Scutoplites hamartia, Reverter-Gil & Souto & Berning, 2025

Reverter-Gil, Oscar, Souto, Javier & Berning, Björn, 2025, Unexpected diversity in North Atlantic deep waters hidden under Scrupocellaria marsupiata (Bryozoa: Cheilostomatida), Zootaxa 5618 (3), pp. 326-350 : 334

Scutoplites hamartia sp. nov.

( Fig. 5 ; Table 1 )

Scrupocellaria marsupiata : d’Hondt 1975: 556 (part), not figs 14–16.

Material examined. Holotype: MNHN-IB-2008-7441 : Biaçores stn. 64, 38º43’N, 28º29’W, 1200–1240 m, 14 Oct. 1971, several small fragments of a single colony, dry ( Fig. 5 A, B, E ) . Paratype: MNHN-IB-2008-7420 : Biaçores stn. 54A, 38º12’N, 28º15’W, 1810 m, 13 Oct. 1971, proximal part of colony with rhizoids, dry ( Fig. 5 C, D ).

Etymology. hamartia , noun from ancient Greek ἁμαρτία (error), as the material here assigned to this new species was originally misidentified as S. marsupiata .

Description. Colony erect, dichotomously branching, attached to the substrate by rhizoids that are produced from a small pore near the proximal end on the abfrontal side of some autozooids, densely intertwined to form a stalk. Branches formed by two series of alternating autozooids opening on one side only. Branching points composed of a single proximomedian autozooid and two distolateral ones. Autozooids elongate, narrower and tubular proximally, with the distal half turned outwards alternatingly to right or to left. Skeletal surface smooth, autozooids separated by a distinct groove, forming a zigzag line on the abfrontal side. Distal half of autozooid occupied by an extensive oval membranous area, covered proximally by a large, convex, flabelliform scutum, elongate oval, longer than wide. Main axis of scutum originating from a broad and strongly recurved base near the inner distal autozooid margin just proximolateral to orifice and directed proximally. Scutum covering the entire frontal area, digit-like prolongations present all around the main axis, usually branching once, merging with the circum-opesial gymnocyst, leaving 21–27 slit-like fissures of variable length between them, long fissures generally alternating with short ones. Distal edge of scutum projecting as a straight lip that delimits the small opercular area, oral margin slightly raised, as long as wide, somewhat asymmetrical and displaced towards the outer autozooid marging. Operculum thickly sclerotised. Outer distal angle of autozooids with one spine, presumably strong but broken in the examined material. Inner distal angle with one spine, inconstant, usually broken. Median autozooids at branching points with only one outer spine.

Adventitious avicularia of two kinds: one situated distolateral to orifice but displaced basally and generally difficult to see in frontal view, with the triangular mandible directed outwards; another small avicularium on a raised cystid just proximally to scutum, its triangular mandible directed upwards. Mandibles in both avicularia hinged on inconspicuous condyles.

Ovicell lacking in the material examined. An ancestrula was not observed.

Remarks. The description of S. hamartia sp. nov. is based on several fragments, the largest of them comprising 12 autozooids with two branching points, but all of them lacking ovicells. Therefore, the description cannot be complete. However, the remaining characters are significant enough to differentiate this species from the others treated in the present work.

Scutoplites marsupiatus n. comb. has shorter autozooids (c. 0.5 mm), a shorter scutum that is nearly as long as wide and with fewer fissures (c. 15), as well as with a stout spine on its base; the lateral avicularium is large, positioned laterally to the orifice and clearly visible in frontal view; and finally, the orifice is as long as wide. In S. clausus n. comb. the autozooids are longer and narrower (1.000 x 0.222 mm), there are fewer fissures around the scutum (7–9) and none on the inner margin; up to three spines are present on the outer distolateral edge and a stout spine is present near the base of the scutum. Scutoplites saojorgensis n. comb. shares with S. hamartia sp. nov. the orifice displaced towards the outer autozooid margin and the high number of fissures in the scutum, which, however, has a completely different appearance. Moreover, in S. saojorgensis n. comb. most of the autozooids lack spines, the scutum is wider than long, and the lateral avicularium is clearly visible in frontal view. Finally, in S. reverteri n. comb. the autozooids are clearly shorter, the scutum less developed, the lateral avicularium is visible in frontal view, and autozooids bear two lateral and four distal, stout, pointed spines.

The material here described as S. hamartia sp. nov. was originally identified by d’Hondt (1975) as Scrupocellaria marsupiata but, as noted above, several species were combined under this name in that work. The specimens imaged by d’Hondt (1975: figs 14–16), without any further comments, do not belong to the present species because they show a smaller scutum with few fissures and autozooids devoid of spines, except for the median one in a branching point. This material mostly resembles S. virgulus sp. nov. (see below).

At present, S. hamartia sp. nov. is known only from the central Azores around Ilha do Pico, at depths between 1200 m and 1810 m.

Figures

FIGURE 5. Scutoplites hamartia sp. nov. A, B. Close-up of branch bifurcations; note that the central autozooids of the dichotomies are mirror images in both photos, while the two distal autozooids look exactly the same (MNHN-IB-2008-7441, holotype). C. Dichotomy in basal view (MNHN-IB-2008-7420, paratype). D. Same, close-up of a autozooid with scutum partially broken. E. Detail of two autozooids (MNHN-IB-2008-7441, holotype).