For a creature that can disappear in an instant, the great white shark has a fascinating and complex family history. Scientists have long debated which ancient line gave rise to today’s great white, often relying on isolated teeth. Recently, however, researchers made a significant discovery in Peru.
In January 2025, scientists in Lima announced they had found a nearly complete fossil of Cosmopolitodus hastalis, a shark that swam the oceans about 9 million years ago. This fossil came from the Pisco Basin, which is now one of the driest areas in coastal Peru, about 235 kilometers from Lima. Among the findings was a large jaw containing preserved stomach contents—sardine remains.
Complete shark fossils are incredibly rare because sharks’ bodies are made mostly of cartilage. This makes fossils difficult to come by, often leaving researchers with only teeth to analyze. Mario Urbina, one of the paleontologists, remarked, “There are not many complete shark fossils in the world.”
A Unique Shark Species
The Peruvian fossil represents an extinct mackerel shark closely related to today’s great white. It’s estimated that these sharks could grow nearly seven meters long, with teeth measuring up to 8.9 centimeters. Cesar Augusto Chacaltana from Peru’s geological and mining institute, INGEMMET, noted that the fossil showed exceptional preservation, providing valuable insights into this species’ feeding habits. Urbina highlighted that at that time, anchovies hadn’t yet evolved, making sardines a primary food source.
The Pisco Basin, while a desert today, is rich in marine fossils. Other significant findings from the area include fossils of a juvenile crocodile over 10 million years old and a gigantic river dolphin skull from around 16 million years ago.
Previous Discoveries
This recent fossil isn’t the first to shed light on the great white’s origins. In 2009, a fossil from the same region that preserved 222 teeth and 45 vertebrae added crucial understanding to shark evolution. The Florida Museum of Natural History described it as a rare find, allowing researchers to study how the teeth fit within the jaw.
According to lead author Dana Ehret, this specimen was about 20 years old and measured between 17 and 18 feet long—similar in size to modern great whites. The discovery ignited a debate over the great white’s ancestry, posing two main hypotheses. One group argued for a close relationship with the ancient Carcharodon megalodon, while another believed it descended from broad-toothed mako sharks. The evidence leaned towards the latter, suggesting that the great white is more distantly related to megalodon than previously thought.
Evolutionary Insights from Teeth
Teeth are crucial in understanding shark evolution. The Peruvian fossil displayed a mix of serrated edges—typically seen in white sharks—along with characteristics of broad-toothed makos. Ehret explained it as a transitional form, demonstrating the evolution from one type of shark to another.
This latest fossil doesn’t resolve all disputes about shark lineage, but it reinforces the idea that Peru’s fossil treasures offer significant clues in piecing together the great white’s evolution.
The Importance of These Fossils
The shark fossil record is often incomplete, making detailed reconstruction challenging. However, the fossils found in Peru provide a fuller picture than many isolated teeth ever could. They bridge gaps in our understanding, showcasing how sharks evolved over millions of years.
In the world of paleontology, where each fragment serves as a puzzle piece, complete remains like these allow scientists to tell a more robust story of the great white shark’s lineage. As more discoveries emerge, the origins of one of the ocean’s most fascinating predators will become ever clearer.
For further reading, you might explore more about shark evolution via the Florida Museum of Natural History, which offers insights into how these ancient creatures transformed over time.
