Diotascalpellum, 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 : 297-298

GENUS DIOTASCALPELLUM GEN. NOV.

FIGURES 2A , 6U–Y , 11Q–T , 13K–M , 18A–G

Type species

Scalpellum diota Hoek, 1907 .

Diagnosis

Scalpellines in which there is no specialized contact between the carina and carinolatus, merely a cresentic concavity on the interior of the plate that forms a rim slightly overlapping the upper latus; umbo of carinolatus upright, only slightly incurved, dorsal margin gently convex; inframedian surface of carinolatus well demarcated and slightly inset.

Derivation of name

In eponymous reference to the type species.

Included species

Scalpellum rubrum Hoek, 1883 , Scalpellum indicum Hoek, 1883 , Pollicipes angustatus Geinitz, 1843 , Scalpellum gracile Bosquet, 1854 , and Scalpellum fossula Darwin, 1851 .

Remarks

Cretaceous and extant species of Diotascalpellum gen. nov. have a very similar carinolatus morphology (e.g. Fig. 18A–G). The prevalence and diversity of species of Diotascalpellum in the Cretaceous supports its basal phylogenetic position. The earliest records are from the upper Albian ( D. angustatum ; Withers, 1935).

Figures

Figure 2. A–E, H, Scalpellinae in lateral aspect: A, Diotascalpellum rubrum (Hoek, 1883); B, Regioscalpellum regium (Thomson, 1873); C, Arcoscalpellum michelottianum (Seguenza, 1876); D, Arcoscalpellum sociabile (Annandale, 1905); E, Arcoscalpellum regina (Pilsbry, 1907); F–H, Graviscalpellum pedunculatum (Hoek, 1883); F, ventral (rostral) aspect; G, dorsal (carinal) view; H, lateral view. See Table 1 for details of localities etc. Scale bars: 5 mm.

Figure 6. Evolution of lateral plate morphology, dorsal side: A–E, Amigdoscalpellum truncatum (Hoek, 1883); F–J, Arcoscalpellum sociabile (Annandale, 1905); K–O, Arcoscalpellum michelottianum (Seguenza, 1876); P–T, Regioscalpellum regium (Thomson, 1873); U–Y, Diotascalpellum rubrum (Hoek, 1883). External aspect of carinolatus (A, F, K, P, U); interior of carinolatus (B, G, L, Q, V); external view of inframedian latus (C, H, M, R, W), interior of inframedian latus (D, I, N, S, X); dorsal (carinal) view of capitulum (E, J, O, T, Y). See Table 1 for details of localities. Note the migration of the position of the carinolatus umbo from apical to nearly basal, the progressive incurvature of the umbo, and the development of an upper latus surface. The lower four species are assigned to the Scalpellinae, the uppermost one to the Amigdaloscalpellinae. Scale bars: A–E, J, K–T, Y, 1 mm; F–I, U–X, 0.5 mm.

Figure 11. Evolution of rostra and rostrolateral plate morphology, ventral side: A–D, Amigdoscalpellum truncatum (Hoek, 1883); H, Arcoscalpellum sociabile (Annandale, 1905); I–L, Arcoscalpellum michelottianum (Seguenza, 1876); M–P, Regioscalpellum regium (Thomson, 1873); Q–T, Diotascalpellum rubrum (Hoek, 1883). Rostrum in ventral (rostral) aspect (A, E, I, M, Q); rostrolatus in external (C, G, K, O, S) and internal (B, F, J, N, R) views. Basal capitulum in ventral (rostral) aspect (D, H, L, P, T). Note similarity of plesiomorphic taxa (E–T), in which the rostrolatus is broad and low, and the rostrum is trapezoidal to triangular and chunky. The rostrolatera do not contact over the midline in these taxa. Note striking morphological differences in the more derived Amigdoscalpellum truncatum (A–D), in which the rostrolatus is narrower and taller, the plates meet over the midline, and the rostrum is tiny, tall, rhomboidal, and almost completely covered by the rostrolatera. The rostral articulation only extends over half of the rostrolatus (see also Fig. 10C, H, I). Scale bars: L, P, 2 mm; B–D, F–H, J, K, N, O, T, 1 mm; A, I, M, R, S, 0.5 mm; and E, Q, 0.2 mm.

Figure 13. Carinolatera: A, B, Arcoscalpellum pedunculatum (Hoek, 1883); C, Arcoscalpellum regina (Pilsbry, 1907); D, E, Arcoscalpellum michelottianum (Seguenza, 1876); F, Arcoscalpellum quadratum (Dixon, 1850), London Clay, Eocene, Minster, Sheppey, Kent, UK (original of Withers, 1953, pl. 26, fig. 13), NHMUK In. 34504; G, H, Regioscalpellum regium (Thomson, 1873); I, J, Regioscalpellum darwini (Hoek, 1883); K, L, Diotascalpellum rubrum (Hoek, 1883); M, N, Diotascalpellum gigas (Hoek, 1883); O, P, Arcuatoscalpellum arcuatum (Darwin, 1851b), Albian, Gault Clay, Paddlesworth, Kent, NHMUK In. 61368; Q, R, Cretiscalpellum striatum (Darwin, 1851b), Campanian chalk, Norwich, UK. NHMUK IC 1198. Comparative morphology of carinolatus in out-group Cretiscalpellum and Scalpellinae to illustrate morphological variation and phylogenetic trends. Note the overall progression in morphology from the out-group (Q, R), through Arcuatoscalpellum arcuatum (P, Q), to Diotascalpellum (D. rubrum, K, L), involving differentiation of the inframedian latus surface. In the more derived R. regium (G, H), R. darwini (I, J), and R. gigas (M, N) the umbo is incurved, has migrated to a more dorsal position, and a low internal shelf has developed adjacent to the upper latus. In Arcoscalpellum (Arcoscalpellum michelottianum, D, E; Arcoscalpellum quadratum, F), the umbo is more incurved, the apex subapical, and a upper latus surface has developed (see Fig. 10 for nomenclature). Scale bars: A–I, M, N, 1 mm; K, L, O–R, 0.5 mm.