Ophthalmosaurus is an ophthalmosaurid ichthyosaurian reptile from the Late Jurassic of the United Kingdom, France, Greenland, Mexico, and the United States of America. It was named in 1874 by Harry Govier Seeley. It is one of the most studied ichthyosaurs, as well as one of the most common and unique.
Physiology
Ophthalmosaurus was an ichthyosaur with a sleek, streamlined body, 4 flippers, a long tail with a shark-like fin on its end, a large fin on its back, a conical head with large jaws, and large eyes on the sides of its head. Its body would have been covered in scaly skin.
Diet
Ophthalmosaurus was a predator, preying on fish and cephalopods. Its teeth were small yet sharp, and were used to get a hold of slippery prey.
Ecology
One of Ophthalmosaurus' key features was its large eyes; they were large in proportion to its body, and were protected by bony sclerotic rings, which would have maintained the shape of the eyeballs. This would allow Ophthalmosaurus to dive deep into the ocean, and would make it either a bathypelagic or nocturnal ichthyosaur, which would come in handy, since the pliosaurs, giant plesiosaurs with short necks and crocodile-like heads, were apex predators that swam in the epipelagic zone; it is even known that Ophthalmosaurus were subject to bouts of joint pain (caused by decompression sickness) when avoiding the plesiosaurs due to coming up too quickly, similarly to modern whales. Along with this, it cruised through the water at a speed of 5.6 miles per hour, and could stay submerged for 20 minutes; with adaptations like these, we can assume that it could dive a depth of 600 meters and return to the surface within 20 minutes. As an ichthyosaur, Ophthalmosaurus would have given birth to live young; along with this, pups were delivered tail-first in order to prevent any chances of drowning.
In popular culture
Ophthalmosaurus was featured in the 3rd episode of the 1999 documentary Walking with Dinosaurs, where it is shown as moving in large groups during the day and hunting at night; as well as this, it is breeding season for the ichthyosaurs, so they start to reproduce. Baby Ophthalmosaurus have to hide in reefs in order to obscure themselves from the Hybodus that prowl the seafloor, while adults have to be wary of the apex predator of the Jurassic oceans, the (egregiously-oversized) Liopleurodon.