Figure 5 in Phylogeny of the deep-sea cirripede family Scalpellidae (Crustacea, Thoracica) based on shell capitular plate morphology

Figure 5. Scalpellidae to show polymetric development of valves. A–G, ontogenetic sequence of Scalpellum stearnsi Pilsbry, 1890, with progressive development of polymetric outgrowths on the carina (ip, intraparietes), upper latus, inframedian latus, and finally the scutum (G), shown in green. This growth pattern has the effect of moving the umbones to a subapical position (e.g. su, scutal umbo; cu, carinal umbo in G). A–F are modified after Withers (1953: figs 13–19). B, Arcoscalpellum quadratum (Dixon, 1850), inframedian latus, Eocene, Ypresian, London Clay, Sheppey, Kent, UK, showing subepidermal polymetric outgrowth, forming a contact with the scutum and upper latus (NHMUK In. 3440). Note the difference in surface sculpture between the external surface and the outgrowth. C, inframedian latus, Weltnerium nymphocola (Hoek, 1883), in which the polymetric portion of the plate (green) is flush with the rest of the plate, and has an identical sculpture. D, E, carina of Virgiscalpellum sp. nov., upper Campanian, Keswick Pit, Norwich, Norfolk, UK (Wood, 1988), to show polymetric intraparietes (green), which differs in sculpture from the parietal and tectal surface. F, G, carina of Virgiscalpellum beisseli (Bosquet and Müller, in Bosquet, 1857), in which the tectum, parietes, and intraparietes all have an identical sculpture of coarse radial ribs. Same locality. Scale bars: A, 5 mm; B–G, 1 mm.