By Alex Hayers

It may not seem like it now, but back in the Jurassic and early Cretaceous periods, the Jurassic Coast was nothing like it was today. Britain was situated near the equator and high sea levels meant the Jurassic Coast was a large shallow tropical sea.

This is one of many sites worldwide where you can find Mary Anning’s discovery, the ichthyosaur. These carnivorous reptiles were well-adapted for life in the oceans, their large eyes, streamlined bodies, and strong tails allowing them to hunt at great speeds and depths of up to 1.6km beneath the surface.


VOTE NOW for Ichthyosaurs in our Jurassic Coast Big Five competition


All along the Jurassic Coast, and elsewhere in the world, full skeletons can be found of these dolphin-like animals, sometimes with their last meals still preserved within them! Palaeontologists have identified these remains, known as coprolites, to be those of ancient squid, shellfish, fish, ammonites, and sometimes even other ichthyosaurs! It is fascinating to me that we can visually see what something last ate up to 250 million years ago.

Ichtthyosaur fossil Dorset County Musum

Ichthyosaur © Dorset County Museum


Ichthyosaurs are considered to be reptiles, but unlike most modern marine reptiles, they do not lay eggs and they are warm-blooded. Also, like marine mammals, their ancestors first evolved on land before they progressed back into the oceans. They were also air-breathing as they had lungs, not gills, and some palaeontologists therefore believe that they surfaced out of the water like modern day dolphins in an action known as porpoising.

It may sound like I am describing a modern day dolphin, shark, or whale, but actually ichthyosaurs are great examples of convergent evolution, where two completely unrelated organisms adapt similar features as a result of their shared environments. Dolphins and modern marine mammals and ichthyosaurs are separated by over 90 million years of evolution and yet they evolved similar behaviours, morphologies (body shape), and features, even though ichthyosaurs were not mammals.

To visualise that, if you were to take one step for each of the 90 million years, you would have walked around the entire Earth 1347 times! In essence, they are great local evidence for evolution right on our door steps.

Ichthyosaurs have taught us so much about life in ancient oceans such as how and what they ate! They also taught us a lot about evolution as a whole and, despite going extinct, ichthyosaur-like features can still be seen in modern reptiles, fish, and marine mammals today, which just goes to show how successful their adaptations are for life in the oceans. This is why you should vote ichthyosaur!