Illustration of Ophthalmosaurus marine reptiles swimming, British marine reptiles from the late Jurassic period (165 to 150 million years ago). Ophthalmosaurus belonged to the ichthyosaur group, which were similar to dolphins with long streamlined bodies, long snouts and powerful tails. They also had massive eyes (the name ophthalmosaurus means 'eye reptile') allowing them to hunt squid and fish at great depths. Ichthyosaurs were viviparous (gave birth to live young).