Wiwaxia

Wiwaxia is a very special creature that scientists know little about. It crawled along the ocean floor and is very spiky. It was said to lived during the middle Cambrian Period. Those longer spines project in two rows along the back, and evidently provided some protection from predators. The rest of the upper (dorsal) surface is covered with small, flat, overlapping hard plates, termed sclerites. Each of these little scales was attached with a root-like base and we assume Wiwaxia grew by molting these plates from time to time. Since there are none on the bottom (ventral) surface, the animal partly resembles the slug, a member of the mollusk family. Fossil sizes range from one eighth to two inches.