Ophthalmosaurus lived during the Early to Middle Jurassic Period from 200-145 million years ago. It was a prey item for many sea monsters, including Hybodus, Metriorhynchus, and even the giant Liopleurodon.
Ophthalmosaurus had a graceful dolphin-shaped body. They measured around 4.5-6 meters long and 1-2 tons in weight, very different from the eel-like shapes of earlier Ichthyosaurs, such as Cymbospondylus, and its almost toothless jaw was well adapted for catching squid; nevertheless it was a speedy pursuit predator.
Ophthalmosaurus was a sea reptile that had stream lined, fish like bodies. These are the oldest of marine reptiles and were perfectly adapted to aquatic life.
Like many fish of the 21st century, Ophthalmosaurus lived in schools of hundreds. Females came from deeper water to give birth. While most sea reptiles returned to the surface and land to lay eggs, Ophthalmosaurus didn't. They instead gave birth to live young. This needs the adults to have them from crawling out of the water and has allowed them to evolve their fish like shapes. A single female had between two and five pups, but because they were air breathers, the young had to be born tail first –– or otherwise, they would have drowned in the time it took them to escape from their mothers. New-born pups only had a few seconds to reach the surface and take their first breath.
From the moment they were born, the little Ophthalmosaurus pups were vulnerable. The Jurassic waters were full of predators and even other adult Opthalmosaurus ate the offspring of others to increase the chance of survival of their own pups. The only real safety was among the crags of coral.
Coral reefs in the Late Jurassic seas were full of baby Opthalmosaurs. Intricate network of caves was their refuge, a safe haven from which they can start to learn about their new world. Unlike adults, the baby Opthalmosaurs had prominent teeth. This allowed them to cope with a variety of tough prey among the coral, but Ammonite shells were too tough for them.
Opthalmosaurus adults were masters of hunting at night. With their enormous light-sensitive eyes, they could pick out squid in the gloom. Their long toothless snouts are streamlined weapons, making it easy for them to snap up fast-moving prey.