Arizona, known for its deserts, might seem an unlikely place for sharks. This arid landscape, far from any ocean, typically evokes images of canyons and heat, not marine life. Yet, the question of whether sharks once existed in Arizona invites an exploration into the state’s natural history.
Arizona’s Present-Day Waters
Today, Arizona’s aquatic environments are primarily freshwater systems, including rivers like the Colorado River and man-made lakes such as Lake Mead and Lake Havasu. These bodies of water are entirely landlocked, lacking any direct connection to oceans. The water in these lakes and rivers is fresh or slightly saline, unsuitable for marine sharks, which require high salinity.
Most of Arizona’s streams are intermittent or ephemeral, flowing only seasonally or after rainfall. While some large reservoirs support diverse fish populations, these are predominantly freshwater species adapted to inland conditions. There are no known naturally thriving populations of marine or large freshwater sharks in Arizona’s contemporary waters.
A Journey Through Ancient Seas
Millions of years ago, the landscape that would become Arizona looked very different. During the Paleozoic Era (541 to 252 million years ago), much of the region was submerged under shallow, warm seas. These ancient marine environments were home to life, including corals, crinoids, brachiopods, and various types of fish.
The Mesozoic Era (252 to 66 million years ago) also saw parts of Arizona covered by water. During the Cretaceous period, around 100 million years ago, the Western Interior Seaway extended into eastern Arizona. This seaway was home to marine reptiles and other ancient aquatic organisms.
Discovering Prehistoric Shark Remains
Tangible evidence of ancient sharks in Arizona exists as fossilized remains, primarily teeth and occasionally fin spines. These fossils are found in geological formations that were once part of those ancient seas, particularly within the Kaibab Formation in northern Arizona, including the Grand Canyon rim. This formation, dating back 260 million years to the Middle Permian period, has yielded a diverse array of shark species.
Researchers have identified several ancient sharks from these Arizona deposits. Examples include Kaibabvenator swiftae, a large predator estimated to be up to 20 feet long with serrated teeth, and Diablodontus michaeledmundi, also known as the “Devil Tooth” shark, a smaller bottom-feeder with distinctive horn-like structures on its head. The discovery of these fossils provides a window into a time when sharks were marine predators in what is now the Arizona desert.