Sea Monsters: Prehistoric Ocean Predators

1. Marine reptiles originally evolved on land and then went back to the sea.
2. The biggest marine reptile was the 24-metre Shonisaurus, a type of ichthyosaur.
3. Australia’s top plesiosaur predator, the Kronosaurus, had a bite force of 3 tonnes – more than a saltwater crocodile.
4. The mosasaur Prognathodon’s head was so heavy; if it had lived on land, it couldn’t have lifted it.
5. The first sea monster fossils were discovered about 50 years before we found any dinosaurs – we’ve known about them for around 250 years.
6. Sea monsters ruled the oceans for over 180 million years (modern humans have only been around for about 300,000 years).
7. Some ichthyosaurs could swim at speeds of 40 kilometres per hour.
8. Some Australian sea monster fossils have become stunning and valuable opals.
9. We can learn about what sea monsters ate by looking at their fossilised poo, called coprolites.
10. The plesiosaur Albertonectes had 72 neck bones – more than any other animal. We have only seven.

Dolichorhynchops

• Lived 80-90 million years ago 
• Name means “long snout” 
• Approximately the size of a dolphin 
• Fast swimmer that fed on fish and squid 
• Had no external ears, making it possibly deaf to airborne sounds 

Tylosaurus 

• Lived 73-80 million years ago 
• One of the largest mosasaurs 
• Among the largest and most ferocious predators of any era 
• Grew to between 35 and 45 feet long 
• Eyes were as big as grapefruit 
• Had four rows of sharp, cone-shaped teeth to seize and crush prey, and could swallow prey whole 

Styxosaurus

• Lived 80-85 million years ago 
• A member of the plesiosaurs 
• Its neck was 20 feet long — up to half its body length 
• Each of its flippers was the size of an adult human 
• Swallowed hundreds of small rocks to help grind up meals 

Xiphactinus 

• Lived 70-95 million years ago 
• Largest bony fish of Late Cretaceous, reaching 20 feet long 
• Nicknamed the “bulldog” fish because of upwards thrust of jaw 
• Able to swallow prey up to half its length 
• Often fed on a 6-foot fish called a Gillicus

Cretoxyrhina 

• Lived 82-95 million years ago 
• Largest of the Late Cretaceous sharks, reaching 22-24 feet long 
• Cretoxyrhinateeth have been found in Tylosaurusremains, clues that these two predators may have encountered each other 
• Sharks outlasted extinction of all marine reptiles, except sea turtles 
• Was similar in size and role to the modern great white shark

Hesperonis 

• Lived 65-89 million years ago 
• Large flightless bird that swam in the ocean 
• Swam and fed much like modern penguins 
• Grew as big as 5-6 feet long from beak to foot 
• Had teeth in its beak to help with holding prey

This event is wheelchair accessible.

50% visual content rating – Sea Monsters: Prehistoric Ocean Predators has both sound and visual components.

50% aural content rating – Sea Monsters: Prehistoric Ocean Predators has sound components.

If you have any questions about access, please get in touch with us via reception@museum.wa.gov.au or on 1300 134 081.