Tanaidacea (Crustacea: Peracarida) of the North-east Atlantic: the genera Leptognathioides and Portaratrum of the ‘ Atlantic Margin’ Bird, Graham J. Journal of Natural History 2014 2014-04-23 48 29 - 30 1771 1815 3TPZH Bird, 2014 Bird 2014 [494,819,168,192] Malacostraca Leptognathioides Animalia Tanaidacea 9 1779 Arthropoda species biarticulata sp. nov.    Diagnosis Female: with pereonites all shorter than broad. Cheliped propodus without obvious step process on inferior margin; fixed finger with triangular tooth on incisive margin. Pleopod endopod with one distomedial and five distolateral setae, exopod with proximolateral seta and eight distolateral setae. Uropod exopod two-segmented. Preparatory male: pleopod rami broader than in female, endopod with one distomedial and eight distolateral setae; exopod with proximolateral seta and distolateral fringe of nine setae.    Etymology From the Latin, referring to the two-segmented uropod endopod.    Type locality Bathyal IcelandBasin, ca. 1500–1700 m.   Material examined   Holotypenon-ovigerous ♀( 2.9 mm), BIOICE Stn3538, [IINH 27830], Iceland Basin[slope], 62.24° N 14.13° E,  1518 m, 2.57°C.   Allotypepreparatory ♂( 2.5 mm), BIOICE Stn3069, [IINH 27875], Iceland Basin[slope], 62.29° N 14.30° E,  1607 m, 3.24°C.   Paratypes: one prep. ♂(antennule and pleopod dissected on microslide), two nonov. ♀♀, BIOICESt 3069, [IINH 27876]; one non-ov. ♀, one non-ov. ♀/early prep. ♂, BIOICEStn 3531, [IINH 27877]; two non-ov. ♀♀, BIOICEStn 3532, [IINH 27878]; one manca-III, two non-ov. ♀♀(one partially dissected on microslides), three prep. ♂♂(one early?), BIOICEStn 3538, [IINH 27879]; one ov. ♀, BIOICEStn 3543, [IINH 27880].    Description Female: habitus ( Figure 2A) fairly slender, 6.7 times ltb, slightly tapering posteriorly; length 1.9–2.9 mm(ovigerous female 2.9 mm); cuticle well-calcified, fragile. Cephalothorax ( Figure 2B, C) as long as pereonites 1–2 together, 1.35 times ltb. Pereon with lateral margins of pereonites weakly convex or with slight process at pereopod insertion, becoming more posterior from pereonite-1 to pereonite-6; pereonite-1 shortest, weakly trapezoidal, pereonites 2–4 longest, subequal; pereonites 1–6 0.5, 0.8, 0.8, 0.8, 0.8, and 0.6 times as long as broad, respectively. Pleon ( Figure 2D) almost as long as pereonites 5–6 together, 14–16% of body length; epimera with simple seta. Pleotelson ( Figure 2E) shorter than pleonites 4–5 together, half as long as broad, with two simple setae and two PSS on weakly produced, rounded posterior margin. Antennule ( Figure 2F) article-1 three times ltb, 51 % of total length; article-2 twice as long as broad; article-3 half as long as article-2; article-4 just shorter than article-2, with one aesthetasc with complex tip; other setation as figured. Antenna ( Figure 2G) article-1 simple, naked; article-2 slightly larger than article-3, with small superodistal seta; article-3 as long as broad, with superodistal seta; article-4 6.7 times ltb, with ‘fusion-line’, with two long and one short distal setae and at least one PSS; article-5 about five times ltb, with distal seta; article-6 small with six setae.  Figure 2.  Leptognathioides biarticulata n. sp.Holotype non-ovigerous female: (A) habitus; (B–C) cephalothorax-cheliped, lateral and ventral respectively; (D) pleon, lateral (pleopods omitted); (E) pleotelson. Paratype non-ovigerous female (IINH 27879): (F) antennule; (G) antenna. Scale bars: i: 1 mm for (A), 0.5 mm for (D, E); ii: 0.5 mm for (B, C); iii: 0.25 mm for (F, G). Labrum ( Figure 3A) hood-shaped, distally setulate. Mandibles ( Figure 3B, C) with molar of piercing-crushing type, with about four stout and six slender terminal spines; left incisor narrow, tricuspid, lacinia narrow, bluntly acuminate; right incisor weakly tricuspid. Labium not recovered. Maxillule ( Figure 3D) endite slender with nine terminal spines, three small and two serrulate. Maxilla not recovered. Maxilliped ( Figure 3E) bases together cardiform, with proximal pedestal, distally produced over endites, each with small distal seta; endites weakly flared, with setulate distolateral process, a more medial distal lobe, a medial tubercle and two setae; palp article-2 with long lateral seta, inner margin with three unequal setae, one serrulate; article-3 inner margin with four setae (two long, two short); article-4 with one distal and five terminal setae. Epignath ( Figure 3F) slender, with naked acuminate tip. Cheliped ( Figure 3G, H) robust; sclerite naked; basis with posterior lobe relatively small, with superolateral seta; merus with inferior seta; carpus longer than merus, 1.4 times ltb, with superoproximal seta and two unequal inferior setae; propodus 1.5 times longer than carpus, twice as long as broad, palm with inner comb of three setae; fixed finger with two inferior