Station: [25] Ichthyosaur

A fish! Or... is it a dinosaur!?

The term "ichthyosaur" translates literally as "fish lizard". Saurians were reptiles and had initially evolved on land. Only later did some species adapt to living in an aquatic habitat. 

A similar process was repeated much later in the Earth's history, when mammals that had evolved on land colonised the oceans as seals, whales and dolphins.

As it happens, the ichthyosaur looks very similar to a dolphin. To move through water and hunt prey species that swim, you need a streamlined anatomy adapted to that habitat. So both mammals and reptiles separately developed similar shapes.

The small ichthyosaur skeleton, most of which has been preserved, is about 180 million years old. By a happy coincidence, it wasn’t flattened by the rock masses lying above it. The reason this fossil was preserved in three-dimensions was because calcium was being deposited in the immediate vicinity of the decaying dinosaur, in part due to bacterial action. As a result, the surrounding mud quickly solidified into a protective carapace. Note the ammonites next to the skeleton. They were the ichthyosaurs’ prey and had sunk to the bottom of the sea.

The many large and small discs at the bottom of the display case are vertebrae from other ichthyosaurs. They lay scattered on the Jurassic seabed and are probably from several individuals. The largest of these vertebrae must have belonged to an enormous ichthyosaur that was roughly between 10 and 15 metres in length – equivalent to between 32 and 48 feet long!

All the finds in this display case come from the Black Jurassic period and were discovered near the town of Altdorf.