Ophthalmosaurus
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| Ophthalmosaurus discus Seeley, 1874 |
Ophthalmosaurus (meaning “eye lizard” in Greek) was an ichthyosaur of the Late Jurassic period (165 to 150 million years ago), named for its extremely large eyes. It had a graceful 6 meter long dolphin-shaped body, and its almost toothless jaw was apparently adapted for catching squid and fish. Major fossil finds of this species have been recorded in Europe and Argentina.
Like other ichthyosaurs, Ophthalmosaurus gave birth to its pups tail-first to avoid drowning them. Skeletons of unhatched young have been found in over fifty females on fossil finds, and litter sizes ranged from two to eleven pups.
Ophthalmosaurus had a body shaped like a tear-drop and a caudal fin like a half-moon. Its front limbs were more developed than the back ones, which suggested that the front fins did the steering while the tail did the propelling. However, Ophthalmosaurus' chief claim to fame is its eyes which were extremely large in proportion to the 6 meter body, at 4 inches in diameter, and suggest that it was probably a nocturnal hunter. The eyes occupied almost all of the space in the skull and were protected by bony plates (sclerotic rings), which most likely served to maintain the shape of the eyeballs[1] against water pressure at depth.
Calculations suggest that a typical Ophthalmosaurus could stay submerged for approximately 20 minutes or even more[2]. The swimming speed of Ophthalmosaurus has been estimated at 2.5 m/s or greater, but even assuming a conservative speed of 1 m/s, an Ophthalmosaurus would be able to dive to 600 meters and return to the surface within 20 minutes.
[edit] In popular culture
- Opthalmosaurus was featured in the third episode of the BBC television series Walking With Dinosaurs, with a male pup being one of the main characters.
- An Opthalmosaurus named "Mo" was a featured character in the movie The Land Before Time IX: Journey to Big Water
