The Spanish ribbed newt has a pretty bizarre defense mechanism - when attacked, it secretes poison and pushes out its ribs until they pierce its skin, creating a row of sharp bones that act like barbs:

The newt has to force its bones through its skin every time it is attacked, say scientists, who have described the form and function of the barbs in detail. [...]

When the newt becomes agitated or perceives a threat, it swings its ribs forward, increasing their angle to the spine by up to 50 degrees.

As it does this, the newt keeps the rest of its body ...

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