Bones discovered over 30 years ago in the Waipara River in Canterbury have now been identified as the elasmosaurs - a carnivorous ocean reptile. Likened to the mythical Loch Ness Monster, the elasmosaur is one of many prehistoric giants.
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Here are eight sea monsters that once cruised in the earth's waters.
1. Sarcosuchus imperator - giant crocodile
Also known as the "SuperCroc", this giant crocodile lived around 110 million years ago and was as long as a bus.
Unlike most creatures that stop growing when they have reached adulthood, this massive crocodile kept growing throughout its lifespan and could weigh up to 10 tonnes. It lived in the abundant and lush sub-Saharan Africa and filled up on large prey - including dinosaurs.
2. Liopleurodon - giant reptile
This Jurassic carnivorous creature grew to almost seven metres in length, with its jaws alone estimated to be three metres long. Classified as a pliosaur, they were known as the "King of the Ocean" for their predatory skills. Although slow, they were incredibly agile - slicing through the water flapping its four flipper wings that worked like paddles. It dominated the food chain, consuming other reptiles, fish and squid.
3. Megalodon - giant shark
Forget the great white shark that grows to around six metres in length, some 28 to 1.5 million years ago a far greater shark lurked the oceans. The megalodon was a violent predator with teeth that were almost 20cm long. It was believed to have the most powerful bite of any creature who ever lived. Growing to over 18 metres, the megalodon dined on whales, dolphins, fish and even giant turtles.
Megalodon teeth. Photo / Carol Edwards
4. Archelon ischyros - giant turtle
Living 70 million years ago, this giant turtle could grow to more than four metres long and almost five metres wide. Living in shallow seas known as the Western Interior Seaway, it didn't have a solid shell but a skeleton that was supported by a leathery sheath. This carnivorous creature ate fish and, like the modern turtle, would bury its eggs beneath sand.
5. Jaekelopterus rhenaniae - giant scorpion
Image / Simon Powell
This mammoth scorpion grew to over two metres in length. Its claws were a deadly 45 centimetres in length. Living around 400 million years ago, it was a skilled predator that dwelled in fresh-water rivers and lakes. It would ambush fish, slicing them with its claws. However, it also wasn't averse to eating its own kind.
6. Dunkleosteus - giant fish
Slow but formidable, the force of this fish's bite could match the T-Rex and it was certainly more powerful than any modern-day sharks. Growing to almost 10 metres long, weighing some 4 tonnes, its mouth could open wide and fast, suctioning its prey into its mouth before using its long blades to crush the bones. It would also feast on its own kind sometimes.
7. Livyatan melvillei - giant whale
This killer whale lived around 13 million years ago alongside giant sharks. It grew to 18 metres in length, which is about the same as the modern sperm whale. However, unlike the modern sperm whale, this whale had teeth that could measure 36 centimetres long and was one of the largest predators ever discovered.
8. Mosasaurus - giant lizard
This colossal lizard had a head shaped like a crocodile and a mouth filled with deadly teeth. It lived around 90-65 million years ago and could grow up to 18 metres in length. Classified as a pliosaur, it most resembles a modern-day lizard, albeit significantly larger and more lethal. It ate sharks and other large fish as well as sea birds and turtles.