Excuse me? I think you are the one to have cut the classes. Cambrian explosian appeared about 570 million years ago. Before that only one celled creatures and algae were around and not for 2.5 billion years. Gee, really?? Hmm, these don't look like "only one celled creatures and/or algae" -- in fact, they look like precambrian trilobite precursors:
![](http://www.paleobase.com/gallery/Metas/Spriggina.jpg)
Care to pull the other leg now?