These fossil sea urchins are also called sand dollars. It is a group of sea urchins that live at the bottom of the sea once adults. They can only swim freely as larvae, as soon as the round skeleton is formed, the sea urchin remains on the bottom.
Over 150 million years old
These fossil specimens come from the Jurassic period and are between 150 and 200 million years old. The sea urchins are found in Madagascar. Characteristic of this species is the five-fingered petal. These are actually pores with which the animal can move.
It is remarkable that the animals are not yet extinct. After hundreds of millions of years, they still exist in our seas in an almost unchanged form.