Scalpellum carentanensis, Carriol, René-Pierre, 2013

Carriol, René-Pierre, 2013, Two new species of scalpelliform barnacles (Cirripedia: Thoracica) from the Plio-Pleistocene of Cotentin, northwest France, Zootaxa 3641 (1), pp. 21-30 : 22-24

Scalpellum carentanensis sp. nov.

Fig. 1 A–G

Diagnosis. Carina with tectum rounded, having umbo removed from apex. Terga triangular with apico-basal fold, without outward extension; raised part on apical area of inner surface marked by wide growth lines, cut by groove. Scutum with ridge extending from umbo to tergo-lateral angle, lacking apico-basal ridge, line formed by convergence of growth zones present. Length of upper lateral exceeding width by approximately 1.25 times, umbo situated one-fifth of plate length from apex.

Etymology. Named after the Carentan Basin, Manche (northwest France).

Occurrence. Piacenzian to Gelasian from ‘Champeaux’ (co-ordinates: x = 335.84; y = 1172.9) in the Marchésieux district of the Département de la Manche.

Material examined. Inventory, and designation of the type material, see Appendix 1

MEASUREMENTS.

Plate Height (mm) Width (mm) Holotype

MNHN.F.45800 tergum (broken) 2.0 (apex to carino-scutal angle) 0.95 (scuto-occludent angle to

carinal margin) Paratypes

MNHN.F.A45801 scutum 5.3 2.3 MNHN.F.A45802 scutum 2.8 1.5 MNHN.F.A45803 carina 3.5

MNHN.F.A45804 carina 2.8

MNHN.F.A45805 carina 3.2

MNHN.F.A45806 upper lateral 1.3 1.0

Description. Tergum triangular, apicobasal fold situated very close to carinal margin, where growth lines turn abruptly upwards; umbo apical. Carinal margin slightly sinuous. Occludent margin slightly convex. Scutal margin straight. Carinal margin longest; scutal and carinal margins of comparable length. Inner surface with apical part of plate along upper carinal margin and occludent margin raised, marked with growth lines meeting to form rounded angle situated at one-third of plate length below apex; groove cutting raised wide part along upper carinal margin.

Scutum trapezoidal, umbo placed on occludent margin. Occludent margin straight, hollowed out above umbo, terminating in narrow, rounded apex. Tergal margin straight. Lateral margin concave beneath projecting tergolateral angle, strongly convex in lower part. Basal margin straight to slightly convex. Ridge extending between projecting tergo-lateral angle and umbo. Apico-basal ridge absent, line formed by convergence of growth zones extending down from umbo to lateral-basal angle. Inner surface with depression on occludent margin deep, above deep, wide adductor muscle pit.

Carina moderately bowed inwards, angularly bent with umbo removed from apex. Basal margin convex. Tectum rounded transversely, parietes somewhat concave, intraparietes inclined outwards.

Upper lateral pentagonal, length about 1.25 times width, umbo situated about one-fifth plate length from apex. Scutal and tergal margins forming angle of about 80°. Scutal margin weakly concave, shorter than sinuous tergal margin. Basal margin with scutal side almost straight, longer than concave tergal side.

Affinities. Withers (1953) lists two species of Scalpellum from the Pliocene in Europe: S. magnum Darwin, 1851 from the Piacenzian (late Pliocene) Coralline Crag of southeast England and S. molinianum Seguenza, 1876 from the Piacenzian of Italy. Scalpellum magnum , or a closely related form, has recently been noted from the Kattendijk Formation (early Pliocene, Zanclean) of the Antwerp area, northwest Belgium (Marquet et al. 2009). Since 1953, no other species of Scalpellum has been recorded from the Pliocene.

Scalpellum carentanensis sp. nov. differs from S. magnum in that the carina of the latter is constricted in the umbonal region, the tergum has a thick occludent margin, the exterior surface of the scutum has four ridges, and the upper lateral has a centrally placed umbo. The new species is distinguished from S. molinianum in that the latter has a carina with a flat tectum, bordered on each side by a low, usually strong ridge; the tergum has an outward extension, the exterior of the scutum has four ridges, and the umbo of the upper lateral is situated about one third the plate length from the apex.

Figures

FIGURE 1. Scalpellum carentanensis sp. nov. A 1 – 2: paratype MNHN. F. A 45801, internal and external sides of right scutum; B: paratype MNHN. F. A 45806, external side of upper lateral; C 1 – 2: holotype MNHN. F. A 45800, internal and external sides of left tergum; D 1 – 2: paratype MNHN. F. A 45802, internal and external sides of right scutum; E: paratype MNHN. F. A 45803, lateral side of carina; F: paratype MNHN. F. A 45805, carina; G: paratype MNHN. F. A 45804, carina. Scale bars represent 1 mm.