That would be in keeping with how vexing bryozoans are to biologists in general. They seem to defy classification. In phylogeny, you can usually categorize an organism by its anatomy or its embryonic development. Most animals form their gastrointestinal tract from the endoderm, which is the innermost layer of an embryo. But adult ectoprocts form their guts and all other internal organs from the epidermis and the mesoderm. And that's only after they go through a larval stage where they destroy all of their internal tissues and create new organs. Most early embryos form a dent in the ball of cells that will become either the anus or the mouth, and are called deuterostomes or protostomes accordingly. Human are, incidentally, deuterostomes, which means we all begins as buttholes. Moss animals also develop a dent, but it then disappears, and a different pore becomes the gut.