Arcoscalpellum mamillatum ( Aurivillius, 1898 ) Young, 2001

Young, Paulo S., 2001, Deep-sea Cirripedia Thoracica (Crustacea) from the northeastern Atlantic collected by French expeditions, Zoosystema 23 (4), pp. 705-756 : 732-738

Arcoscalpellum mamillatum ( Aurivillius, 1898) , n. comb.

( Figs 19-22 )

Scalpellum mamillatum Aurivillius, 1898: 191 . — Gruvel 1905: 69; 1920: 21, pl. 5, figs 19-21. — Nilsson- Cantell 1955: 218. — Belloc 1959: 3. — Zevina 1976: 1155.

Amigdoscalpellum mamillatum – Zevina 1978: 1349.

Amygdoscalpellum [sic] mamillatum – Zevina 1981: 269 (part, not fig. 202 (= Amigdoscalpellum semisculptum [Pilsbry, 1907])).

MATERIALEXAMINED. — ECOFER 1, stn CP 01, 44°46.20’N, 02°38.15’W, 3017 m, 1 specimen, tl (cl) 25.4 (19.0) mm (MNHN Ci 2871).

DESCRIPTION

Capitulum ( Fig. 19A ) oval, flattened, length almost twice width, occludent and carinal margins convex and similar. Plates with strong radial ribs, except on carinal part of tergum; with spaced, thin growth lines. Cuticle thin, not pilose.

Tergum ( Fig. 19A ) with its surface area greater than scutum; inconspicuous apicobasal ridge. Basal margin straight. Carinal margin slightly convex, with lateral thickening near apex of carina. Occludent margin convex. Apex slightly curved toward carina.

Scutum ( Fig. 19A ) with conspicuous apicobasal ridge, separating two surfaces; height more than twice greatest width. Basal margin straight. Tergal margin slightly concave, presenting a lid. Occludent margin nearly straight, only distally convex. Lateral margin convex except for upper concavity to accept apex of upper-latus. Apex curved, superimposed on tergum.

Carina ( Fig. 19A, B ) arching more conspicuously at apex, wider at upper portion, with umbo slightly subapical. Tectum flat, bordered by lateral ridges; basal margin nearly straight.

Upper-latus ( Fig. 19A ) pentagonal with apex curved toward scutum, umbo subapical, projecting. Scutal margin concave; other margins straight.

Carino-latus ( Fig. 19A, B ) nearly pentagonal, higher than wide, with umbo at carinal base, not projecting backward. Carino-latera interdigitating with one another below carina.

Inframedian-latus ( Fig. 19A ) triangular, with umbo curved toward scutum, with two apical wings projecting toward carinal margin.

Rostro-latus ( Fig. 19A, C ) trapezoidal, wider than high, width almost two times height, with an apico-basal ridge. Lower margin two-thirds length of upper margin.

Rostrum ( Fig. 19C ) small, reduced to narrow slip between rostro-latera.

Peduncle ( Fig. 19A ) one-third length of capitulum, covered by large scales projecting outward. Scale whorl eight-plate pattern: rl-cl; sr-l-sc.

Labrum ( Fig. 20A ) bullate, with series of about 47 denticles. Palp ( Fig. 20A, B ) short, acuminate with few simple setae. Mandible ( Fig. 20C, D ) with three teeth or with second and third reduced; lower angle denticulate. Maxilla I ( Fig. 20E ) with anterior border having medial notch, and two large and 10 smaller unpaired spines. Maxilla II ( Fig. 20F ) rounded, globose; covered by numerous simple setae; papilla of maxillary gland pronounced.

Cirrus I ( Fig. 21A ) with unequal rami, anterior ramus three-quarter length of posterior ramus; former with protuberant articles. Cirrus II with equal rami but shorter than posterior cirri. Cirri III to VI with equal, long rami. Cirri I to III with several long, simple setae on anterior margin, lateral face and posterior margin, which decreases progressively in size and number toward posterior rami ( Fig. 21 B-D). Larger setae of median article of cirri II, III and IV, 2.5, 3.3, 1.8 times length of article, respectively ( Fig. 21 B-D). Median article of cirrus VI less than two times longer than wide, three pairs of simple setae unequal in length and few fine setulae on anterior margin; unpaired simple setae on lateral face; intercalated setae on posterior margin and one or two setae on posterior angle. Number of articles of cirri I-VI and caudal appendage is presented in Table 5.

Caudal appendage ( Fig. 21E ), with six to seven articles, shorter than length of coxopodite of cirrus VI; articles with few, small setae on distal margins, one or two long setae on anterior margin, and cluster of simple setae on apex. Penis absent.

REMARKS

Gruvel (1920) considered Scalpellum semisculptum Pilsbry, 1907 to be synonymous with Arcoscalpellum mamillatum n. comb. This synonymy was considered doubtful by Broch (1953: 7) and Nilsson-Cantell (1955: 218) but accepted by Zevina (1981: 269) in her revision of the scalpellid. This species is transferred to Amigdoscalpellum because the apex of the inframedian-latus does not reach the upper margin of the lower row of plates. Herein the synonymy between these species is not considered and both species are placed in different genera: Amigdoscalpellum semisculptum and Arcoscalpellum mamillatum n. comb. The latter species has a large inframedian-latus, with its apex reaching the upper margin of the rostro- and carino-latus. Table 6 presents the differences between both species justifying their separation.

