A new species of Melinnopsis (Annelida, Melinnidae) from the Porcupine Abyssal Plain, northeast Atlantic Author Gunton, Laetitia M. 0000-0003-4758-4974 School of Ocean and Earth Science, University of Southampton, Southampton, SO 14 3 ZH, UK Author Serpell-Stevens, Amanda https://orcid.org/0009-0009-1153-3033 National Oceanography Centre Southampton, Southampton SO 14 3 ZH, UK Author Riaz, Kashaf School of the Environment and Life Sciences, University of Portsmouth, King Henry Building, Portsmouth PO 1 2 DY, UK Author Horton, Tammy 0000-0003-4250-1068 National Oceanography Centre Southampton, Southampton SO 14 3 ZH, UK text ZooKeys 2025 2025-12-23 1265 1 23 journal article 313574 10.3897/zookeys.1265.171206 b2e6df92-10b6-4724-99da-3feeafda87ea 8E086E9A-4BB5-4D7A-A2D1-2EBD336E9FB7

Table 4. Comparison of all known species of Melinnopsis McIntosh, 1885. Updated table from Gunton et al. (2020: table 3), adapted from Hilbig (2005: table 3). * type species. TU, thoracic uncini. TC, thoracic chaetigers. Dashes (—) indicate not mentioned in original description.

Species	No. of TU	Dorsal membrane segment V	Buccal tentacles	Branchiae	No. of teeth above rostral tooth in TU	Body size (length: width)	Tube	Type locality
M. abyssalis (Hartman, 1969)	12	Absent	2 types: 1 large, many small	4 pairs: 1 anterior middle pair largest, 3 pairs in a crescent shape	3	52 mm: 3 mm	135–150 mm long, 3–4 mm wide, tapering slightly, smooth, dark silt	San Clemente basin, NE Pacific, 1920 m
M. angolensis Hilbig, 2005	13	Present: serrated (up to 21 teeth)	2 types: 4–6 large, 6 small	4 pairs: 1 anterior middle pair largest	2	21–50 mm: 3–4 mm	Up to 3 × length of worm, muddy with fine inner mucus lining	Angola Basin, SE Atlantic, 5385–5439 m
M. annekovae (Uschakov, 1952)	12	Absent: well-developed glandular band on segment four	2 types: 1 large> 7 mm, 3–4 small	4 pairs: 1 median pair largest	3 (5 teeth in one row)	—: 3 mm	Sturdy silted tube	Arctic Ocean, 51–1900 m
M. atlantica * McIntosh, 1885	14?	Present smooth (between segment 4 and 5)	None visible	4 pairs: unclear (no scars visible on re-examination of type material)	3 (top tooth indistinct) assuming pl. XXVIIA fig. 18 is thoracic	35 mm: 3 mm	Stiff cylinder, fine grey mud, Foraminifera attached	Off Chesapeake Bay, NW Atlantic, 3109 m
M. arctica (Annekova, 1931)	12	Present / indistinct, assuming ' dorsal fold' is the same as ' dorsal membrane'	2 types: 1 large, 2 small	4 pairs: anterior (inner) larger than others	2	25 mm: 3 mm	Solid tube like Melinna cristata covered in sand in the front part	Arctic Ocean, 165–480 m
M. armipotens (Moore, 1923)	13?	Absent / indistinct	2 types: 1 large (12 mm long 8 mm wide), few small (1 mm long)	4 pairs: anterior (largest by one-third)	3	31 mm: 1.3 mm	—	Santa Catalina Islands, NE Pacific, 4070 m
M. augeneri Reuscher et al., 2015	13	Indistinct, no serration	2 types: 4 long thick and annulated, 3 small	4 pairs: arranged in continuous arch	2	14 mm: 0.8 mm	—	Goto-Kasayama Bank, west of Kyushu, 185 m
M. chadwicki Gunton et al., 2020	12	Absent / indistinct	2 types: 1 long, 6 small	4 pairs: 1 pair slightly anterior	2	22 mm: 1 mm	Fine-grained sediment sometimes with green veins and Foraminifera	Eastern Australia, 1006–1257 m
M. collaris (Hartman, 1967)	12	Absent	2 types: 1 large, many small	4 pairs: crescent shape, 1 pair anterior	—	46–51 mm: 4.6 mm	Long, tough, covered with silt, internal membrane	Mid-Pacific Basin, 4041–4813 m
M. dubita (Hoagland, 1920)	12?	Indistinct ridge	2 types: 6 tentacles up to 15 mm, many smaller 3–7 mm	4 pairs: unclear	3 assuming pl. 51 fig. 5 thoracic	15 mm: 7 mm	Fine brown mud	Mindanao, Philippines, 920 m
M. gardelli Gunton et al., 2020	12	Indistinct	2 types: 1 long 34 mm and shorter tentacles 2 mm	4 pairs: 1 pair anterior	3	40 mm: 4 mm	Fine-grained sediment sometimes with green veins and Foraminifera	Eastern Australia, 2520–2821 m
M. mcintoshi Reuscher, Fiege & Imajima, 2015	13	Present: smooth	2 types: 3 long thick, annulated, 4 thinner	4 pairs: 2 rows of 2	2	44 mm: 2 mm	—	Japan, Pacific Ocean, 164–5600 m
M. monocera (Augener, 1906)	12	Indistinct	2 types: 1 long (length 26 anterior segments), 6 short	4 pairs: unclear	2	28–42 mm: 2 mm	—	Caribbean, 212–310 m
M. moorei (Hartman, 1960) using Moore 1923	13? (17 TC)	Present: slightly serrated	—	4 pairs: cluster on each side	2	80 mm: —	Heavy mud walls	Off Santa Catalina and San Miguel Islands, NE Pacific, 495–3990 m
Melinnopsis nathanieli sp. nov.	12–14	Absent / indistinct	2 types: 1 long up to 15 mm, 4 small 1 mm	4 pairs: 1 pair anterior	3	48 mm: 3 mm	Fine-grained sediment	Porcupine Abyssal Plain, northeast Atlantic, 4843–4850 m
M. rostrata (Wesenberg-Lund, 1950)	12	Present: 15–17 teeth	2 types: 5 long curled, 3 shorter	4 pairs: 1 pair anterior	—	72 mm: —	—	West of Greenland, Arctic, 3229 m
M. shinkaiae Jimi, Hookabe, Woo & Fujiwara 2025	12	Absent	2 types: 1 long, 5 small	4 pairs: 1 pair anterior	3	22 mm: 1 mm	mud, with sponge spicules	Daiichi-Kashima Seamount, Northwest Pacific, 3623 m
M. somovi (Uschakov, 1957)	12	Absent	2 types: 1 large, some small	3 pairs: Internal largest	2	15 mm: 1 mm	Silt with Foraminifera shells and small stones	Arctic, 1239–1694 m
M. tentaculata (Treadwell, 1906)	—	—	2 types: 1 large length of anterior region of body. 2 or 3 smaller	4 pairs: 2 rows, outer pair largest	3	9 mm: 1.5 mm	Thick mud tube with sponge spicules	Hawaii, 508–1358 m
M. tetradentata (Imajima, 2001)	13	Present: serrated 14 dentations	2 types: 1 long trihedral. Multiple shorter ones	4 pairs: 2 rows of 2	2	70 mm: 4 mm	Thick, dark, fine-grained mud particles, thin inner membrane	Tosa Bay, Japan, 400–800 m