The previous post described a possible link between sponges and cnidarians that had previously been alluded to in a post on July 18, 2013. In a post before that, I had listed references helpful in understanding the protostome-deuterostome link. But none to date have mentioned the following reference.
Wainright, Patricia O., Gregory Hinkle, Mitchell L. Sogin, and Shawn K. Stickel. 1993. Monophyletic Origins of the Metazoa: An Evolutionary Link with Fungi. Science, 260:340-342.
Their abstract contains the statement that they inferred from their data "that the animals and fungi share a unique evolutionary history and that their last common ancestor was a flagellated protist similar to extant choanoflagellates." I had not annotated their article in my reference list and just this week ran across the issue with it while looking for something else.
All groups of living organisms were undoubtedly very closely related in their early beginnings. But their work was probably part of my subconcious in noting the amoeboflagellates were likely precursors of choanoflagellates and the colonial Proterspongia leading to the sponges.