I've been reading about the basal taxonomy of animals recently, and it seems as though there is some controversy surrounding the classification of sponges, ctenophores (comb jellies), and all other animals. One proposal has it that sponges form a monophyletic group, sister to all other animals. Another proposal is that sponges are polyphyletic, with the rest of the animals descended from some group of sponges or another. A third proposal is that in fact ctenophores are the sister group to the rest of the animals.
What does the current state of research on this topic look like? What are the arguments for and against each view? Is there a general consensus?
