Arcuatoscalpellum, Gale, 2016

Gale, Andrew Scott, 2016, Phylogeny of the deep-sea cirripede family Scalpellidae (Crustacea, Thoracica) based on shell capitular plate morphology, Zoological Journal of the Linnean Society 176 (2), pp. 266-304 : 297

GENUS ARCUATOSCALPELLUM GEN. NOV.

FIGURE 4N–S

Type species

Scalpellum arcuatum Darwin, 1851b . Cretaceous, Albian–Cenomanian, UK.

Diagnosis

Basal scalpellines in which the carinolatus is slightly taller than broad, umbo apical, carinal margin convex, carina with median ridge; upper latus margin gently concave; inframedian latus surface not differentiat- ed; on the interior, the surfaces overlapping the carina and upper latus are similar; external sculpture with strong radial ridges, weak reticulation.

Derivation of name

In eponymous reference to the type species.

Referred species

Scalpellum (Arcoscalpellum) comptum Withers, 1910 and Scalpellum trilineatum Darwin, 1851b . Cretaceous.

Remarks

Material of the type species is illustrated here ( Fig. 4M– S ). Arcuatoscalpellum gen. nov. is the most basal scalpellid known, and ranges from Aptian to latest Maastrichtian in age. It shares many characters with Cretiscalpellum , including the sculpture and simple triangular morphology of the carinolatus.

Figures

Figure 4. Comparative morphology of out-group and basal scalpellid. A, B, Cretiscalpellum aptiensis Withers, 1935, capitulum, in lateral and carinal aspects. Bargate Stone, upper Aptian, Shackleford, Surrey, UK. Holotype, BGS 49533 (original of Withers, 1935, pl. 13, fig. 1). C–L, Cretiscalpellum striatum (Darwin, 1851b): C, carina (NHMUK IC 1191); D, F, rostrum NHMUK IC 1192); E, subcarina (NHMUK IC 1193); G, scutum NHMUK IC 1194); H, tergum (NHMUK IC 1195); I, carinolatus (NHMUK IC 1196); J, subcarinolatus (NHMUK IC 1197); K, inframedian latus (NHMUK IC 1199); L, upper latus (NHMUK IC 1200). Upper Campanian, Upper Chalk, Keswick, Norwich, UK. M–S, Arcuatoscalpellum arcuatum (Darwin, 1851b). M, exterior of rostrolatus (NHMUK IC 1221). N, exterior of scutum (NHMUK IC 12222). O, P, carinolatus (original of Collins, 1974, pl. 11, fig. 10, NHMUK In. 61368). Q, tergum (original of Collins, 1965, pl. 90, fig. 12, NHMUK In. 64259). R, S, carina in carinal and lateral aspect (NHMUK In. 1754). M, N, Upper Albian, Gault Clay. M, cristatum subzone (Bed 8i), Folkestone, Kent. O–Q, orbignyi subzone, Paddlesworth, Kent. R, S, Dunton Green, Kent. Note similarities in sculpture and overall valve morphology; the taxa differ importantly in the presence of a subcarina and subcarinolatus in Cretiscalpellum; these are absent from Arcuatoscalpellum gen. nov. Scale bars: A–B, 10 mm; N, Q, 5 mm; R, S, 2 mm; C, G, H, O, P, 1 mm; D–F, I–M, 0.5 mm.