Potamethus filatovae Tovar-Hernandez & Jirkov 2024, new combination
Creators: name: Tovar-Hernandez, Maria Ana
name: Jirkov, Igor A.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Sabellida
Sabellidae
Potamethus
Potamethus filatovae

description: Potamethus filatovae (Levenstein, 1961), new combination   
Figures 1–5  
 Jasmineira filatovae Levenstein, 1961, 173, fig. 10.— Hartman, 1965a: 77 (catalogue).— Levenstein, 1966: 75–76.— Levenstein, 1969: 60 (table).— Levenstein, 1973: 132 (table).— Capa & Murray, 2015: 124 (table).— Alalykina, 2020: 200 (table).— Capa et al. 2021: supplementary file (catalogue).   
 Potamethus filatovae — Belyaev, 1989: 181 (table).   
 Type material   
[Shirshov Institute of Oceanology] Bering Sea, R / V Vitjaz, St. 618, 25/9/1950, 3940 m, 57°30’N, 168°30 ‘E (lectotype INV0003597 and 7 paralectotypes INV0001520, 3 of them with intact branchiae) and R / V Vityaz, St. 539, 25/8/1950, 3812 m, 58°39’N, 177°43‘E (8 paralectotypes INV0001521). Bottom temperature 1.56°C and 1.62°C, respectively; bottom salinity 34.60‰ and 34.71‰, respectively; sediment composed of fine silt and claydiatom silt, respectively.  
 Redescription (based on lectotype, with variation of paralectotypes in brackets).   
Body slightly flattened dorso-ventrally. Body length excluding crown 66 (15–85) mm, 3 mm wide. Radiolar crown 24 (15–65) mm long. Crown composed of semi-circular radiolar lobes fused dorsally. Twelve (8–25) pairs of radioles not fused by an inter-radiolar membrane, not arranged into a spiral, without eyes or flanges. Radiolar tips entire, filiform (Fig. 1G). Marginal base of crown with parallel lamellae bordering ventrally (Figs 1B, 2D, E). Anterior and posterior peristomial rings distinctly elongated (Figs 1C, 2A, B). Posterior peristomial ring, commonly known as collar, not covering radiolar bases (Figs 1C, 2D). Mid-ventral margin of collar incised, forming two rounded lappets (Figs 1B, 2E) as long as chaetiger 1. Ventral sacs rounded, exposed outside radiolar crown (Figs 1B, 2E). Lateral collar margin oblique (Figs 1C, 2A), elongate toward ventral side, exposing anterior peristomial ring (Figs 1C, 2D). Dorsal collar margins V-shaped, fused to faecal groove, forming dorsal pockets (Figs 1A, 2A–C). Anterior peristomial ring fully exposed above dorsal collar margins (Figs 1A, 2A–C). Mid-dorsal margin of anterior peristomial ring triangular (Fig. 2B), visible once crown removed. Oval brownish peristomial moldures exposed beyond dorsal collar margins (Figs 1A, 2A–C). Dorsal lips with mid-rib (radiolar appendages), dorsal pinnular appendages absent. Ventral lips ear-shaped. Ventral shield of collar well developed, almost trapezoidal (Figs 1B, 2E). Two diagonal glandular shields at the base of ventral lappets, separated from each other by mid-ventral incision of collar (Figs 1B, 2E).  
Collar chaetae (chaetiger 1) composed of two groups of narrowly hooded chaetae (Figs 3A, B, 4A, B); superior group more longer than two times the length of the inferior group (Fig. 3A). Thorax with 8 chaetigers (Fig. 1D). Ventral thoracic shields well developed, rectangular (Fig. 1D). Glandular ridge on chaetiger 2 visible only dorsally, broad, brownish in lectotype (in some paralectotypes hardly visible).  
Thoracic notochaetae of chaetigers 2–8 with superior group of elongate narrowly hooded chaetae (Figs 3C, D, 4D) and with inferior group of paleate chaetae arranged in 3 rows (Figs 3C, E–H, 4C–E). Bayonet chaetae absent. Thoracic uncini avicular, with handles 7–8 times longer than crest length (Fig. 3J); crest without hood, with 5–6 rows of teeth of nearly equal size above main fang, covering half of main fang (Fig. 3K), and with a small hump on the angle between external margin of neck and handle (a slight swelling opposite to breast). Companion chaetae teardrop shaped, with a narrow dentate head and very long tip (+3 times longer than uncinal main fang), some tips distally enrolled (Fig. 3L–M).  
Abdomen with 51 (26–58) chaetigers. Ventral abdominal shields well developed, oval, with marked brown margins, separated from each other by faecal groove (Fig. 1E). Abdominal neurochaetae with two rows of narrowly hooded chaetae, those of inferior row three times shorter than those in superior row (Fig. 5A–C, E–G); surface covered with fine bristles visible only under SEM (Fig. 5D). Abdominal uncini avicular with a small hump on the angle between external margin of neck and handle (a slight swelling opposite to breast) (Fig. 5J–K); breast as a narrow swelling, handles 2.5 times longer than crest length (Fig. 5J–L), main fang surmounted by 4–5 rows of nearly equal-size teeth above main fang, covering half of main fang (Fig. 5J–I).  
Pygidium with terminal anus (Fig. 1F) and two lateral rounded papillae, visible in some paralectotypes and mentioned in the original description, and without anal cirrus. Tubes silty, smooth, fragile (Fig. 2G). One tube of paralectotype with eggs inside (Fig. 2F).
description: Published as part of Tovar-Hernandez, Maria Ana & Jirkov, Igor A., 2024, Jasmineira filatovae Levenstein, 1961, the deepest known sabellid is a Potamethus Chamberlin, 1919: redescription, new combination and generic emendation, pp. 48-70 in Zootaxa 5486 (1) on pages 49-52, DOI: 10.11646/zootaxa.5486.1.2, http://zenodo.org/record/13209689