Tylosaurus was an enormous marine reptile that dominated the oceans during the Late Cretaceous period, roughly 90 to 66 million years ago. As a member of the Mosasauridae family, it was a fearsome predator that grew up to 15 meters (50 feet), making it one of the largest marine carnivores of its time. This colossal size raises the question of what such a massive animal consumed to sustain itself in the ancient seas. The answer is found not just in its imposing anatomy, but in the remarkably preserved remains of its final meals.
Evidence of Diet: Preserved Stomach Contents
The most direct and compelling evidence for the diet of Tylosaurus comes from the rare discovery of fossilized gut contents. These findings, which include partially digested bones and teeth preserved within the abdominal cavity of the mosasaur’s skeleton, offer a direct window into its predatory habits. Since acidic digestive processes and decomposition usually destroy soft tissues, the preservation of these contents is highly significant.
One of the most remarkable specimens, a Tylosaurus proriger found in 1918, contained the remains of a plesiosaur, providing concrete proof of its ability to tackle other large marine reptiles. Another specimen from the Pierre Shale in South Dakota, found to contain a mix of different prey, demonstrates the opportunistic nature of its feeding. Paleontologists meticulously identify these remains, which are often heavily fragmented, to reconstruct the predator’s diverse menu. The bones are typically found near the ribcage area, confirming they were inside the digestive tract when the animal died.
The Tylosaurus Menu: Prey Identification
Analysis of these direct fossil findings, combined with indirect evidence from its specialized anatomy, paints a picture of Tylosaurus as a generalist hunter capable of subduing a wide variety of prey. Its powerful jaws were lined with two rows of slightly backward-curved, conical teeth, which were perfectly suited for seizing and gripping slippery or struggling victims. The mosasaur also possessed a double-hinged jaw and a flexible skull, similar to modern snakes, allowing it to swallow large prey items whole or in massive chunks.
The Tylosaurus diet was highly varied, including large bony fish such as Bananogmius and the massive, swordfish-like Xiphactinus. Remains of sharks, including the teeth of smaller species like Cretalamna, confirm that even other formidable marine predators were not safe. Evidence also points to cannibalism or predation on other mosasaurs, as remains of the smaller Clidastes have been identified in the stomach contents of a larger Tylosaurus.
Beyond marine life, this predator also targeted creatures from the surface, including flightless diving seabirds like Hesperornis. The presence of plesiosaur bones in its gut confirms it engaged in macropredation, preying on other large marine reptiles. Furthermore, puncture marks matching Tylosaurus teeth have been found on the bones of a hadrosaur, suggesting it may have scavenged or actively hunted dinosaurs that strayed into the water.
Apex Predator of the Western Interior Seaway
The sheer size and the comprehensive nature of its diet established Tylosaurus at the very top of the food web in its primary habitat, the Western Interior Seaway. This inland sea bisected North America during the Cretaceous period, creating a vast, productive marine ecosystem where Tylosaurus was the undisputed apex predator. Its ability to consume virtually anything it encountered, from small fish to other large marine reptiles, solidified its dominant ecological role.
This position as the ultimate oceanic hunter meant that few creatures could challenge a fully grown Tylosaurus. Its massive body, which could reach up to 15 meters in length, was propelled by a long, muscular tail, enabling rapid bursts of speed for ambush hunting. The ecological function of Tylosaurus is often compared to modern-day apex predators like the Orca or Great White Shark, as it exerted top-down control over the population dynamics of the entire marine environment.