setae, three setae near incisive margin that has a broad distal tooth, terminal spine robust; dactylus with small inner seta, incisive margin with proximal spine. Pereopod-1 ( Figure 4A) coxa annular, with seta; basis four times ltb, with superoproximal seta; ischium with seta; merus with weak oblique articulation with carpus, 1.75 times ltb, with inferodistal seta and bayonet spine; carpus just longer than merus, with one superodistal and one inferodistal bayonet spines, with small distomedial seta; propodus slender, 4.5 times ltb, superior, inferior, and distal margins with spinules, with superodistal seta and inferodistal spine; dactylus with accessory seta, shorter than unguis, together just over three-quarter length of propodus. Pereopod-2 ( Figure 4B) similar to pereopod-1 but carpus with two inferior bayonet spines. Pereopod-3 ( Figure 4C) similar to pereopod-2. Pereopod-4 ( Figure 4D) basis, with inferior PSS; ischium with two unequal setae; merus almost twice as long as broad, with two inferodistal bayonet spines; carpus subrectangular, as long as merus, 2.4 times ltb, with superodistal seta and three distal bayonet spines; propodus slender, 1.3 times longer than carpus, superior and inferior margins setulate, superior with one PSS; with two unequal inferodistal bayonet spines and one bayonet spine just shorter than dactylus; dactylus slender, weakly spinulate, unguis shorter, slender, together as long as propodus. Pereopod-5 ( Figure 4E) similar to pereopod-4 but basis inferior margin with two PSS. Pereopod-6 ( Figure 4F) similar to pereopod-5 but basis with one PSS and propodus with three superodistal spines. Pleopod ( Figure 5A) peduncle twice as long as broad; endopod 3.3 times ltb, with distomedial seta (weaker than remainder) and five distolateral setae; exopod longer and broader than endopod, four times ltb, two-articled, small proximal article with seta, main article with eight distolateral setae; all setae sparsely plumose.  Figure 3.  Leptognathioides biarticulata n. sp.Paratype non-ovigerous female (IINH 27879): (A) labrum, lateral; (B, C) left and right mandibles respectively; (D) maxillule endite; (E) maxilliped (one palp omitted); (F) epignath; (G) cheliped; (H) cheliped palm and dactylus medial setation. Scale bars: i: 0.25 mm for (A–F); ii: 0. 25 mm for (G, H).  Figure 4.  Leptognathioides biarticulata n. sp.Paratype non-ovigerous female (IINH 27879): (A–F) Pereopods 1–6 respectively. Scale bar: 0.25 mm.  Figure 5.  Leptognathioides biarticulata n. sp.Paratype non-ovigerous female (IINH 27879): (A) pleopod (all setae weakly plumose); (B) uropod. Allotype preparatory male: (C) Habitus. Paratype preparatory male (IINH 27876): (D) antennule; (E) pleopod. Scale bars: i: 0.25 mm for (A, B, D, E); ii: 1 mm for (C). Uropod ( Figure 5B) as long as pleotelson and pleonite-5 together; exopod twosegmented. Manca-III: length 1.7 mm. Preparatory male: habitus ( Figure 5C) generally similar to female; length 2.4–2.6 mm. Pleon proportionally slightly larger than female, 18% of body length. Antennule ( Figure 5D) articles 1–3 broader than female, article-1 2.4 times ltb. Pleopod ( Figure 5E) rami broader than female, endopod with one superodistal and eight distal setae; exopod with proximal seta and distal fringe of nine setae.    Distribution in main study area Represented by five records from the IcelandBasin (slope), at depths 1518– 1710 m, and bottom temperature 5°C ( Figure 12). Only one station (BIOICE Stn 3531) had associated sediment data, as ‘sandy silt’. See also remarks on ‘  Leptognathioidessp.indet.’ below. It was sympatric (same sample, BIOICE Stn 3069) with  Portaratrum holdichi n. sp.(see below) and its bathymetric range does not overlap with  L. polita.   Distribution elsewhere No records.    Remarks This species is very similar to  L. politabut differs having a clearly two-segmented uropod exopod and fewer pleopod setae.  L. biarticulata n. sp.may also have slightly longer superodistal carpal spines on pereopods 1–3. It is also smaller at equivalent life-stages but this is not definitive as it is based on a relatively small sample. A very similar abyssal species,  Leptognathioidessp.KK#1, is present in the Kurile- Kamchatka Trench at 5473–5484 m( Bird 2007, p. 146, fig. 149) that remains undescribed. The proportions of its cheliped basis and the setation of the pereopod- 1 carpus suggest that it is distinct from  L. biarticulata. A small distal segment on the uropod exopod is very unusual among paratanoideans, as two-segmented examples are mostly subequal or have a shorter proximal segment as in  Heterotanoides(e.g. Bird 2012, fig. 1H); this might be seen as atavistic. BIOICE Iceland 1518 62.24 Stn 612 14.13 Basin 9 1779 1 1 holotype BIOICE Iceland 1607 62.29 Stn 612 14.3 Basin 9 1779 1 1 allotype BIOICE 9 1779 9 6 3 paratype