Metriorhynchus

Metriorhynchus is an extinct genus of marine crocodyliform that lived in the oceans during the Middle to Late Jurassic. Metriorhynchus was named by the German palaeontologist Christian von Meyer in 1830.One strong piece of evidence to suggest that Metriorhynchus spent most of its life in the water‭ ‬is the presence of salt glands.‭ ‬These salt glands are found in many marine animals and work by extracting excess salts from the blood so that they can be excreted externally in a concentrated form.‭ ‬By having an active gland constantly removing salt from the blood,‭ ‬marine creatures,‭ ‬including Metriorhynchus would have been able to drink seawater as well as eat other marine animals that would have had a higher salt content than land animals.

It is not known for certain if Metriorhynchus spent all of its time in the water or if it returned to the land.‭ ‬On land Metriorhynchus would have certainly been more cumbersome,‭ ‬as evidenced by its marine specialisations,‭ ‬but it may have had too for special tasks such as laying eggs,‭ ‬just like turtles have too.‭ ‬While other marine reptiles like icthyosaurs almost certainly gave birth to live young,‭ ‬it needs to be remembered that these evolved from different lines,‭ ‬and that Metriorhynchus had more immediate terrestrial ancestors,‭ ‬meaning that it may not have had enough evolutionary time to develop live birth at sea. No Metriorhynchus eggs or nests have been discovered, so little is known of the reptile's lifecycle, unlike other large marine reptiles of the Mesozoic, such asplesiosaurs or ichthyosaurs which are known to give birth to live young out at sea. Where Metriorhynchus mated, whether on land or at sea, is currently unknown. The name Metriorhynchus means "Moderate snout", and is derived from the Greek Metrio- ("moderate") and -rhynchos ("snout").

Even though Metriorhynchus was an effective predator, it was vulnerable to predation from apex predators such as Liopleurodon which could grow to 7 meters in length. Since Metriorhynchus had lost its osteoderms, "Armour scutes", to become more efficient swimmers it would have had little defense against larger marine predators.

Metriorhynchus was a versatile and opportunistic predator, predated upon both the armoured belemnites, fast moving fish and the giant filter feeding fish Leedsichthys. Occasionally it was also capable of capturing flying animals such as the pterosaurs and scavenging on plesiosaur carcasses on the seafloor.