Halopteris brasiliensis Galea & Gioia Di Camillo & Maggioni & Montano & Schuchert 2018, sp. nov.

Halopteris brasiliensis Galea, sp. nov.

Figs 2H, 8; Table 5; Appendix 1

Halopteris buskii. – Migotto, 1996: 48, fig. 9F-H [non Halopteris buskii (Bale, 1884)].

Halopteris polymorpha. – Schuchert, 1997 (pro parte): 72, fig. 22F-H [non Halopteris polymorpha (Billard, 1913)].

Holotype material: MHNG-INVE-37495; Brazil, São Sebastião Channel, 6-8 m, coll. A.E. Migotto; 06.10.1987; two slides, H12/36 & 37, each containing a ca. 1.6 cm high cormoid provided with a female gonotheca.

Diagnosis: Halopteris with medium-sized plumes, reaching 3 cm high; stems simple, monosiphonic, homomerously-segmented; internodes rather short, with a lateral apophysis, a hydrotheca, and its up to 7 associated nematothecae (1 mesial, a pair of laterals, a pair of axillar, and generally 2 superiors, the latter either opposite or subopposite). Hydrocladia alternate, heteromerously-segmented; ahydrothecate internodes very short, with 1 nematotheca; hydrothecate internodes comparatively longer, with one hydrotheca and up to 5 nematothecae (1 mesial, a pair of laterals, and commonly 1, rarely 2, axillar). Female gonothecae borne on stems; large, piriform, with 2-3 long, basal nematothecae, aperture distal, wide, circular, perpendicular to long axis of theca, closed by glass-watchshaped operculum.

Etymology: Named after the country of occurrence.

Description: Colonies composed of reportedly up to 3 cm high cormoids arising from creeping, branching hydrorhiza. Stems erect, simple, monosiphonic (Fig. 2H), composed of a basal, ahydrothecate portion, and a much longer, distal part bearing both hydrothecae and hydrocladia. The former of varied length, irregularly divided into a number of segments by means of transverse nodes, bearing nematothecae arranged in two longitudinal rows; last node deeplycut and oblique. Remainder of caulus homomerouslysegmented into rather short internodes by means of oblique nodes (Fig. 8A); each internode with a hydrotheca in its proximal half, a cladial apophysis lateral to it (two opposite in proximal most internode), and up to 7 nematothecae, of which 5 are associated to the hydrotheca (1 mesial, a pair of laterals, and a pair of axillar) (Fig. 8B), and 2 (slightly displaced laterally and, thus, forming an opposite or a subopposite pair) occur distally on the internode (occasionally, only one of these is present; however, in the basalmost internodes bearing pairs of cladia, 2-3 of these occur). Hydrocladia alternate, borne on corresponding cauline apophyses; composed of a short, athecate, quadrangular segment, followed by an alternation of ahydrothecate and hydrothecate internodes resulting from a heteromerous segmentation (Fig. 8C); ahydrothecate internodes with proximal node transverse and distal node oblique; the reverse in hydrothecate internodes; first ahydrothecate internode comparatively longer than subsequent ones, and carrying a single nematotheca; ordinary ahydrothecate internodes very short and provided with single nematotheca; hydrothecate internodes, reportedly up to 7 per hydrocladium, accommodating a hydrotheca and its up to 5 associated nematothecae (1 mesial, a pair of laterals, and commonly one – rarely a pair – of axillar nematothecae) (Fig. 8D). Hydrothecae cup-shaped, rather deep, adnate for about half their height, walls slightly divergent, abaxial one imperceptibly sigmoid (concave proximally, convex below aperture), free part of adaxial one straight; aperture wide, circular, rim even (Fig. 8C). Hydranths with conical hypostome and 16-17 filiform tentacles. All nematothecae, including the axillar ones, bithalamic and movable; mesial ones short, with lower and upper chambers of nearly same depth (Fig. 8E 4), and rim of upper chamber lowered on adaxial side; lateral nematothecae borne on welldeveloped apophyses, with tall basal chamber and shallow upper chamber with sigmoid rim on adaxial side (Fig. 8E 5); whole nematotheca barely reaching hydrothecal rim (Fig. 8C); cauline (Fig. 8E 1) and cladial (Fig. 8 E 2, 3) nematothecae similar in shape to the laterals, but with lowered rim on the adaxial side of upper chamber; cauline axillar nematothecae displaced laterally and facing outwards in opposite directions (Fig. 8E 7); cladial axillar nematothecae commonly occurring singly (Fig. 8E 8), reportedly in pairs in rare instances. Gonothecae (only female known) borne on both cauli and cladia, given off laterally from below the hydrothecal bases; large, piriform, with 2-3 long, basal nematothecae, and a broad, circular aperture with thickened rim, perpendicular to long axis of the theca (Fig. 8F), and closed by glass-watch-shaped operculum. In life, coenosarc yellowish, hydranths white. Cnidome: at least pseudostenoteles [(18.0-21.5) × (7.5-9.0) μm] and microbasic mastigophores [(6.0-7.0) × ca. 2.0 μm] reported to date.

Dimensions: See Table 5.

Remarks: The description given above is based on the holotype, although some additional data, such as the cnidome composition, are taken from Migotto (1996, as H. buskii).

Through the presence of pairs of cauline axillar nematothecae and the heteromerous segmentation of its cladia, H. brasiliensis comes close to a number of congeners, viz. H. australis sp. nov., H. liechtensternii, H. sibogae, and H. vervoorti. Halopteris australis is immediately distinguished through it distinctly sinuated hydrothecal margin. Halopteris liechtensternii, when fertile, has comparatively longer and more tubular female gonothecae. Halopteris sibogae has distinctive, exceedingly long nematothecae (Fig. 2C). Halopteris vervoorti forms comparatively shorter stems (compare Fig. 2 C-E and 2H), their cauli and cladia are thinner (compare Fig. 5A, B, M and 8A), and their cauline hydrothecae are placed in the lower halves of the corresponding internodes, leaving enough place for 1-2 superior nematothecae, arranged in one row, to be confined to their distal halves (Fig. 5C). Additional differences to other congeners are summarized in Appendix 1.

Distribution: Only known from Brazil (Migotto, 1996).