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She said the rocks were about 140 to 180 million years old and contained ammonites – spiral-shelled molluscs that lived in the oceans while dinosaurs roamed the Earth.

The mollusc was discovered on the 100-year anniversary of it first being identified and named.

"The blobfish had been sitting patiently on the ocean floor, mouth open waiting for the next mollusc to come through to eat," the pair said.

In the oceans, molluscs and crocodilians radiated into diverse new forms.

Academics said the find had challenged the belief that early molluscs, from a group known as Aculifera, were basic and primitive creatures.