Scalibregma cinthyae Mendes & Rizzo & Paiva 2023, sp. nov.

Scalibregma cinthyae sp. nov.

urn:lsid:zoobank.org:act: 8F8E98A1-EF3B-4A37-AD22-54FA72E96F9A

Figures 1–2, Figure 5 (D–F)

Type material. UERJ8741 (Holotype): SANSED6C2 R2, Lat: -25.0337 Long: -46.8874437185, 51m, 51 m, 18 Nov 2019; UERJ 8744 (Paratype): SANSED4G6 R3, Lat: -23.8161 Long: -42.6755 W, 400 m, 02 Aug 2019, 1 specimen; MNRJP007672 (Paratype): SANSED9G3 R1, Lat: -23.2004 Long: -42.9891, 75 m, 01 Jun 2021, 1 specimen; MNRJP007673 (Paratype): AMBES6 D4 R1, Lat: -19.765386 Long: -39.507150, 150 m, 15 Jan 2012, 1 specimen

Additional material Santos Project: UERJ8742: SANSED2E6 R1, Lat: -24.7424 Long: -44.5050, 400 m, 06 Jul 2019, 1 specimen mounted to SEM; UERJ9215: SANSED9G5 R1, Lat: -23.7040 Long: -42.7342, 150 m, 31 May 2021, 1 specimen. Ambes Project: UERJ 8745: AMBES11 B6 R1, Lat: -20.600447 Long: -39.860875, 1003 m, 17 Jun 2013, 1 specimen.

Diagnosis. Quadrangular prostomium, T-shaped, with two short lateral horns and a small postero-dorsal elevation, near peristomium. Mouth formed by one pair of upper lips and one pair of lower lips. Branchiae present from chaetiger 2–5. Dorsally, anterior region quadriannulate, becoming pentannulated posteriorly. Ventrally, chaetiger 1–2 triannulate, then quadriannulate to pentannulate on posterior chaetigers. Short spinous chaetae present on chaetiger 1 anterior to capillaries, being replaced by 5–6 lyrate chaetae with equal tynes on chaetiger 2.

Description. Holotype 12 mm long for 1–3 mm wide for 34 chaetigers, incomplete, pygidium absent, ovigerous female. Paratypes, 5–12 mm long for 0.2–1 mm wide for 28–45 chaetigers. Large size species, adults measuring 8–12 mm long, and 1–3 mm wide across 27–34 chaetigers. Body arenicoliform, expanded on chaetiger 4–5 up to mid-body segments. Color in alcohol pale tan to yellowish. Body surface covered by annulated secondarily rings, each one formed by numerous rectangular pads anteriorly and quadrangular to rounded pads posteriorly, giving a complex areolate appearance. These pads may have small individual glands inside, blackish, consisting of thin entangled tubules.

Quadrangular prostomium, T-shaped, with two short lateral horns and a small postero-dorsal elevation, near peristomium (Fig. 2A). Eyes absent. Nuchal organs not observed. Peristomium achaetous, dorsally uniannulated, becoming biannulated ventrally (Fig. 1A). Peristomium sometimes with small rectangular pads dorsally, laterally, and ventrally. Mouth formed by one pair of upper lips and one pair of lower lips (Fig. 1A). Upper pair of superior lips present as two parallel rows of paired lobes; with 9–10 paired lobes on superior-most row and 7–8 paired lobes on inferior-most row. Lower pair of inferior lips present as two parallel rows of paired lobes; with 7–10 paired lobes on superior-most row and 10–12 on inferior-most row (Fig. 1A). Ventral groove succeeds inferior-most row of lower lips with a large single pad paired to chaetiger 1 secondarily annuli. Proboscis not observed.

Dorsally, anterior region quadriannulate, becoming pentannulate posteriorly. Ventrally, chaetigers 1–2 triannulate, then quadriannulate to pentannulate on posterior chaetigers (Fig. 2A). Ventral groove from chaetiger 1, with each body segment having a single pad merging with next one, forming a mid-ridge line to posterior end. The first pad larger and undivided (Fig. 1A); following pads may be subdivided two or three times, forming bi or triannulated quadrangular blocks (Fig. 1A).

Branched branchiae present from chaetigers 2–5, posterior to capillaries on notopodia (Figs 1B; 2A). First pair of branchiae small, gradually becoming larger (Fig. 2A). First chaetiger smaller, conspicuous, formed by a main rhomboid pad sustaining a smaller rounded pad from which arise a parapodium with two rows of smooth capillaries, accompanied by 5–6 short, curved and distally pointed spinous chaetae anterior to capillaries (Figs 1C; 2B). Spinous chaetae present on chaetiger 1, being replaced by 5–6 lyrate chaetae with equal tynes on chaetiger 2 (Figs 1D; 2C). Following chaetigers with same rhomboidal pattern, but with longer parapodial lobes; with a knob-like interramal papilla emerging between noto- and neuropodia. Posterior region with a single row of capillaries and 4–5 lyrate chaetae. Ventral and dorsal cirri present from chaetigers 14–17. Parapodial cirri with a gradation in size and shape, with first pair small and rounded, then becoming larger and apically thinner (Fig. 1E–G). Neuropodia of chaetigers 4–6 with a single inferior glandular patch (Fig. 5D, E). Dorsally, chaetigers 4–6 also with a single patch of glands in each annulus of pad (Fig. 5D, E). Blackish glands varying from single entangled cellular stripes to robust tubular structures, covering inner portion of each parapodial cirrus partially to entirely, from its axis to basis, without dorsal or ventral differentiation (Fig. 5F).

Pygidium absent on holotype and most of additional material, but present in some paratypes. When present, it was observed as with a short crenulated margin formed by several paired lobes, bearing three long anal cirri, with two ventro-lateral and one mid-ventral.