These are drag-net "fish." The tails and brains of these animals are kept separate from their gills and digestive system. They each have a filter-net that they drag through the water by swimming, catching plankton. Others push the net, "dragging" it ahead of them. Some swim with the tail on bottom and the mouth(s) on top, as in figure one. Others swim with the tail on top and the mouth on bottom, as in figure two. These animals are probably chordates, but probably not vertebrates. The notochord may cross the bridge between the two parts of the animal and run down both. Depending on the location of the attachment point, the notochord may run in either direction in the "net" part, or even run one way and wrap around before running the other. Then again, they may be aliens with radically different cellular chemistry and structure and thus not even members of Kingdom Animalia at all. Their sensory structures could be found on either part, and divided differently in different species. Any other ideas?
Hello, my name is Dan. I am an author, artist, explorer, and contemplator of subjects large and small. I like bacon. I like pizza. I like bacon pizza. I enjoy long walks on the beach, but prefer the mountains. I am a huge fan of Jesus. When I grow up, I want to be just like him and create my own universes.