High Tech CT Scans Reveal Fatal Cretaceous Clash Between Giant Predatory Fish and Marine Reptile in Ancient Alabama

Scientists use CT technology to identify a Xiphactinus tooth embedded in a Polycotylus fossil, proving a fatal clash in ancient Alabama's Cretaceous seas.

By: AXL Media

Published: Mar 14, 2026, 5:56 AM EDT

Source: Information for this report was sourced from University of Tennessee at Knoxville

A Hidden Conflict Unearthed in Museum Archives

The Western Interior Sea of the Cretaceous period was a densely populated marine environment where survival required navigating a gauntlet of massive hunters. Evidence of the intense competition between these predators was recently rediscovered within the collections of Chicago’s Field Museum. While examining fossilized crocodiles, Professor Christopher Brochu identified a bite mark on the neck vertebra of a Polycotylus, a type of short necked plesiosaur. The bone contained a massive tooth fragment that had been buried and fossilized within the skeletal structure for millions of years. This discovery provides rare, direct physical evidence of a violent interaction between distinct lineages of ancient marine giants.

Digital Dissection via Computed Tomography

To identify the mystery attacker without compromising the integrity of the fragile fossil, the research team employed advanced computed tomography (CT) scanning. This technology allowed the scientists to look inside the vertebra and reconstruct the embedded tooth in three dimensions. University of Tennessee undergraduates Miles Mayhall and Emma Stalker performed a virtual dissection of the specimen, creating a high resolution model of the broken tooth. The digital reconstruction revealed the distinct anatomical signatures of Xiphactinus, a predatory bony fish known for its immense size and formidable dentition, rather than a more typical reptilian predator like a mosasaur.

Challenging the Traditional Cretaceous Food Chain

The identification of Xiphactinus as the culprit shifts the current understanding of predator-prey dynamics in the Mooreville Chalk ecosystem. While marine reptiles are often considered the undisputed rulers of the Cretaceous seas, this fossil serves as a reminder that large predatory fish occupied equally dominant roles. Lead author Stephanie Drumheller notes that nature is rarely as hierarchical as simplified food chain models suggest. The presence of a fish tooth in a large marine reptile’s neck indicates that the lines between the "top" predators and those a few rungs down were frequently blurred in the heat of a territorial or predatory conflict.