Elasmosauridae

Elasmosauridae is a family of marine reptiles within the plesiosaurs, a subgroup of the larger Sauropterygia. Members are distinguished by extremely elongated necks that often account for much of their total length, relatively small heads, and paddle-like limbs adapted for life in the ocean. The family includes numerous genera, with Elasmosaurus as the type genus; other well-known members include Styxosaurus and Albertonectes.

Morphology and adaptations: Elasmosaurids typically possess long, flexible necks with many cervical vertebrae, sometimes more than 70 in a single species. They have broad, flattened bodies and four strong paddles for propulsion. The skull is comparatively small and teeth are generally sharp, suited to catching fish and small invertebrates. The neck’s mobility allowed precise sweeping motions while maintaining a streamlined body for efficient swimming.

Temporal range and distribution: Elasmosaurids flourished during much of the Cretaceous period, roughly from the Early to Late Cretaceous (about 100–66 million years ago). Fossils have been found in various regions, with notable records from North America (including the Western Interior Seaway) and Europe, and in other areas where Cretaceous seas were present.

Ecology and behavior: They were marine carnivores whose long necks may have enabled them to approach prey with minimal water disturbance. Their feeding likely involved small fish and invertebrates, hunted in mid-water or near the sea floor depending on the species and environment. While specifics of hunting strategy vary among genera, the body plan suggests a combination of stealthy predation and open-water foraging.

Notable genera include Elasmosaurus, Albertonectes, and Styxosaurus, among others, illustrating the diversity of this long-necked lineage.