Illaenus crassicauda

Illaenus crassicauda is a species of trilobites belonging to the family Illaenidae. These trilobites lived in the middle Ordovician and in the Silurian age (443 - 418 million years ago). Fossils of this species have been found in the sediments of Sweden and Russia.

Etymology
The Latin species name crassicauda means "fat-tailed", with reference to the shape of the pygidium.

Description
Illaenus crassicauda can reach a length of about 14 cm. These trilobites are without glabella and without articulation of the tail. The cephalon has a high profile. The large bulbous head are distant from the axis of the head, close to the margin.