Early arthropod had a fancy brain <———click to link to article on Science News website.
I would use this current science discovery during a unit on speciation and/or genetics. I would love to hear students’ ideas as to what factors they think caused or resulted in the Cambrian Explosion. To my knowledge, much of the explanation for the appearance of so many new body forms in such a small period of time is not yet understood. Thus, students could apply their new knowledge of speciation and/or genetics to “unknown” areas of science in the search of greater understanding.
Angela's Science Blog 
Angie,
I like your idea of assessing what students already know by discussing such an interesting period of time in history. I have noticed that many students talk about people or animals just adapting (almost at the drop of a hat) and evolving into something new, so it would be fun to see what they say in terms of such a large emergence of new body forms.