Amigdoscalpellum, ZEVINA, 1978

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 : 300

GENUS AMIGDOSCALPELLUM ZEVINA, 1978 B

FIGURES 1A–C , 3E–G , 6A–E , 7U–Y , 8B, F, J , 11A–D , 12Q–T

Type species

Arcoscalpellum manum Zevina, 1973 , by subsequent designation Zevina, 1978b.

Diagnosis

Sculpture of strong, radially arranged, rounded raised ridges on all plates except carina; carinolatera articulate across midline by means of zig-zagging, alternating ridges that diverge from umbones. Umbones of carinolatera central to subcentral, close to base of carina, not prominent. Inframedian latus narrow, triangular, more rarely elongate, rectangular, umbo apical, often not extending to top of carinolatus and rostrolatus. Rostrum small, less than half the height of the rostrolatus, narrow, rounded oval rhombic outline.

Included species

Scalpellum vitreum Hoek, 1883 , Scalpellum rigidum Aurivillius, 1898 , Scalpellum mamillatum Aurivillius, 1898 , Arcoscalpellum truncatum Hoek, 1883 , Scalpellum elegans Hoek, 1907 , Scalpellum formosum Hoek, 1907 , Scalpellum trapezoideum Hoek, 1907 , Scalpellum semisculptum Pilsbry, 1907 , Scalpellum aurivilli Pilsbry, 1907 , Scalpellum galapaganum Pilsbry, 1907 , Scalpellum rigidum Aurivillius, 1898 , Scalpellum sculptum Hoek, 1907 , Scalpellum (Arcoscalpellum) constellatum Withers, 1935 , Arcoscalpellum pertosum Foster, 1978 , Scalpellum (Arcoscalpellum) bellulum Withers, 1935 (Cretaceous, Campanian, UK), and Arcoscalpellum turinensis Withers, 1953 (Miocene, Helvetian, Turin, Italy). Young (2007: 59–60) provided a useful discussion of extant species of Amigdoscalpellum , and suggested that extensive synonymy of taxa was a likely possibility.

Remarks

Thus defined, Amigdaloscalpellum appears to be a monophyletic entity. The distinctive radial sculpture is also present, albeit in a weaker and more restrict- ed form, on some fully grown individuals of a few species of Catherinum (e.g. Ca. australicum , Ca. recurvitergum , and Ca. striolatum ; see Young, 1998). These can, however, always be distinguished on the basis of the morphology of the inframedian latus and the overlap of the scutum by the upper latus. Note that the genus as here defined also includes some taxa traditionally referred to Arcoscalpellum (such as Arcoscalpellum truncatum ), which fall naturally in Amigdoscalpellum .

Figures

Figure 1. Morphology and nomenclature of the scalpellid capitulum, and constituent carina, tergum, and scutum. A–C, I, Amigdoscalpellum truncatum (Hoek, 1883): A, dorsal (carinal) view; B, lateral view; and C, ventral (rostral) view. D, E, carina of Catherinum striolatum (G.O. Sars, 1877) in dorsal and lateral aspect. F, G, scutum of Weltnerium stroemii (M. Sars, 1859) in internal and external views, respectively. H, Amigdoscalpellum rigidum (Aurivillius, 1898), tergum in external aspect. For abbreviations, see Table 2. For details of localities etc., see Table 1. Scale bars: A–C, 5 mm; D–I, 1 mm.

Figure 3. Lateral aspects of Amigdoscalpellinae: A, Catherinum striolatum (G.O. Sars, 1877); B, Catherinum recurvitergum (Gruvel, 1900); C, Catherinum novaezelandiae (Hoek, 1883). D, Weltnerium nymphocola (Hoek, 1883); E, Amigdaloscalpellum rigidum (Aurivillius, 1898); F, Amigdaloscalpellum truncatum (Hoek, 1883); G, Amigdaloscalpellum sculptum (Hoek, 1907) H, Weltnerium stroemii (M. Sars, 1859). See Table 1 for localities. 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 7. Evolution of lateral plate morphology, dorsal side: A–E, Weltnerium stroemii (M. Sars, 1859); F–J, Weltnerium nymphocola (Hoek, 1883); K–O, Catherinum novazelandiae (Hoek, 1883); P–T, Catherinum striolatum (G.O. Sars, 1877); U–Y, Amigdoscalpellum rigidum (Aurivillius, 1898). 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); dorsal (carinal) view of basal capitulum (D, I, N, S, X); enlarged lateral view of basal capitulum (E, J, O, T, Y). Note the changes in the nature of the articulation between the carinolatera of a pair (interpenetrant, X; opposed double articulation, D, I, N, S) and those in the shape of the inframedian latus (triangular, W; waisted hourglass, M, R; pentagonal, C, H). See Table 1 for details of localities. Scale bars: A–C, F–H, M, P-R, U–V, 0.5 mm; D, E, I, J, N, O, S, T, X, Y, 1 mm.

Figure 8. Scalpellid scuta and terga. Scuta: A, E, Arcoscalpellum sociabile (Annandale, 1905); B, F, Amigdoscalpellum rigidum (Aurivillius, 1898); C, G, Catherinum hispidum (G.O. Sars, 1890); D, H, Weltnerium stroemii M. Sars, 1859). Terga: I, Arcoscalpellum michelottianum (Seguenza, 1876); J, Amigdoscalpellum rigidum; K, Catherinum hispidum; L, Weltnerium stroemii. See Table 1 for details of localities. Note the overall progression of morphological change from left to right in the shape of the scutum, with the basal–occludent angle becoming more acute, and the basal–upper latus angle more obtuse, leading to a more trapezoidal outline. Additionally, a small tergal surface develops, and the umbo becomes incurved, and the dwarf male receptacles become larger and better defined. The terga change from an oval– rhombic outline (I) to a right triangular one (J–L), the ventral margin has developed a narrow supracarinal surface (scs), with an inflexion where the tip of the carina rests against the carinal margin. See Table 1 for details of localities. Scale bars: K, 2 mm; A, E, F, J, M, N, 1 mm; B–I, L, 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 12. Evolution of rostra and rostrolatera plate morphology, ventral side: A–D, Weltnerium stroemii (G.O. Sars, 1859); E–H, Weltnerium nymphocola (Hoek, 1883); I–L, Catherinum novazelandiae (Hoek, 1883); M–P, Catherinum striolatum (G.O. Sars, 1877); Q–T, Amigdoscalpellum rigidum (Aurivillius, 1898), rostrum in ventral rostral aspect (A, E, I, M, Q); rostrolatus in external (B, F, J, N, R) and internal (C, G, K, O, S) views. Basal capitulum in ventral (rostral) aspect (D, H, L, P, T). The rostrum is tiny, with only a small external face (I, M, Q) in more basal taxa. In the most derived taxa, the central ridge has an external surface over the height of the plate (A, B). Scale bars: A–D, F–H, J–L, N–P, R–T, 0.5 mm; E, I, M, Q, 0.2 mm.