Scutoplites, Reverter-Gil & Souto & Berning, 2025

Genus Scutoplites n. gen.

Type species. Scrupocellaria marsupiata Jullien, 1882

Etymology. Name compound of ‘scutum’, alluding to the characteristic scutum covering the frontal membrane like a well-fitting lid, and ‘ Notoplites ’, a very similar genus in which several of the species discussed here were included until now. Gender masculine.

Diagnosis. Colony erect, dichotomously branching, anchored to the substrate by rhizoids that descend along the main axis. Branches articulated, biseriate, with alternating autozooids. Branching pattern type 15 ( Harmer 1923). Autozooids elongate, narrower proximally, with an oval frontal membrane placed distally. Inarticulate spines usually present on the distal margin of autozooids. A flabelliform scutum covering the frontal membrane like a well-fitting lid, the proximolateral edge merging with the circum-opesial gymnocyst, scutum margin here straight or fimbriated. Distal opercular area restricted by the arcuate opesial margin, its proximal edge defined by the straight distal part of the scutum. Operculum thickly sclerotised. Avicularia of two types: a small one, sessile, present distolaterally, in the form of a triangular prominence on the side of the autozooid, not always seen in frontal view, with the triangular mandible pointing outwards; a small frontal avicularium located just proximal to the scutum, situated on a small prominence and provided with a triangular mandible directed proximally. Ovicell hyperstomial, large, prominent, not closed by the operculum, with a small frontal fenestra in the ectooecium. Ancestrula not known.

Remarks. Several of the species of Scutoplites n. gen. discussed here, including the type species, were until now classified in the genus Notoplites . The main characters that differentiate Scutoplites from Notoplites species are: the well-developed scutum that covers the frontal membrane like a well-fitting lid, with the proximal and outer-lateral margins merged with the opesial rim, leaving the operculum uncovered. This character is apparently absent in Notoplites species. In most of the species the scutum is distinctly smaller and of variable shape, exposing a relatively large area of the frontal membrane, whereby it may even be absent in other species. Secondly, in the Scutoplites species the scutum has a fimbriated edge, with branches separated by a variable number (6–27) of more or less narrow fissures of variable length. Thirdly, all the species in Scutoplites have a small, sessile avicularium in the distolateral corner of each autozooid, which may not always be visible in frontal view, as well as a small frontal avicularium located just proximal to the scutum in many of the autozooids. In contrast, according to the original description ( Harmer 1923), in Notoplites frontal and marginal avicularia may be present or absent and additional basal avicularia, approaching a vibraculoid form, are typically present and usually confined to the neighbourhood of the axil. Jullien (1882) mentioned a single basal (i.e. abfrontal) vibraculum behind the lateral avicularium in Scrupocellaria marsupiata , but this was not observed in the redescription of the species ( Souto et al. 2011). Similarly, Busk (1884) mentioned a minute avicularium as being positioned in the distal abfrontal autozooid in Menipea clausa Busk, 1884 , and R. Kirkpatrick (in Waters 1888) also noted the presence of vibracula in several autozooids, but again these were not found during the redescription of the species ( Souto et al. 2011). Perhaps these authors incorrectly interpreted the lateral avicularium, which in this species is displaced basally, as a basal vibraculum. The only northern Atlantic Notoplites species with an unequivocal abfrontal avicularium seems to be Notoplites bilobus ( Busk, 1884) from the Azores (see Berning & Spencer Jones 2023). None of the species we here assign to Scutoplites were observed to form an abfrontal/basal avicularium.

In addition to the type species, Scutoplites n. gen. includes the following species: M. clausa , Notoplites saojorgensis Berning, 2013 , Notoplites reverteri Souto, 2019 , Scutoplites hamartia sp. nov., Scutoplites virgulus sp. nov., Scutoplites azorensis sp. nov., Scutoplites burocraticus sp. nov. and Scutoplites batmani sp. nov.

Key to the species of Scutoplites n. gen.

1 Semielliptical scutum with fissures arranged obliquely towards the proximal external side ( Fig. 10 View FIGURE 10 )............................................................................................ S. batmani sp. nov. (3730–4960 m)

- Scutum diversely shaped, with radial fissures............................................................... 2

2 Six stout, pointed, distal spikes. Scutum with many digital branch prolongations with wide slit-like indentations between them. Frontal avicularium present only in the median autozooid in the branching point ( Fig. 4 View FIGURE 4 )..... S. reverteri n. comb. (1067 m)

- Fewer distal spines or absent. Scutum diversely shaped. Frontal avicularium frequent............................... 3

3 Lateral avicularia large, prominent, with mandible directed outwards............................................ 4

- Lateral avicularia small, sometimes not visible in frontal view, with mandible directed proximally and outwards......... 5

4 Autozooids small (0.527 x 0.263). Scutum and operculum roughly as long as wide; two outer spines, plus one on the base of the scutum, inconstant; ovicell almost twice as long as wide ( Fig. 1 View FIGURE 1 ).................. S. marsupiatus View in CoL n. comb. (2018 m)

- Autozooids large (0.923 x 0.331). Scutum and operculum wider than long; one spine on the base of the scutum, inconstant, plus another one in the distal outer angle, frequently missing; ovicell only slightly longer than wide, with a small triangular frontal fenestra ( Fig. 3 View FIGURE 3 )....................................................... S. saojorgensis n. comb. (830–1280 m)

5 Few radial fissures in the scutum (6–13)................................................................... 6

- Many radial fissures in the scutum (16–27)................................................................ 8

6 Branches with an evident zigzag outline; radial fissures all around the scutum ( Fig. 9 View FIGURE 9 )..... S. burocraticus sp. nov. (2757 m)

- Branches straight; radial fissures absent on the inner side of the scutum.......................................... 7

7 Scutum clearly longer than wide, with shorter fissures; up to three outer distal spines; lateral avicularia not visible in frontal view ( Fig. 2 View FIGURE 2 )............................................................ S. clausus n. comb. (1940–3063 m)

- Scutum slightly longer than wide, with longer fissures; one single outer distal spine, inconstant; lateral avicularia hardly visible in frontal view ( Figs 6 View FIGURE 6 , 7 View FIGURE 7 )................................................... S. virgulus sp. nov. (3730–4270 m)

8 Two or three stout outer spines; fewer (16–21) and shorter fissures leaving a wide central imperforate area in the scutum ( Fig. 8 View FIGURE 8 )......................................................................... S. azorensis sp. nov. (1230 m)

- One stout outer spine; more (21–27) and longer fissures, long fissures generally alternate with short ones ( Fig. 5 View FIGURE 5 )................................................................................. S. hamartia sp. nov. (1200–1810 m)