Deep sea discoveries

It’s hard to comprehend just how big marine reptiles were before we humans arrived. In the latest Maritime Museum exhibition, you’ll gain a great size perspective – and learn about what used to live in our waters.

By Ara Jansen


If you had gone for an ocean swim off our coast some 70 million years ago, you wouldn’t be worried about a crocodile or a shark, because you’d more likely be gobbled up by an even larger marine reptile called a mosasaur.

Welcome to Sea Monsters: Prehistoric Ocean Predators, an exhibition at the WA Maritime Museum in Fremantle that explores how three groups of giant marine animals – ichthyosaurs, plesiosaurs and mosasaurs – ruled the sea when dinosaurs ruled the land. Sea Monsters explores how these three groups, originally terrestrial animals, evolved and adapted to the marine environment. 

Developed by the Australian National Maritime Museum in partnership with Queensland Museum, Sea Monsters is the first exhibition of its kind in Australia. 

This family-friendly and interactive exhibition combines real fossils, gigantic replicas, immersive multimedia and hands-on interactives to reveal ancient monsters of the deep. There are gigantic life-sized casts from actual specimens, including a 13-metre long Elasmosaurus which has an extremely long neck and nine-metre marine lizard called a Prognathodon.

“Ichthyosaurs (dating 251 million to 65.5 million years ago) are the most common type of marine reptile in WA that we have found,” says palaeontologist Dr Mikael Siversson, Head of Earth & Planetary Sciences at the Western Australian Museum. “Last year we found skeletons of three of them. They look like a cross between a dolphin and a shark. They’ve been found around areas like Kalbarri and Dandaragan.”

Cast of ‘fish in a fish’ Xiphactinus fossil. Banner image: Close up view of the cast of a 9 metre long Prognathodon mosasaur. Images © Australian National Maritime Museum

In the exhibition, there’s a huge 1.4 metre Kronosaurus jaw, incredible specimens such as an ichthyosaur giving birth and a five-metre-long fish that died after swallowing another fish whole.

These marine animals were bigger than the largest dinosaurs and developed into awesome apex marine predators. The biggest one was the 24-metre Shonisaurus and some could swim up to 40kms an hour. 

The exhibition details the fascinating story of these long-gone sea monsters through the latest science and amazing fossils from Australia and around the world.

The life-size models were made using original specimens and advanced photogrammetry technology, which uses many photographs of an object taken from different angles to create a 3D version.

Dr Siversson says while those large marine animals no longer exist in our oceans, we live in unique times as there has never been one bigger than the endangered blue whale, which can grow to almost 30 metres, about three school buses long.

“Mosasaurs (which were up to 17 metres long) have been featured in the Jurassic World movies and were pretty vicious and very dangerous. They had extra teeth which made it very difficult to escape. Keep an eye out for those teeth in the exhibition!” 

Sea Monsters runs to July 16. For more details and tickets: https://visit.museum.wa.gov.au/maritime/sea-monsters-prehistoric-ocean-predators