Elasmosaurus was a genus of long-necked plesiosaur that swam in the oceans of the Late Cretaceous period, approximately 80.5 to 77 million years ago. This massive animal could reach lengths of over 34 feet, featuring four paddle-like limbs for propulsion. Elasmosaurus is famous for its extraordinarily long neck, which measured around 23 feet and contained up to 72 vertebrae. This great size and unusual anatomy suggest a specialized feeding strategy within its habitat, the Western Interior Seaway of North America.
Identifying the Main Food Sources
Evidence from fossil discoveries indicates that Elasmosaurus was a predator focused on relatively small, fast-moving prey that could be swallowed whole. Direct fossil evidence, including preserved stomach contents in related elasmosaurid specimens, confirms a diet consisting primarily of teleost fishes.
The diet also included soft-bodied cephalopods, such as squid and ancient ammonites, confirmed by discoveries of remains like hooklets in the gut regions of plesiosaurs. An elasmosaurid specimen from Kansas, for example, revealed identifiable prey fragments of the small fish Enchodus. This suggests that the animal targeted schooling fish in the pelagic zone, or open water.
The prey items were generally not heavily armored or large, which aligns with the overall feeding mechanisms of the animal. The primary food source appears to have been readily available, mid-trophic level aquatic life. This reliance on smaller prey indicates a seize-and-swallow feeding habit, rather than one involving powerful biting or dismemberment.
Anatomical Adaptations for Feeding
The Elasmosaurus skull was small and triangular relative to its body, but its dentition was highly specialized for catching slippery marine organisms. Its teeth were long, slender, and interlocking, resembling sharp, conical fangs suited for piercing and grasping. This dental structure acted like a fish trap, designed to hold fast to a struggling fish or cephalopod, rather than to cut or crush hard shells or bone.
The jaws were not built for a powerful bite, suggesting the animal was incapable of subduing large or heavily armored prey. The teeth were replaced throughout the animal’s life, ensuring a continuous supply of sharp, functional dentition. This morphology suggests a focus on the quick, efficient capture of small prey items.
The iconic long neck, which was not highly flexible, likely played a specialized role in hunting. The neck’s length may have allowed Elasmosaurus to approach schools of fish stealthily from below or to strike rapidly at prey. By keeping its large body stationary, the reptile could use its head to dart into a school of fish, minimizing the water disturbance that would alert its potential meal.
Understanding the Function of Stomach Stones
Many Elasmosaurus skeletons and those of its relatives are found in association with a collection of smooth, highly polished stones called gastroliths, or stomach stones. These stones were ingested, as they are found in the abdominal cavity, but their function remains a topic of scientific discussion.
One leading hypothesis suggests that the gastroliths acted as ballast, helping to control the animal’s buoyancy and stability in the water column. By adding weight to the lower body, the stones could have aided in maintaining an underwater position or helped the reptile to dive. This mechanism is plausible for a large marine reptile that “flew” underwater using its paddle-like limbs.
A second theory proposes that the stones served as a gastric mill, assisting in the physical breakdown of food. Since Elasmosaurus swallowed its prey whole, the stones could have ground up indigestible parts like fish scales and bones, making digestion easier. The presence of fish remains tightly associated with gastroliths in some specimens lends support to the digestive aid theory as well.