Australian Mesozoic Marine Reptiles

Marine reptiles
"Addyman Plesiosaur"
Cimoliasaurus maccoyi (a small plesiosaur)
"Dave" (a plesiosaur)
Umoonasaurus ("Eric") (a small pliosaur)
"Gingin Mosasaur"
Kronosaurus queenslandicus (a BIG pliosaur)
Leptocleidus clemai (a small pliosaur)
Platypterygius longmani (an ichthyosaur)
Woolungosaurus glendowerensis (a plesiosaur)
Richmond Pliosaur


Australia's inland sea (Early Cretaceous)
Australia consisted largely of isolated land masses surrounding a vast but shallow inland sea for most of the Cretaceous. It is for this reason that dinosaur remains are found only in a few small areas of the continent, and many of these are the remains of animals that washed out to sea after dying to become preserved in marine sediments. Not surprisingly, given that most of the continent was under water at the time, the remains of marine reptiles are more wide spread. They tend to get less attention than the terrestrial (or aerial) creatures of the Mesozoic, even though they came in many interesting, and downright frightening, forms. Ichthyosaurs (meaning "fish reptiles") resembled a cross between a dolphin and a shark. Plesiosaurs and some of the smaller pliosaurs looked something like a cross between a seal and a snake. Some of the mega-pliosaurs, which included the largest and meanest looking carnivores that the world has even known, are thought to have reached the size of some of the largest of modern whales. Mosasaurs were distant relatives of modern monitor lizards (and perhaps snakes) and looked a bit like a giant crocodile.

These marine reptiles were not dinosaurs, and were not as closely related to them as were pterosaurs (flying reptiles), crocodiles or birds. Mosasaurs were related to modern monitor lizards such as the Komodo dragon and the Australian goanna. A relative of the mosasaurs may have also been the ancestor of snakes, losing their paddle-like legs through evolution to make them more streamlined swimmers. Snakes and lizards are only very distantly related to the Archosaurs (dinosaurs, birds, pterosaurs, crocodiles) or the other marine reptiles (plesiosaurs, pliosaurs, ichthyosaurs).

The similarity between these extinct marine reptiles and modern marine animals is no accident. Some shapes are just so well adapted to marine living that they are repeated over and over again by creatures that may not be even closely related, a condition known as covergent evolution. All of these marine reptiles were air breathers that had to return to the surface periodically or else drown, like modern whales and dolphins, and most species seemed to have prefered shallow waters rather than deep ocean.

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