Elasmosaurus was a marine reptile that lived during the late Cretaceous period, around 80 million years ago. It belonged to a group called plesiosaurs, characterized by their long necks and small heads. Elasmosaurus had a neck that was about 7 meters long, making it one of the longest-necked marine reptiles known. This creature could grow up to 14 meters in length and primarily fed on small fish and other marine animals. Its long neck allowed it to reach prey in the water while its paddle-like limbs helped it navigate through the ocean. Elasmosaurus is often depicted as a gentle giant of the prehistoric seas.