The Most Surprising Thing Found in the Library

Some months back, we were doing some spring cleaning in the Library’s Lower Level. There’s a room there that was designed for materials processing, a fancy way of describing the “holding pen” for new materials waiting to be added to the collection. While tidying up, we opened a drawer and discovered a small cardboard box. Inside the box was the most startling piece of our collection we’ve ever encountered.

The box contained four prehistoric horse teeth.

Eohippus tooth, Eocene Epoch. Worland, WY. Gift of Ellen B. Wells.
Eohippus tooth, Eocene Epoch. Worland, WY. Gift of Ellen B. Wells.

It’s a little ambiguous to call these “horse” teeth, as the genera involved here definitely pre-date the horse as we know it. The above example is a sharp tooth of an Eohippus, which dates to roughly 50 million years ago. Eohippus was a North American equid ungulate, and was much smaller than the horses of today.

mesohippus
Mesohippus tooth, Middle Eocene Epoch. Badlands, South Dakota. Gift of Ellen B. Wells.

Somewhat newer is the tooth from the Middle Eocene (30-40 million years ago) Mesohippus. Our tooth was discovered in South Dakota, and is one of the low crowned teeth distinctive of the genus. The Mesohippus had these grinding teeth behind the front teeth, where the bit fits in the mouth of today’s horse.

Picture of a reconstructed fossil of Mesohippus barbouri at the Harvard Museum of Natural History. Photo frpm Wikimedia Commins, by David Starner, 2010.
Picture of a reconstructed fossil of Mesohippus barbouri at the Harvard Museum of Natural History.
Photo from Wikimedia Commons, by David Starner, 2010.

Also included are two far more recent teeth. One is from Nannippus, an extinct North American horse of the Pliocene Epoch (about 3 to 4 million years ago). The other is from Hipparion, which may have lived as recently as 700,000 years ago in the Pleistocene Epoch.

Nannippus tooth, Pliocene Epoch. Polk Co., Florida. Gift of Ellen B. Wells.
Nannippus tooth, Pliocene Epoch. Polk Co., Florida. Gift of Ellen B. Wells.

These teeth are much larger and recognizable as horse teeth. Hipparion much more closely resembled modern horses, though specimens found have been about the size of small ponies.

Hipparion tooth, Pleistocene Epoch. Polk Co., Florida. Gift of Ellen B. Wells.
Hipparion tooth, Pleistocene Epoch. Polk Co., Florida. Gift of Ellen B. Wells.

We were fascinated to learn a little bit about the evolution of horses by opening that box. We’re currently storing the teeth, and look forward to learning more about these early equine species! Do you know more about prehistoric horses? And what’s the strangest thing you’ve ever found in a library? Get in touch to share with us!

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