Last time we talked about Vertebrates of which have only two body plans and one common ancestor. Here we're going to talk about Arthropod Body plans. The definition of an Arthropod is of being an invertebrate animal and having an Exoskeleton and jointed appendages. This gives six separate subphylum based on six completely different Body Plans which includes two extinct subphylum as well. The living ones are (in order on the picture) Crustaceans (Crabs, Lobsters etc.), Myriapods (Millipedes etc.), Hexapods (Insects, Wingless Insects etc.), Chelicerata (Arachnids etc.). The extinct are Marrellomorphs and Trilobites. The body design in these cases is more widely varied than any other species or genara on the entire planet. Even the extinct groups have proved to be far more diverse than we could have ever imagined, and just like Vertebrates they all have a single common ancestor, although the arthropod ancestor is much older going as far back as roughly 300 MA (million years)!