Hirsutocrinus duplex, Mironov & Fujita, 2021

Mironov, Alexandr N. & Fujita, Toshihiko, 2021, Hirsutocrinus duplex, a New Genus and Species of Sea Lilies (Crinoidea, Comatulida, Bathycrinidae) from the Western North Pacific, Species Diversity 26 (1), pp. 101-110 : 102-108

publication ID	https://doi.org/ 10.12782/specdiv.26.101
publication LSID	lsid:zoobank.org:pub:D34C3DD4-97A4-41CE-8208-D6A403C146DF
persistent identifier	https://treatment.plazi.org/id/9E2987C3-FFF1-F839-FA88-CBF640C0F784
treatment provided by	Felipe
scientific name	Hirsutocrinus duplex
status	sp. nov.

Treatment

Hirsutocrinus duplex n. sp.

( Figs 1–5 View Fig View Fig View Fig View Fig View Fig )

Bathycrinus pacificus non A. H. Clark, 1907: Kogo and Fujita 2005: 234 (in part).

Etymology. The specific epithet is derived from the Latin word duplex in reference to the presence of the knobby processes at two levels: on IBr2 and Brs 1–2.

Diagnosis. Radials and primibrachials rather short; ratios RRH/RRD and IBr2H/Br2W<1.0. Number of knobby processes on primibrachials 4. External surface of IBrs and Brs covered by dense needle-like spines. Brachial pattern the same in proximal and distal free arm: 1+2 4+5 7+8 10+11 13+14 and so on. P1 on Brs 8–10. Starting with the brachial bearing P1, every third brachial lack pinnule. Strong distinction between the cover and side plates in pinnules. Tube feet with x-shaped plates. Sacculi absent. Mesistele synarthries with moderate ligament depression. Dististele synarthries strongly oval with regular secondary crenularium on fulcral ridge axis. Distal end of stalk with rootlike radix.

Holotype. NSMT E-5200 .

Type locality. North of Kuroshima Island , Okinawa Prefecture, Japan . RV Toyoshio-maru , St . 11, 24 May 2003, 26º19.18′N, 127º25.56′E, depth 596– 606 m.

Material examined. Only holotype restricted to RR-ring with incomplete arms, two fragments of arms, and two fragments of stalk.

Description. Radial ring inverted conical, broader than high ( Figs 1A View Fig , 2A View Fig ). RRD= 1.97 mm; RRH/RRD=0.66. RR external surface with numerous fine longitudinal ribs. Tegmen raised up to distal part of Br2. Ambulacral grooves not reaching oral opening, extending out to circumoral elevation of soft tissue. Two oral tentacles located in each interradius at aboral margin of circumoral elevation; two flat rounded plates located aborally of these oral tentacles. Oral tentacles differing from neighbouring ambulacral tube feet in having much larger size and non-transparent soft tissue. Plates at the top of tegmen various in shape and size ( Fig. 3C View Fig ). The rounded plates on the sides of tegmen ( Fig. 3A View Fig ) and low anal sac ( Fig. 3B View Fig ) less diverse in shape; the latter somewhat thicker than the former.

Length of IBr1+2 2.45 mm; ratio IBr1H/RRH approximately 1.0; IBr1H/Br2L 1.12; IBr1H/Br1 W 1.04; IBr2H/ Br2 W 0.82. First and second primibrachials slightly broader distally than proximally ( Figs 1A View Fig , 2A View Fig ); their sides flattened into wide lateral flanges ( Fig. 1A View Fig ). Broad rounded keel with fine ribs. All IBrs 1 without knobby processes ( Fig. 2C View Fig ). IBrs 2-circle with 4 knobby processes: one of IBrs 2 with two knobby processes, two IBrs 2 with one knobby process confined to the upper part of IBr2, and two IBrs 2 without knobby processes. Articular surface of knobby processes covered by small sharp spines not arranged in parallel pattern ( Fig. 2D, E View Fig ).

