Figure 2. Some common spine pattern formulae and views of the frontal membrane of ancestralae of Bugula stolonifera. All spine patterns are recorded from the viewpoint of the ancestrula right:left:proximal. (A) Diagram of an ancestrula with the typical 3:3:1 spine pattern cited in the text; (B) 3:3:0 variant spine pattern resulting from a loss of the proximal spine: this spine pattern was the most abundant variant spine pattern accounting for 54% of the variant spine patterns; (C) 3:2:1 variant spine pattern resulting from a loss on the left distal margin; (D) 4:3:1 variant spine pattern resulting from a spine gain on the right distal margin.