60°

40°

20°

80° 60° 40° 20° 0°

The distribution of Arcoscalpellum mamillatum n. comb. is therefore restricted by the original samples (Azores region) and the new record (Bay of Biscay). Amigdoscalpellum semisculptum is recorded from the Gulf of Mexico and west of Iceland ( Fig. 22 ) ( Broch [1953] cited Scalpellum semisculptum as collected at stn10 but when he figured it on map 12 he marked in the stn 25, I considered the citation of stn 10 [West of Iceland] as the correct one).

Arcoscalpellum atlanticum (Gruvel, 1900) n. comb. ( Figs 23 ; 24 )

Scalpellum atlanticum Gruvel, 1900a: 190 ; 1902d: 74, pl. 2, figs 17, 18; 1905: 68, fig. 76; 1920: 26, pl. 7, fig. 5. — Hoek 1914: 4. — Belloc 1959: 3.

Teloscalpellum atlanticum – Zevina 1978: 1350; 1981: 377, fig. 294.

Arcoscalpellum tritonis – Young 1998a: 19, figs 15, 16; 1998b: 36, fig. 1 [non Arcoscalpellum tritonis ( Hoek, 1883) ].

MATERIALEXAMINED. — SEAMOUNT 2, stn DW 185, 31°25.46’N, 28°51.85’W, 1250 m to 31°25.19’N, 28°51.89’W, 950 m, 1 specimen, tl (cl) 8.3 (6.5) mm (MNHN Ci 2872). — Stn DW 200, 31°19.07’N, 28°36.01’W, 1060 m to 31°19.27’N, 28°35.92’W, 1100 m, 1 specimen, tl (cl) 11.4 (8.7) mm (MNHN Ci 2873). — Stn DW 277, 33°59.92’N, 28°20.56’W, 1000 m to 33°59.64’N, 28°20.81’W, 945 m, 2 specimens, tl (cl) 11.9 (9.4) to 12.8 (10.3) mm (MNHN Ci 2874, MNRJ 13913 ). — Stn DW 278, 33°57.77’N, 28°22.40’W, 890 m to 33°57.47’N, 28°22.48’W, 925 m, 3 specimens, tl (cl) 5.6 (4.9) to 9.6 (8.3) mm (MNHN Ci 2875; MNRJ 13914 ) .

REMARKS

The specimens examined ( Fig. 23 ) agree with the description of Gruvel (1902d: 74) including the general eight-plate pattern of the peduncle. I only observed a variation in the roof of the carina. It

C

varied from flat with conspicuous high bordering ribs in smaller specimens to flat with very low inconspicuous bordering ribs in larger ones.

The specimens I identified as Arcoscalpellum tritonis ( Hoek, 1883) from Portugal, Morocco and Azores should be placed in A. atlanticum (Gruvel, 1900) n. comb. ( Young 1998a: 19, b: 36). I originally tought A. tritonis may be a junior synonym but a few character differences and its geographic distribution ( Fig. 24 ) suggests maintaining both species as valid. A. tritonis has the rostro-latus more trapezoidal, and the inframedian-latus with a curved apex, more scales on the peduncle and it does not have a rostrum.

Figures

FIG. 19. — Arcoscalpellum mamillatum (Aurivillius, 1898), ECOFER 1, stn CP 01; A, left lateral view; B, carinal view; C, rostral view. Scale bars: A, 5 mm; B, C, 3 mm.

FIG. 20. — Arcoscalpellum mamillatum (Aurivillius, 1898), ECOFER 1, stn CP 01; A, labrum and palp; B, palp; C-D, mandibles; E, maxilla I; F, maxilla II. Abbreviation: mg, maxillary gland. Scale bars: 0.3 cm.

FIG. 21. — Arcoscalpellum mamillatum (Aurivillius, 1898), ECOFER 1, stn CP 01; A, cirrus I; B-D, detail of the 7th article of posterior ramus of cirrus II, 9th article of posterior ramus of cirrus III, and 13th article of posterior ramus of cirrus VI, respectively; E, caudal appendage. Abbreviations: a, anterior ramus; C I, cirrus I; C II, cirrus II; C III, cirrus III; C VI, cirrus VI; ca, caudal appendage; p, posterior ramus. Scale bars: A, 1 cm; B-E, 0.5 cm.

FIG. 22. — Geographic distribution of Arcoscalpellum mamillatum (Aurivillius, 1898) (circles) and Amigdoscalpellum semisculptum (Pilsbry, 1907) (triangles).

FIG. 23. — Arcoscalpellum atlanticum (Gruvel, 1900) n. comb., SEAMOUNT 2, stn DW 277; A, right lateral view; B, carinal view; C, rostral view. Scale bars: 2 mm.

FIG. 24. — Geographic distribution of Arcoscalpellum atlanticum (Gruvel, 1900) n. comb. (triangles) and Arcoscalpellum tritonis (Hoek, 1883) (circles).