FIGURE 3. Tennysonia stellata Busk, 1867, scanning electron micrographs showing skeletal morphology. A–C, SAM A28766 in Phylogenetic position and systematics of the bryozoan Tennysonia: further evidence for convergence and plasticity in skeletal morphology among cyclostome bryozoans

FIGURE 3. Tennysonia stellata Busk, 1867, scanning electron micrographs showing skeletal morphology. A–C, SAM A28766, RIY Bank, Port Elizabeth. A, transverse series of autozooidal apertures separated by smaller kenozooidal apertures on left frontolateral branch surface with exterior wall of branch dorsal surface visible in lower left; B, detail of apertures showing spines; C, spine developed at triple junction between three interzooidal walls which have an ultrastructural fabric of transverse fibres (right). D, E, SAM A28765, RIY Bank, Port Elizabeth. D, transition from free-walled (left) to fixed-walled organization (right); E, enlargement showing sheet-like exterior wall (arrowed) covering kenozooidal apertures. F, NHMUK 2003.10.27.7, Groot Bank, Plettenberg Bay, rows of autozooidal apertures separated by exterior wall calcification in fixed-walled branch. G, H, NHMUK 2003.10.27.13, Groot Bank, Plettenberg Bay. G, development of exterior wall calcification, at varying levels relative to vertical interzooidal walls, over kenozooids and most of the autozooids (apart from 5 apertures which remain open); H, lobes of exterior wall calcification extending between autozooidal series. I–L. NHMUK 34.10.20.4, Port Elizabeth. I, apertures closed by exterior wall calcification, one occluded autozooid having a small central dimple; note apertural spines standing up above level of exterior walls (top right); J, gonozooid with broken brood chamber roof; K, lobate brood chamber roof (left) with denser pseudopores than exterior walls covering kenozooids (lower right); L, detail of pseudopores from brood chamber roof, some partly closed by spines. Scale bars: A, D, G, H: 500 µm; B, E: 100 µm; C, L: 20 µm; F, I, K: 200 µm; J: 1 mm.