Fossil Friday – Xena the mammoth’s tusks

“Xena” is the most complete Columbian mammoth specimen recovered from Diamond Valley Lake, including a nearly perfect skull and lots of postcranial material. Both of Xena’s tusks were also recovered, and are on display with the rest of her skeleton at the Western Science Center.

Elephants and their relatives (proboscideans) use their tusks in all kinds of ways, including fighting, stripping vegetation, and digging water holes. While the tusks are modified incisor teeth, they do not have enamel (some extinct lineages did, but that’s another story), so tusks are typically heavily worn at the tips. The polished wear facets are easily visible in the image above.

Another curious feature of proboscideans is that, in most individuals, one of the tusks tends to be more heavily worn that the other. In our mounted cast of Xena, you can see that her left tusk is more heavily worn that the right one, as it’s blunter and somewhat shorter:

Since proboscidean tusks are worn during behavioral activities, it’s possible that the differential tusk wear is evidence for lateralization, or handedness. Most animals show a preference for using one side of their body over the other. This can be expressed in a variety of ways, including a preference for using a particular hand for detailed tasks in humans, or for using one side of the mouth in feeding in whales. For some unknown reason, in almost all species that show lateralization, right-handedness is more common. Modern elephants are also lateralized; an elephant will always tend to curl its trunk in the same direction when pulling up grass, for example. Differential tusk wear suggests that they also show handedness in behaviors that involve the tusks. In Xena’s case, the more heavily worn left tusk suggests that she was left-handed.

We recently produced a cast of Xena’s left tusk, which will be auctioned off at the Western Science Center’s annual Science Under the Stars fundraiser on September 12. If your in Southern California consider coming the the event to support the museum!


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