Sheril over at The Intersection seems to be confused about what the coolest invertebrate is. She goes so far as to call out PZ about his hyper-infatuation with Cephalopods. Let’s face it there is no way an echinoderm, especially a holothurian, can come anywhere near the coolness of a Mollusk. There is a reason why we at DSN have a whole category here dedicated to Cephalopods and not one dedicate to our water-vascularized friends. It’s just hard to get excited about a sea cucumber that either feeds on sediment muck or filters muck out of the water column and not much else. Or an organism whose idea of fun is spewing its organs all over you or creating poop trails. Do sea cucumbers do this, or this, or this? I don’t think so. If you need more fodder check out this site and see Vermeij discuss how Mollusks are winning the ocean’s arms race. Mollusks get both larger and smaller than all the Echinoderms and they are more diverse both in terms of number of species and the ecological niches they fill.
If you don’t believe me that Mollusks are cooler than sea cucumbers watch the videos below.