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Deepest known novel species of the genus Ophiuroglypha Hertz, 1927 (Echinodermata: Ophiuroidea) from the central rift zone, Philippine Sea
Get PDFNethupul, Hasitha, Stöhr, Sabine, Zhang, Haibin (2023): Deepest known novel species of the genus Ophiuroglypha Hertz, 1927 (Echinodermata: Ophiuroidea) from the central rift zone, Philippine Sea. European Journal of Taxonomy 891: 167-185, DOI: https://doi.org/10.5852/ejt.2023.891.2281, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2281/983
Fig. 10. Gorgonocephalus chilensis novaezelandiae Mortensen, 1924 in New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach
No full textFig. 10. Gorgonocephalus chilensis novaezelandiae Mortensen, 1924, SEM (IDSSE EEB-SW0005). A. Plan view of the baseplate. B. Distal view of the baseplate. C. Arm spine on proximal lateral plate. D. Pedicellaria on the pedicellarial band. E–I. Vertebrae. E. Proximal view. F. Distal view. G. Ventral view. H. Dorsal view. I. Lateral view. Abbreviations: ap = articular pad of the base; au = auricle; D = dorsal; Dist = distal; fo = foramen of the base; fs = fossa between adjacent tubercles; hd = head of the apophysis; lp = lateral pores of the blade; pd = pedicel of the apophysis; Prox = proximal; pt = primary tooth of the blade; sh = sheath of the baseplate; st = secondary inner tooth; su = sulcus of tubercle head; V = ventral. Scale bars: A–C = 100 µm; D = 20 µm; E, G–I = 300 µm; F = 200 µm.Published as part of Nethupul, Hasitha, Stöhr, Sabine & Zhang, Haibin, 2022, New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach, pp. 1-95 in European Journal of Taxonomy 810 (1) on page 23, DOI: 10.5852/ejt.2022.810.1723, http://zenodo.org/record/641952
Asteronyx loveni Muller & Troschel 1842
No full textAsteronyx loveni Müller & Troschel, 1842 Figs 2–3 Asteronyx loveni Müller & Troschel, 1842: 119–120, pl. 10 figs 3–5. Ophiuropsis lymani Studer, 1884: 55–46, pl. 5 fig. 12a–d. Asteronyx dispar Lütken & Mortensen, 1889: 185, pls 21–22. Asteronyx locardi Koehler, 1895: 470–471, fig. 10. Asteronyx cooperi Bell, 1909: 22. Ophiuraster patersoni Litvinova, 1998: 441–444, fig. 3. Asteronyx loveni – Döderlein 1927: 59, 97, pl. 7 figs 7–8. — Baker 1980: 12, 16–18, figs 2–3. — Liao & Clark 1995: 165–166, fig. 71. — McKnight 2000: 8, 13–15, pl. 1. — Olbers et al. 2019: 49–50, fig. 23. Ophiuraster patersoni – Stöhr 2005: 545–546, fig. 1. Material examined CHINA • 1 spec.; South China Sea, SE of Hainan Island, seamount; 18°31.76′ N, 112°40.56′ E; depth 1167 m; 27 Jun. 2019; collection event: stn SC002; MSV Shenhaiyongshi leg.; preserved in -80°C; GenBank: MZ 198756, MZ 203264; IDSSE EEB-SW0002. Remarks Disc diameter 11 mm and collected attached to a gorgonian species. Our specimen is similar to the holotype description by Müller & Troschel (1842) and later published descriptions (Baker 1980; McKnight 2000; Olbers et al. 2019) (Fig. 2). Vertebrae with a streptospondylous articulation and the lateral arm plate bears four to five spine articulations, which lack a separate nerve opening (Fig. 3). Species of Asteronyx are usually found on mud and sand, associated with gorgonians and pennatulids. In 1959 and from 1976 to 1981, 52 specimens of A. loveni were collected from the East and South China seas, at depths of 510–1100 m. Asteronyx loveni was first reported from the South China Sea by Chang et al. (1962). Distribution 62–4721 m depth. Global, except Arctic and Antarctic (Olbers et al. 2019; OBIS 2021).Published as part of Nethupul, Hasitha, Stöhr, Sabine & Zhang, Haibin, 2022, New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach, pp. 1-95 in European Journal of Taxonomy 810 (1) on pages 11-12, DOI: 10.5852/ejt.2022.810.1723, http://zenodo.org/record/641952
Ophiomusa undetermined
No full textOphiomusa sp. Fig. 13H–L Material examined CHINA • 1 spec.; South China Sea, near Xisha Islands; 16°39.75′ N, 112°7.43′ E; depth 663 m; 15 Mar. 2020; collection event: stn SC006; MSV Shenhaiyongshi leg.; preserved in -80°C; GenBank: MZ 198764; IDSSE EEB-SW0010. Remarks We collected a damaged specimen that could only be identified to genus level as Ophiomusa. It differs from O. lymani by the coverage of irregular scales on the disc center, the radial shields being smaller and more triangular, large ventral disc scales connected to the oral shield entirely covering the interradial space between the genital plates and having an ventral arm plate present on up to seven arm