The Cretaceous sea monster that met its end by swallowing a meal too large

Nature · Published 3 October 2026 Swipe more like this →

In short: Imagine a predatory fish the size of a car, patrolling ancient oceans with a bulldog-like grin and razor-sharp fangs. Xiphactinus was a master of the deep, yet its voracious appetite sometimes proved fatal. Discover the fossilized evidence of a predator that literally choked on its own ambition.

Xiphactinus, a name derived from Greek and Latin for sword-ray, was a formidable marine predator that thrived from the late Albian to the late Maastrichtian periods. Reaching lengths of up to 5 to 6 metres, this massive ray-finned fish resembled a gargantuan, fanged version of a modern tarpon. As a member of the Ichthyodectiformes order, it occupied the Western Interior Seaway, an ancient ocean that once covered much of central North America.

The creature's predatory nature is well-documented in the fossil record. At least a dozen specimens of Xiphactinus audax have been discovered with undigested prey still inside their stomachs. The most famous example, unearthed by George F. Sternberg, is a 4.2-metre fossil containing a nearly perfectly preserved 1.9-metre Gillicus arcuatus. Scientists believe the predator died shortly after this final meal, likely because the struggling prey ruptured an internal organ during the swallowing process.

Despite its status as an apex predator, Xiphactinus was not invincible. Evidence suggests that dead or injured individuals were scavenged by sharks like Cretoxyrhina and Squalicorax. One specimen of Cretoxyrhina, collected by Charles H. Sternberg, actually contains the remains of a Xiphactinus within its own fossilized stomach. While Xiphactinus was once considered as a candidate for the Kansas state fossil, that title was ultimately awarded to the mosasaur Tylosaurus.

The legacy of Xiphactinus has occasionally been distorted by fringe claims. In the 1980s, a fossilized neural spine of the fish was misidentified by a museum exhibit as a 'unicorn' horn belonging to a biblical creature. Such interpretations were rejected by both the scientific community and major creationist organizations, leaving the true, remarkable story of this Cretaceous giant to be told through its genuine, albeit occasionally gluttonous, fossilized remains.

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