public. The tooth may have been eroded from deposits at Big Bone Lick, a state park in Kentucky, and washed downstream. Pleistocene layers containing similar fossils at Big Bone Lick and other ice age deposits in the Ohio River Valley are 10,000 to 12,000 years old.
Description. Mammoths are a type of ancient elephant. While most ancient organisms have to be reconstructed from only their bones, whole mammoths have been found frozen in permafrost in the Arctic. Hence, scientists know quite a lot about these ancient creatures. Mammoths were similar in appearance to elephants, but taller and more massive. Like modern elephants, they had trunks. They also had long curving tusks, as much as 11.4 ft (3.5 m) long! Their front legs were taller than their back legs so their backs sloped downward from the shoulders (e.g., Haynes, 1991). A full-grown adult male mammoth in Kentucky and surrounding states, would have averaged 12.3 ft (3.75 m) height at the shoulder, which is slightly taller than a modern African elephant (the largest modern elephant). Male mammoths are estimated to have weighed 10.5 tons (9.5 metric tonnes), on average, which is much heavier than the 6.6 ton (6 metric tonnes) average for a modern male African elephant (Larramendi, 2015).
Mammoths vs. Mastodons. Mammoths (Mammuthus) and mastodons (Mammut) are two types of ice age elephants that lived in what is now Kentucky. Genetic studies from fossils show mammoths, mastodons, and modern elephants are different branches of the elephant lineage (Palkopoulou and others, 2018). Mammoths and mastodons are sometimes confused with each other. This is not surprising, since many bones of the two elephants are similar, and the latin name for what we call mastodons (Mammut) sounds like “mammoth.” In general, adult mammoths were taller and longer than adult mastodons. Adult mammoths also had longer tusks than adult mastodons. There is considerable overlap, however, between the sizes of the two. Variation in sizes occurs because of differences between males and females and between juveniles and adults. A real distinction between mammoths and mastodons, regardless of age or sex, is the differences in their molar or cheek teeth (like our fossil of the month). Mammoth molars had broad, thin crowns with small linear ridges, somewhat like a giant file. In contrast, the crowns on mastodon molars had high cones with cusps (e.g., Haynes, 1993).
Range. The oldest mammoths are from the Pliocene Epoch, Neogene Period, 5.5 to 3.5 million years ago, in southern and eastern Africa (e.g., Maglio, 1973). Mammoths came to North America in a series of migrations across a land bridge that existed across the Bering Straits between Alaska and Russia during the Pleistocene Ice Ages (Haynes, 1991; Shoshani, 1998; Debruyne and others, 2008; Lister and Scher, 2015). The oldest mammoths in North America are from the mid-Pleistocene Epoch, 1.4 to 1.5 million years old (Lindsay and others, 1975; Lister and Scher, 2015; MacFadden and Hulbert, 2017). Columbian mammoths in Ohio and Kentucky are from the latest Pleistocene to early Holocene, mostly 25,000 to 11,000 years old (e.g., Tankersley and others, 2015). Columbian mammoths went extinct in the early Holocene, between 11,000 and 10,000 years ago (e.g., Haynes, 1993). Some Wooly mammoths survived on a small Arctic island in Siberia until 4,000 years ago (Vartanyan and others, 2008).
Mammoth and mastodon teeth have been found at several localities in Kentucky including Blue Licks and Big Bone Lick (Cooper, 1931; Jillson, 1936; Schultz and others, 1963). Big Bone Lick has been called the birthplace of North American paleontology because it was the site of the first purposeful excavation for finding and preserving fossil remains in North America. Both Benjamin Franklin and Thomas Jefferson studied fossil bones from Big Bone Lick. Georges Cuvier used mastodon bones from Big Bone Lick, and mammoth, and other fossil bones from other areas, to develop the first scientific evidence for extinction. Ice age bones from Big Bone Lick are in many of the world’s most famous natural history museums. More locally, mammoth and mastodon bones from Big Bone Lick are on public display at the state park, the Cincinnati Natural History Museum, and the Kentucky Geological Survey and Department of Earth and Environmental Sciences at the University of Kentucky. Mammoth and mastodon teeth have been found in other parts of Kentucky, mostly in areas along or draining into the Ohio River.
