Figure 5 in Ontogeny and evolutionary significance of a new acrotretide brachiopod genus from Cambrian Series 2 of South China

Figure 5. Internal morphology and ultrastructure of Palaeotreta shannanensis gen. et sp. nov. from the Shuijingtuo Formation of southern Shaanxi. A, enlarged ventral posterior end, showing cardinal muscle scars (arrows) and paired vascula lateralia (tailed arrows), ELI-XYB S4- 3 AU-07; B, oblique lateral view of A; C, enlarged ventral posterior end, ELI-XYB S4-3 AV-07; D, lateral view of dorsal posterior end, noting cardinal muscle scars by arrows, XYB S4-3 AV-18; E, enlarged dorsal pseudointerarea and median buttress, ELI-XYB S4-3 AU-12; F, enlargement of the terminal of median buttress of E, note weakly developed median septum; G, fine pores on the exterior of columnar lamella by exfoliation of the primary layer, ELI-XYB S4-3 AU-09; H, I, one layer of the secondary columnar structures on valve margin, ELI-XYB S4-3 AV-09, XYB S4-3 AU-07; J, K, remaining base of columns after exfoliation of the covering lamella of H; L, one lamella of very short secondary columns, ELI-XYB S4-3 AU-08; M, re-crystallization of the columns, note hollow in the centre, ELI-XYB S4-3 AV-13.