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"Gingin Mosasaur"
Classification Indeterminate

Gingin Mosasaur
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CLASSIFICATIONIndeterminate, Mosasauroidea, Squamata
AGEEarly Cretaceous (Turonian-?Santonian) 91-86 MYA
LOCATIONNear Gingin, Western Australia (Molecap Greensand)
SIZE2.6 metres (8.5 feet) long

Known from only three small bones collected in the Gingin area of Western Australia in 1956, it is thought that this mosasaur was related to Platecarpus from the Early Cretaceous of Kansas in the United States. The material consists of a single ulna and two paddle bones. When compared to Platecarpus, the Australian animal would have been only about 2.6 metres in total length.

The only other evidence for mosasaurs in Australia are three dorsal vertebrae found near Exmouth, also in Western Australia. These date to the Late Maastrichtian at the very end of the Cretaceous Period. The living animal has been estimated at around 6-8 metres (20-25 feet) long, but has not been assigned to any specific mosasaur family. Given the number of mosasaur species known from nearby New Zealand, the lack of Australian fossils may be due to the fact that most of Australia's best marine reptile fossil formations pre-date the evolution of mosasaurs.

Mosasaurs were related to monitor lizards (like the Australian goannas and the Komodo dragon) and were completely adapted to life in the oceans. Their limbs had been modified into paddles and their tails, in most mosasaur species, were flattened like those of an eel. Platecarpus probably did not have tail fins as large as some of the other Mosasaur species, however it did have larger paddles.

One Platecarpus specimen was found with damage to some of the tail bones, which later became infected while the creature was alive. On closer inspection the tipof a shark's tooth was found embedded in one of the tail vertebrae, indicating a shark attack as the likely cause of the damage. With so many large, and presumably fierce, predators roaming the Cretaceous oceans it was inevitable for some of them to fight with others. Some of the large pliosaurs have been found with the remains of plesiosaurs in their abdominal cavity, and it is thought that they even attacked mosasaurs on occasions. Mosasaurs themselves fed on fish and ammonites (large shelled cephalopods a bit like a modern nautilus), and probably anything small enough that moved (remains of sharks, primitive diving birds, and other mosasaurs have been found in fossilized droppings). Platecarpus however seems to have fed on nothing but fish, although fish up to 1.2 metres in length were sometimes consumed.

It is thought that a relative of the mosasaurs, Pachyrachis, gave rise to modern snakes. It seems to have lost its paddle-like limbs in order to become a more streamlined swimmer. The fact that modern snakes and monitor lizards are therefore related (if only distantly) is of no surprise - both are the only modern reptiles to be able to "smell" with a forked tongue, and the Gila monster (a primitive relative of the monitor lizards) is the only venomous lizard known today, a trait shared by some snakes. The highly kinetic skulls of mosasaurs were also similar in design and function to those of modern snakes, with some bones of the skull and jaw being able to move somewhat independantly in order to maneouvre prey further back into their throats.

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