The critter of the 17th of April

In a break from trilobites found in Britain, I think it makes sense to present the organism which is currently my profile picture.

This is Microdictyon, an armoured worm from the early Cambrian. It is often classed as a lobopod, though this phylum is not well defined. It is well known from fossils of its sclerites, with some soft-bodied fossils found in China. It has ten pairs of sclerites on its side, matching its pairs of tentacles, and the anterior and posterior are featureless (this image makes the sclerites look like eyes). There are 11 species of Microdictyon, one of which is amusingly called M. anus. 

I am becoming quite fascinated by early metazoan evolution, right up to the Cambrian explosion. Microdictyon  is one of the small shelly fossils of the post-Tommotian Maotianshan shales.