Cymbospondylus was 10 metres (33 ft) long so it is one of the largest ichthyosaurs. Adult Cymbospondylus hunted probably in deep offshore water.
Although Cymbospondylus was very large it was not a threat to other marine reptiles, such as Nothosaurus. The teeth of Cymbospondylus were so small that it was unable to grasp and held large large animals, not to mention to kill them.
Instead Cymbospondylus was adapted for catching and holding on to small and medium-sized fish, belemnites, and cephalopods such as ammonites.