Opthalmosaurus (of-THALM-oh-SAW-rus), (meaning ‘eye lizard’ in Greek). This sea reptile was an Ichthyosaur of the Late Jurassic period, 165 to 150 million years ago, which was named for its extremely large eyes.

It had a graceful 6 metre long dolphin-shaped body, and it’s almost toothless jaw was apparently adapted for catching squid and fish. Opthalmosaurs was one of the oldest marine reptiles and one which was most adaptive to marine life.


Nobu Tamura (http://spinops.blogspot.com), CC BY-SA 3.0, via Wikimedia Commons

How big was Ophthalmosaurus?

Ophthalmosaurus had a body shaped like a teardrop 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, the eyes of Ophthalmosaurus were extremely large in proportion to the 6 metre body, measuring 4 inches in diameter, and suggest that it was probably a night 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. Their eyes were light-sensitive, and they could easily pick out a squid in the darkness.

Ophthalmosaurus could stay submerged under the water for approximately 20 minutes or even more before having to return to the surface for air. Ophthalmosaurus would be able to dive to 600 metres and return to the surface within 20 minutes.


MUSE, CC BY-SA 3.0, via Wikimedia Commons


User:Captmondo, CC BY-SA 3.0, via Wikimedia Commons

Ophthalmosaurus Birth & Babies

Female Opthalmosaurus would gather in their hundreds at the same time each year near shore to give birth to their pups. Each female would give birth to between 2 and 5 pups. The pups were born tail first because if they were born headfirst, they would have drown in the time it took to come out of their mother. Once born, they had but a few seconds to reach the surface of the ocean to take their first breath. Pups would stay together in a creche and swim through coral reefs for safety. They were very vulnerable and in danger from predators such as sharks. Females giving birth would also be in danger from predators.

Sharks had patrolled the oceans long before any sea reptiles and with their acute hearing could hear animals in distress. Therefore, if a female was having problems giving birth, they would most likely become a shark meal.

After giving birth to their pups, the adult Opthalmosaurus would return to the deeper waters of the ocean. The pups would stay near shore until they were older and then join the adults. The same time the following year, hundreds of female Opthalmosauruses would return to the same spot to give birth to the next generation.


Last Updated on 15/07/2022 by