Learn more about:
- Big Bone Lick
- Benjamin Franklin and mastodon teeth
- Thomas Jefferson, and big mammoth and mastodon bones
- Georges Cuvier and the idea of extinction
What fossil teeth tell us about the way mammoths lived. You have probably heard the saying, “you are what you eat.” This is true for animals living today as well as for ancient animals. Animal teeth are tools which allow food to be processed in the mouth. Fossil teeth, like this month’s fossil, provide information about the animal they came from by (1) their shape, (2) the amount of wear and abrasion, and (3) their isotopic composition.
The shape of teeth allow different types of functions, such as slicing, stabbing, tearing, and grinding. By comparing the shape of fossil teeth to the teeth of animals that live today scientists can interpret if an ancient animal was a meat eater (carnivore), plant eater (herbivore), or both (omnivore). Mammoths have teeth composed of amalgamated plates. They have a broad ridged surface, similar to, but different than modern elephants. These types of teeth are good at grinding food. From the shape of the teeth, paleontologists have long interpreted mammoths as herbivore grazers that ground plants between their molar teeth (Skeels, 1962; Maglio, 1963; Haynes, 1993).
Different types of plants also have different hardness. A lifetime of eating hard or abrasive plants causes different patterns of tooth wear and microwear than a diet of soft plant tissues. Grass, for example, is very abrasive and causes significant wear. Many mammoth teeth show patterns of wear suggestive of a grass-dominant diet (Saarinen and others, 2015), although microwear patterns from mammoth teeth in different areas show they had browsing and mixed feeding habits as well (Rivals and others, 2012).
Different types of plants are composed of different chains of carbon molecules. If a plant-eating animal has a diet dominated by a certain kind of plant, that plant’s composition can leave an imprint in the tooth, which can be detected through isotopic analyses. Isotopic studies of fossil mammoth teeth confirm a dominantly grass diet in many areas, but also show a mixed plant diet in others (Smith and DeSantis, 2018).
Because Ice Age mammoths are also found frozen in permafrost, scientists have actual stomach and intestinal contents to interpret mammoth diets. Stomach and intestinal contents from frozen mammoths include grasses, but also willow and other plant remains (van Geel and others, 2008, 2011). All of the frozen mammoth carcasses are Wooly mammoths. Wooly mammoths are the species of mammoth most people think of when they think of mammoths. These were elephants covered in thick coats of hair, adapted for living in cold, steppe and tundra environments of the Ice Age (e.g., Haynes, 1993). Columbian mammoths were more common in Kentucky.
Columbian mammoths had similar-shaped teeth to their Arctic cousins, but appear to have lived in more temperate climates than Wooly Mammoths (with some overlap of their ranges). Columbian mammoths likely lived in herds in vast prairies south of continental ice sheets, where they could eat prairie grasses, but also a variety of shrubs and herbaceous vegetation. At Big Bone Lick, Kentucky, mammoths occasionally came to the salt lick. They shared a lakeside environment with mastodons, bison, woodland musk ox, stag moose, complex-toothed horse, giant sloths, and deer (Schultz and others, 1963; Tankersley and others, 2015).
Mammoth extinction. Mammoths went extinct 11,000 to 10,000 years ago, except for isolated populations on Siberian islands. Mammoth, mastodon, and many other Ice Age large animals are considered to have gone extinct because of (1) hunting from paleohumans, called the “Pleistocene overkill hypothesis” (Martin, 1984; Fisher, 1987; Meltzer, 2015); (2) climate and subsequent vegetation changes following the last glacial advance (Guthrie, 1984; Graham and others, 1996; Yansa and Adams, 2012; Cooper and others, 2015); or combinations of the two. The loss of so many species of large mammals, is considered by many scientists to be a sixth mass extinction, sometimes called the Holocene extinction, or Anthropocene extinction (Leakey and Lewin, 1995; Ceballos and Ehrlich, 2018; Turvey and Crees, 2019).
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Text and illustrations by Stephen Greb (KGS).