‘Devil Tooth’ one of many sharks to leave mark in Arizona’s past

David Elliott

DiablodontusAn ancient shark with menacing head spikes that survived a mass extinction is the latest fossil find in Arizona’s Kaibab Formation that has drawn the attention of the Discovery Channel as part of Shark Week.

Lead author John-Paul Hodnett, who earned his biology degree from Northern Arizona University, and NAU geology professor David Elliott described the shark in a recent paper. Last year, Elliott wrote about another shark discovery. Below, Elliott offers some additional insight about the research.

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David Elliott

by David Elliott
Geology Professor

About 260 million years ago, during the Permian period, much of Arizona was covered by a warm, relatively shallow sea. Sediments deposited in this sea form what is now the Kaibab Formation, a sequence of yellowish limestone that forms the rim of the Grand Canyon and can be seen exposed on south campus at NAU.

Although the extensive invertebrate fauna from the Kaibab has long been studied, very little work has been done on the vertebrates until recently, when initial collecting by a local hobbyist and NAU graduate, Tom Olson, was expanded by NAU undergraduate JP Hodnett and me.

The work has resulted in a series of papers on the Kaibab sharks, organisms represented mostly by isolated teeth and fin spines. Initial study of the sharks represented in the collections suggests that there may be as many as 40 different taxa represented, making this the most diverse fauna of its age in the world.

At present, nine of these taxa have been described, identifying a range of sharks from the large Kaibabvenator swiftae, which might have been up to 12 feet in length and was probably the top predator in the Kaibab sea, to Diablodontus michaeledmundi, a small, 2- to 3-foot shark similar to modern hound sharks that fed near the bottom on small fish and invertebrates.

This study provides a window into life in the ocean at a time when bony fish were only starting to become important, and sharks were by far the most abundant vertebrate organisms. As this study progresses, it will provide data to help us understand more about the ecology of this ancient sea and document the diversity of vertebrates in the ocean prior to the end-Permian extinction, the most severe in the Earth’s history.