Macellicephala macintoshi Neal & Brasier & Wiklund 2018, sp. nov.

Macellicephala macintoshi sp. nov.

(Figure 2B, Figures 5, 6; Table 2.)

Polynoe (Macellicephala) mirabilis in Mclntosh (1905): 59.

Macellicephala mirabilis in Pettibone (1976): 10, p. 12: Fig. 3a–e.

Material examined: Holotype and paratype, both specimens of McIntosh (1905), originally BMNH 1924: 7: 21: 12, South Africa (Cape of Good Hope), 540–900 m depth. Holotype retains original designation BMNH 1924: 7: 21: 12, paratype newly designated as NHMUK. 2018.25345.

Description (based on holotype). Holotype 25 mm long, 6.5 mm wide including parapodia and 2 mm wide excluding parapodia; with 18 segments (segment 1 = tentacular segment); body dorsoventrally flattened, tapering anteriorly and posteriorly. Colour in alcohol deep purple dorsally (Fig. 5A) and yellow ventrally, prostomium without pigmentation, only ceratophore of median antenna with blotches of purple pigment.

Prostomium bilobed with deep anterior notch; prostomial lobes moderately extended with tapering to somewhat angular anterior margin (Fig. 2B, Fig. 5B). Frontal filaments short, slender, extending from tapering lobes, medially inserted (Fig. 2B, Fig. 5B). Eyes absent. Facial tubercle large, with three distinct, inflated pads (Fig. 2B, Fig. 5D). Ceratophore of median antenna prominent, but relatively short (much shorter than prostomial lobes), cylindrical, inserted posteromedially on prostomium (near the base of anterior notch); style of median antenna missing (Fig. 2B, Fig. 5B). Palps smooth, distally tapering, relatively short (extending to segment 3).

Tentaculophores prominent, of equal size, cylindrical, inserted laterally to prostomium, achaetous; styles missing (Fig. 2B, Fig. 5B). Pharynx not observed. Second segment with elytrophores, biramous parapodia, chaetae and ventral cirri.

Nine pairs of prominent, bulbous elytrophores, on segments 2, 4, 5, 7, 9, 11, 13, 15 and 17; all elytra missing. Dorsal ridges absent.

Parapodia biramous. Notopodia reduced to elongate acicular lobe (Fig. 6A), tip of notoacicula not penetrating epidermis. Neuropodia large (Fig. 6A), subtriangular tapering to elongate acicular lobe, tip of neuroacicula not penetrating epidermis. Cirrigerous segments with prominent bulbous dorsal cirrophores, inserted basally on notopodia; all dorsal styles missing; small but distinct conical dorsal tubercles present (Fig. 5C). Ventral cirri smooth, tapering, present from segment 2; inserted basally on segment 2, where long (exceeding length of associated neuropodia lobe) inserted medially on subsequent segments, where extremely short.

Notochaetae stouter than neurochaetae; some very long, few (about 6 present per ramus) often entirely broken off, smooth, with blunt tips; copper-coloured (Fig. 6B). Neurochaetae numerous and dense (Fig. 6C–G), upper and lower neurochaetae shorter and slender (Fig. 6G), others very long; all flattened, with extremely faint serration on both margins, tapering into pointed tip (Fig. 6C–E).

Two distinct white lines running through ventral side of neuropodia and ventrum of each segment (except for tentacular segment) very prominent (Fig. 5E). Prominent globular nephridial papillae on ventrum of segments 10, 11 and 12 (Fig. 5E), inconspicuous in other segments, present from segment 5. Reduced parapodia of segment 18 lateral to pygidium, consisting of notopodia only. Pygidium rounded. Anal cirri not observed.

……continued on the next page

? Information not given in the description, neither it can be estimated from the drawings or it is stated as not observed due to poor condition of the specimen

n/a - character not applicable

§ - re-description given by Pettibone (1976) is based on several specimens, which likely represent different species, revision is needed

* Wu and Wang (1987) stated that facial tubercule is absent in M. australis, however large trilobed facial tubercule can be clearly seen depicted in their drawing (p.26, Fig. 9)

# In original description by McIntosh (1885) and accompanying drawing, the frontal filaments were clearly present in this specimen, however by the time of Pettibone's re-description as well as our recent examination of this specimen, these filaments must have fallen off as they are no longer present. Based on the drawing of McIntosh, these filaments were inserted on the inner margin of anterior lobes.

Remarks. Specimens assigned here to M. macintoshi sp. nov. were previously considered to belong to Macellicephala mirabilis by both McIntosh (1905) and Pettibone (1976). New species clearly differs from the holotype of M. mirabilis by having much shorter, tapering to somewhat angular prostomial lobes (Fig. 2B), deeppurple coloration of dorsum, possession of massive tri-lobed facial tubercule and extremely short ventral cirri. See also Remarks under M. mirabilis and Table 2.

In addition, there appears to be confusion about the locality of specimens assigned here to M. macintoshi sp. nov. Whereas the locality stated by Pettibone (1976) for specimens accessed as BMNH: 1924: 7: 21: 12 was South Africa (off Cape Point Lighthouse, 860 m depth), the label inside the vial containing these specimens states South Africa (Cape of Good Hope, 300 –500 fathoms = 540–900 m), as included in the Material examined section in this publication.

Etymology. This species is dedicated to W. C. McIntosh, who described many polychaete species, including the first species of Macellicephala, M. mirabilis (McIntosh, 1885) and who also collected the specimens upon which the description of M. macintoshi sp. nov. is based.