During the Jurassic period, the continent called Pangaea (pronounced pan-gee-ahhh!) began to break up and push up islands amid the oceans. This period of time saw many sea reptiles evolve and dinosaurs were not the only creatures to rule our earth. Jurassic became a golden period for the largest sea creatures ever to live.
It was 149,000,000BC in Oxfordshire below the ancient Tethys Ocean that our planet first saw the emergence of various sea reptiles. All reptiles once lived on the land, however, 75 million years ago, we saw some of the reptiles evolve and take to the seas.
Cryptoclidus
One of these huge sea reptiles was the Cryptoclidus (Pronounced: crip-TOE-clide-us), which belonged to a genus of marine reptiles, called plesiosaurs (pronounced plee-zee-oh-SAWRS), from the Middle Jurassic Period of England.
Cryptoclidus weighed around 8 tons and measured 27 feet (8 metres) in length. On land they appeared clumsy and cumbersome, yet once in the water, they became graceful creatures that used all four of their huge flippers to glide through the water. Cryptoclidus used all four flippers to also paddle speedily through the water, hunting for shoals of fish, crustaceans, and squid-like (no shell) cephalpods.
Cryptoclidus had around 100 interlocking long sharp teeth, which are believed to have been used to sift though mud on the floor to find creatures that might be hiding there.
Known fossil evidence for this reptile is relatively poorly preserved, found mostly in England, Northern France, Russia, and South America.
Opthalmosaurus
Another sea reptile was the Opthalmosaurus (Pronounced: of-THALM-oh-SAW-rus). (meaning 'eye lizard' in Greek). This sea reptile was an ichthyosaur (giant marine reptiles that resembled fish and dolphins) 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 its 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.
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's eyes 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.
The females Opthalmosaurus's 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 head first, 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.
Liopleurodon
Liopleurodon (pronounced: LIE-oh-PLOOR-oh-don) meaning (Smooth-sided tooth) was a genus of Pliosaurs, a family of large, carnivorous marine reptiles which lived during the mid to late Jurassic period (160 million to 155 million years ago).
Liopleurodon was a 150 ton, 25 metre long sea reptile. It was the largest, most powerful carnivore ever to exist on the earth. It's immense size suggests that it was over 100 years old. Liopleurodon had a directional sense of smell which came from two chambers in it's nose which were like ears pin-pointing where a smell was coming from. It had the largest jaws ever known on an animal. Liopleurodon had four huge flippers which each measured 3 metres long and powered it effortlessly through the water.
Despite needing to breath air, Liopleurodon spent its entire life at sea and was unable to leave the water. It would surface to take a large gulp of air and then would lay low in wait of prey. Liopleurodon was a master of ambush and a shark-eater among others. They were fiercely territorial and confrontations with trespassers, including other Liopleurodons, always ended in conflict and violence.
Female Liopleurodons gave birth to live young and most possibly would visit shallow waters to breed.
Liopleurodon was an omnivore which means it ate both plants and meat. But it's main food was sea prey in other sea reptiles. It is primarily known as a carnivorous reptile but when food was scarce it would eat sea plants.
Liopleurodon had no known predators, only natural occurrences such as severe tropical storms could beach this huge, powerful creature. Tropical storms were common during the Jurassic period and many sea reptiles would be victims of such storms. Many sea reptiles became disorientated during the storms and would be washed up and stranded on the beach - unable to get back to the sea. The dinosaurs that lived on the land would then see them as a banquet. Even the mighty Liopleurodon could end up this way. It would lay stranded upon the sand, unable to move and be slowly suffocated by it's huge body. It's massive, powerful jaws could still make a meal out of the largest land reptiles, but most dinosaurs could bide their time until the huge king of the seas eventually passed away.
Huge sea reptiles continued to dominate the oceans and it would be another 90 million years before they disappeared along with all of the land dinosaurs when the comet hit earth and wiped out this race of huge creatures.
Special feature 1 Jurassic Seas: December 2006
Special feature 2 - Kings Of The Skies: January 2007
Special feature 3 - Early Mammals: February 2007
