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Object of the Month: Ichthyosaur Fossil

An Ichthyosaur Jaw Fossil  from loans box X1/A

An Ichthyosaur Jaw Fossil from loans box X1/A

December’s Object of the Month is the magnificently preserved fossil of an ichthyosaur jaw complete with an array of sharp teeth. This is a very popular item in our School Loans Collection. The ichthyosaurs were highly successful marine reptiles resembling dolphins. The group first appeared around 230 million years ago during the middle of the Triassic period and reached their ultimate zenith (the greatest number of and degree of biodiversity) during the succeeding Jurassic period (208 million years ago to 144 million years ago.). The word ichthyosaur is derived from the Ancient Greek for ‘Fish Lizard’.

The fossilised teeth of ichthyosaurs tell us a great deal of information about the dietary habits of these fascinating creatures. The tightly packed conical teeth, as can be seen in this fossil, were designed perfectly for catching and slicing into prey. For a long time, the consensus of academic opinion amongst palaeontologists was that ichthyosaurs were dependent upon squid like animals called belemnites and small fish. Nevertheless, the excavation of a near complete fossilised skeleton in Queensland, Australia, over ten years ago, preserves the entire contents of the creature’s stomach at the precise point of death; palaeontologists having identified a number of large, bony fish and hatchling–sized baby turtles.

The discovery made by the palaeontologist Dr Kear of small, U-shaped dental cavities in ichthyosaur jaw bones is a defining characteristic shared by sharks. This indicates that the marine reptiles evolved to kill and tear apart prey through employing the classic shark technique of ‘shake feeding’. These predators were clearly much more deadly than once thought.

Our ichthyosaur teeth and jaw present an illuminating freeze frame of just how effective and efficient a killing machine this creature really was. It is easy to imagine these teeth and jaws in action millions of years ago literally shaking a fish or a turtle to death; tearing its victim apart into finely cut pieces. Therefore, it is no wonder that the ichthyosaurs were an evolutionary success story and were able to thrive in the oceans throughout the Triassic and Jurassic periods.

It is apparent that a major break to the fossil was once repaired using a type of glue resin that can be seen in the image.

Date published: 14 Dec 2016

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