Hunters of Jurassic Seas

Allothrissops mesogaster

Allothrissops was about 60 centimetres long, fast, and ate other fish. It had a streamlined body with a deeply forked tail and very small pelvic fins.

The red label marked ”Orig.” denotes this fossil as a type specimen — the specimen upon which the scientific description of the genus Allothrissops is based. It was described by Orvar Nybelin in 1964.

Stenopterygius

The legs of ichthyosaurs looked like paddles, an adaptation to a life in water. The larger ”paddle” seen here is the left front leg, and the smaller is the left rear leg.

Ichthyosaurs often had only three or four toes, but there were many small bones in each, up to 24 per toe.

Stenopterygius

These skulls of Stenopterygius are typical of ichthyosaurs, with their elongated snouts, large eye sockets, and nose openings directly in front of the eyes. The pointy snouts with many small, narrow teeth indicate that they ate fish.

The smaller skull is from a young animal with a typical ”baby face”; its eyes are very large in relation to the skull.

Stenopterygius

The legs of ichthyosaurs looked like paddles, an adaptation to a life in water. The larger ”paddle” seen here is the left front leg, and the smaller is the left rear leg.

Ichthyosaurs often had only three or four toes, but there were many small bones in each, up to 24 per toe.

Temnodontosaurus

This fossil shows the upper and lower jaws from the front section of a giant ichthyosaur’s snout. Temnodontosaurus specialized in eating giant squids, large fish and other marine reptiles. That can be seen from the large, sturdy and pointed teeth.

Temnodontosaurus had the largest eyes of any vertebrate ever, and it could probably see at depths of up to 1600 metres. 

Liopleurodon ferox

The teeth of the meat-eating pliosaur Liopleurodon ferox were firmly set in its jaws with long roots. The teeth were as large as those of mosasaurs of the Cretaceous Period.

Liopleurodon had a short neck and a large head with terrifying teeth that could tear apart the flesh of dead animals floating in the sea. They also ate very large ammonites and fish, but preferred ichthyosaurs and other plesiosaurs.  

Machimosaurus

This blunt conical tooth with lines along the sides is typical of the extinct crocodile Machimosaurus, which means ”attacking lizard”. Its teeth were specialized for crushing the shells of turtles. Machimosaurus, which could be over nine metres long, was the biggest crocodile of the Jurassic Period and the only marine crocodilethat did not eat fish.

Stenopterygius

This fossil shows the sclerotic ring — the bony ridge encircling the eye. Sclerotic rings are found today in many reptiles and in all birds. They helped the eyes to withstand changes in water pressure when the ichthyosaur dived for its food.

Ichthyosaurs had the largest eyes among vertebrates of all time. With their excellent vision, they could dive to depths over 1000 metres to hunt their prey, without the sort of echolocation system that modern toothed whales have.   

Stenopterygius

These skulls of Stenopterygius are typical of ichthyosaurs, with their elongated snouts, large eye sockets, and nose openings directly in front of the eyes. The pointy snouts with many small, narrow teeth indicate that they ate fish.

The smaller skull is from a young animal with a typical ”baby face”; its eyes are very large in relation to the skull.

Passaloteuthis

In the rear part of this squid-like mollusc’s body was a shell with internal chambers. Behind it was a bullet-shaped structure, the rostrum, which acted as a counterweight that helped the animal to steer straight when swimming.

Passaloteuthis was a predator that fed on ammonites and small fish, and was itself eaten by ichthyosaurs. Passaloteuthis was closely related to modern 10-armed cephalopods such as squids and cuttlefish.

Ptycholepis bollensis

Ptycholepis was an armoured fish. The plates on the skull and the thick scales are covered with hard, shiny enamel-like tissue which forms a characteristic pattern. Ptycholepis had small teeth and ate small fish like Leptolepides which you can see in the display case by the wall.

See also Hyllingea, found in what is now southern Sweden — another fish with ornamented scales.