Gronausaurus

Gronausaurus lived about 139 to 137 million years ago, during the Early Cretaceous period.4

Its fossils were found in a clay pit near the city of Gronau, Germany, in 1910. Workers dug them out with pickaxes and accidentally broke many bones.1

The only known skeleton is missing most of the skull bones, many neck vertebrae, and some limb bones.2

Gronausaurus had special cavities under the bones of its chest and back that helped stabilize its muscles when swimming.2

Many scientists now think Gronausaurus is actually the same species as Brancasaurus, just a fully grown adult.1

It lived in a large freshwater lake that sometimes became salty when the sea flooded in.1