Lateral compression of corona indistinct. All free arms incomplete: 5 with 9 Brs, others with 6, 11, 13, 30, 43 respectively, the best-preserved (43 Brs) approximately 25.5 mm long, with 13 Ps on a side. Arm fragment 13.7 mm long with 21 Brs. Lateral flanges wide in proximal Brs ( Figs 2F, G, I, J View Fig , 4A View Fig ), becoming progressively narrower distally; distal to Br28 continues as low longitudinal rib ( Fig. 1E View Fig ). Brs 1–12 with broad rounded keel; profile of this part smooth viewed from side ( Fig. 1F View Fig ). Brs 13–24 with narrower and sharper median keel including a small tooth in every hyposynostosial Br. Distal to Br24 arm profile serrated ( Fig. 1E View Fig ). External surface of Brs covered by dense needle-like spines ( Figs 2G View Fig , 4B, C View Fig ). Brachial side surface with fine ribs near the pinnule socket ( Fig. 1F View Fig ). Each Br2 and some Brs 1 bearing a single knobby process. Process developed along the entire length of the Br2 ( Fig. 2H, I View Fig ) and restricted to the distal part of Br1 ( Fig. 2J View Fig ). The knobby processes of adjacent free arms (attached to the same IBr2) in contact with each other by spiny articular surface.

P1 on outer side of Br 8 in three arms, on inner side of Br 9 in four arms, position unknown in three arms. Among three arms without P1, two with 9 Brs, suggesting P1 located on Br10 or more distally. Proximal and distal free arm pattern alternating brachial pairs and free brachials (1+2 4+5 7+8 and so on), with the single exception in the best-preserved arm (+17 20+). Starting with the brachial bearing P1, every third brachial lack pinnule. As viewed from side, every third eter of columnals decreasing from 0.76 in proximalt columnal to 0.65 mm in columnal 19, then increasing slowly up to 1.60 mm in columnal 62. Maximum H/D 2.8 at columnal 31. Synarthries articulating mesistele columnals of moderately ovoid facets with only discrete ligament depressions; fulcral ridge axis always corresponding to the greatest facet diameter and forming two main segments connected by perilumen stereom ( Fig. 4D View Fig ). Synarthries articulating dististele columnals strongly ovoid, with deep ligament depressions; maximum D/d ratio in distalmost columnals 1.75; fulcral ridge separated in two segments by axial canal, with regular relief on secondary crenularium ( Fig. 4E, F View Fig ). Only proximal part of root-like radix preserved ( Fig. 2B View Fig ).

Br with P ( Fig. 1E View Fig ). Muscular and non-muscular synarthrial facets of free arms with classical features ( Figs 2F, G View Fig , 4A View Fig ). Among Ps only four Ps 1 complete. Ps 1 consisting of 7–8 Pns, 2.33–2.69 mm long ( Fig. 1F View Fig ). Length of Ps increases from P1 at least to P4, longer than 3.6 mm and with more than 10 Pns. Articulation between all Pns beyond the first pair rigid. Relative length of Pns variable ( Table 2). Pns 3–4 longest in Ps 1; Pns 3–5 longest in Ps 5–7. Pns from genital inflation strongly asymmetric in cross section, with its outer side much longer than inner side.

Shape of both cover and side plates varying from proximal to distal arm. The variability is highest at Brs 2–4 ( Fig. 3D View Fig ) and cover plates not easily distinguished from side plates, but the former with less dense stereom, sometimes bushy in shape, the latter usually ovoid. In distal arm and pinnules, both cover and side plates with more or less constant shape and clearly differ from each other ( Fig. 3F, G View Fig ). Side plates of typical shape first appearing on the Brs 5–8 ( Fig. 3E View Fig ). Typical cover plates first appearing distally from Brs 8–10. Ambulacral tube feet with a few x-shaped plates located only in the basal part. The most basal tube feet plate irregular in shape and much larger than the other plates ( Fig. 5 View Fig ).

Stalk broken in two fragments, but almost completely preserved; only proximalmost columnals missing; the first four preserved columnals chipped ( Figs 1B–D View Fig , 2B View Fig ). Stalk 94.7 mm long (excluding radix), with 62 columnals. Diam-