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Earth Notes: Arizona’s Ancient Sharks

Shark teeth (Diablodontus michaeledmundi) from the Kaibab formation of Arizona
John-Paul Michael Hodnett
Shark teeth (Diablodontus michaeledmundi) from the Kaibab formation of Arizona

Before it was vast ponderosa pine forest, northern Arizona was covered by a warm, shallow sea. Marine organisms resembling ancient clams, nautiluses, and corals thrived in its waters…and so did several dozen different kinds of sharks.

In fact, the Kaibab formation has the most diverse array of sharks from the Middle Permian era of anyplace in the world.

260 million year-old sediment forms the yellow-gray Kaibab Formation, which stretches across northern Arizona, southern Utah, and southeastern Nevada. The word “Kaibab” is a Southern Paiute word meaning “mountain lying down,” and the layer is composed of limestone, sandstone, and other minerals formed under a shallow inland sea.

It’s in this layer that geologists at Northern Arizona University are making surprising discoveries about ancient marine life. Fossil remains of teeth and fins suggest that around forty different species of shark dwelled within the region.

One of these sharks, known as “Swift’s Kaibab hunter,” was a 20-foot-long apex predator with blade-like, serrated teeth similar to the modern great white shark. Then there’s the “Devil Tooth” shark, named for its unusual pair of horns on top of its head. It was a bottom feeder that grew up to 3 feet long.

At the time, sharks not only were the main vertebrate marine predators; they also filled niches later occupied by bony fish, mammals, whales, and dolphins.

This research offers an intriguing glimpse backward to an era when what’s now Arizona was underwater, some 45 million years before the first dinosaurs appeared.

This Earth Note was written by Danika Thiele and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.

Danika Thiele is a Florida transplant, art enthusiast and environmental science writer. She worked previously as a food security and sanitation volunteer with Peace Corps Nepal. With her background in both agriculture and journalism, Danika combines her curiosity with the natural world to produce stories stemming from nature's peculiarities. You can catch Danika exploring the forest with her adventure partner, Dolly the supermutt.
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