Complex sentence: The phylogenetic position of "Symbion" remains unclear: originally the phyla Ectoprocta and Entoprocta were considered possible relatives of "Symbion", based on structural similarities.
Split into simpler sentences: The phylogenetic position of "Symbion" remains unclear. Originally the phyla Ectoprocta and Entoprocta were considered possible relatives of "Symbion", thanks to structural similarities.