The testadon, Armatechinos impenetrabilis, is an armadillo-like erinaceid from the undergrowth of the temperate woodlands of Europe.
The testadon is among the insectivorous undergrowth-dwellers that have kept to their original lifestyle. It is a descendant of the West European hedgehog. The spines of its ancestor have been replaced by a series of hinged, armored plates which can roll up and be drawn together to form into an impregnable, complete sphere when the animal is threatened. When rolled up tightly it is almost impossible to grip or penetrate and even the most determined predator rat finds a meal from this little animal more trouble than it is worth.
The testadon has an overall length of 30 centimeters.
When rolled up the testadon forms a complete sphere.