Britain’s largest ichthyosaur found in the UK’s smallest county.

Ichthyosaurs evolved from a terrestrial ancestor that returned to the sea. They lived exclusively in the water and gave birth to live young.  


The very first ichthyosaur brought to the attention of science was discovered in 1811 and 1812 by Mary and Joseph Anning, in Lyme Regis, Dorset, along the Jurassic Coast.   

Ichthyosaurs are a specialized group of marine reptiles that lived in the water whilst dinosaurs walked on land. They are not swimming dinosaurs.   

More than 100 species of ichthyosaurs have been discovered and they have been unearthed all around the world. Some have even been found with unborn young still inside them. 

Ichthyosaurs this large and this complete are incredibly rare and are normally only found in Germany and North America. Of the few large ichthyosaurs discovered in the UK, generally only partial or fragmentary skeletons have been found, which are mostly displayed behind glass and largely inaccessible to researchers. Historically collected UK specimens also have poorly recorded information, with details of where they were found and their age often completely unknown.   

The size and completeness of the Rutland Sea Dragon will aid in helping to identify other large, but much less complete, ichthyosaurs found in the UK that are already in museums.   
If the identification of the ichthyosaur as Temnodontosaurus trigonodon is correct, this will provide new details on the geographic range of the species.   

Rutland’s bedrock is entirely Jurassic in age and spans the period between about 195 and 160 million years ago, with the oldest rocks in the southwest and the youngest in the west. The ichthyosaur was found in clay-rich rocks dating from approximately 180 million years ago, during the Early Jurassic Period. These are known as the Whitby Mudstone Formation after their best exposure, known as the Type Area, on the Yorkshire coast. Study of the other fossils found with the ichthyosaur such as ammonites, relatives of present-day squid and octopus, will help to date the find more precisely. The high proportion of clay in the Whitby Mudstone Formation makes it relatively impervious to water and this was a key factor in the siting of Rutland Water.