segments from the arm base (Fig. 13H–L). Ophiomusa sp. forms a sister clade to O. lymani on our molecular tree (see below). In the phylogeny by Christodoulou et al. (2019), this sister clade is composed of O. faceta (Koehler, 1922a) and O. facunda (Koehler, 1922a), which suggests that our specimen may also belong to one of these species. Ophiomusa faceta is similar to Ophiomusa sp. by having irregular disc scales on the disc center and radial shields separated by a single layer of disc scales, but differs by lacking a ventral arm plate beyond the second arm segment, smooth dorsal disc surface and 6–7 arm spines on the lateral arm plate. Ophiomusa facunda is similar to Ophiomusa sp. by having a rough dorsal disc surface and radial shields separated by a single layer of disc scales, but differs in having large dorsal disc scales, the entire ventral surface occupied by a large interradial scale, in lacking a ventral arm plate beyond the third arm segment and having 6–7 arm spines on the lateral arm plate. The differences between those species and our specimen prevent us from associating it with either of them. Superorder Ophintegrida O’Hara, Hugall, Thuy, Stöhr & Martynov, 2017 Order Ophiacanthida O’Hara, Hugall, Thuy, Stöhr & Martynov, 2017 Suborder Ophiacanthina O’Hara, Hugall, Thuy, Stöhr & Martynov, 2017 Family Ophiotomidae Paterson, 1985 Genus Ophiotreta Verrill, 1899Published as part of Nethupul, Hasitha, Stöhr, Sabine & Zhang, Haibin, 2022, New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach, pp. 1-95 in European Journal of Taxonomy 810 (1) on pages 28-31, DOI: 10.5852/ejt.2022.810.1723, http://zenodo.org/record/641952
Ophiactis profundi Lutken & Mortensen 1889
No full textOphiactis profundi Lütken & Mortensen, 1889 Figs 38–39 Ophiactis profundi Lütken & Mortensen, 1889: 140–142, pl. 6 figs 4–6. Ophiactis pteropoma H.L. Clark, 1911: 134, fig. 50. Ophiactis pteropoma – H.L. Clark 1915: 264. — Matsumoto 1917: 154. Ophiactis profundi – Koehler 1922a: 192, pl. 63 fig. 8. — Guille 1981: 439. — Liao 2004: 235–236, fig. 139. Material examined CHINA • 1 spec.; South China Sea, SE of Zhongsha Islands, seamount; 13°58.65′ N, 114°52.09′ E; depth 1550 m; 25 Sep. 2020; collection event: stn SC013; MSV Shenhaiyongshi leg.; preserved in 95% ethanol; GenBank: MZ 198771; IDSSE EEB-SW0017 • 1 spec.; same collection data as for preceding; GenBank: MZ 198772; IDSSE EEB-SW0018 • 5 specs; same collection data as for preceding; IDSSE EEB-SW0064 to EEB-SW0068. Remarks Ophiactis profundi is a hexamerous, fissiparous species. The disc diameter ranged from 4 mm to 6 mm and all the specimens were found at one station on a deep-sea seamount in the South China Sea. Morphological descriptions of the holotype of Ophiactis profundi (Lütken & Mortensen 1889) from the eastern Pacific Ocean and of other specimens from the Philippine Sea (Koehler 1922a) were similar to our specimens (Fig. 38). The dorsal arm plates are well-developed, widely triangular (Fig. 39A). The lateral arm plate has three well-developed arm spine articulations, formed by two subparallel bent lobes, not connected to each other, placed at an angle to the distal edge and equal in size, with two similar openings for muscle and nerve (Fig. 39B–C). The vertebrae have a well-developed zygospondylous articulation, with a narrow, shallow dorsal furrow, not extending beyond the distal articulation, and the ambulacral groove is distalwards widened (Fig. 39D–F). Ophiactis profundi is closely related to Ophiactis flexuosa Lyman, 1879, but it differs in the shape of the oral shield and ventral arm plate, the shape of the oral papillae and the number of arms (O. flexuosa is pentamerous). Ophiactis flexuosa has distinct scales all around the radial shields (Lütken & Mortensen 1889). Ophiactis plana Lyman, 1869 is related to O. profundi, but it differs in the shape of the adoral shields and oral shield, and in the smaller oral papillae. Distribution 231–1644 m. From the South China Sea recorded from the Lubang Islands near the Philippines (this part of the South China Sea is sometimes called the West Philippine Sea), East China Sea, Bohol Sea, Gulf of Tomini, Bismarck Sea, Coral Sea, Australia and New Zealand (OBIS 2021).Published as part of Nethupul, Hasitha, Stöhr, Sabine & Zhang, Haibin, 2022, New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach, pp. 1-95 in European Journal of Taxonomy 810 (1) on page 68, DOI: 10.5852/ejt.2022.810.1723, http://zenodo.org/record/641952
Gorgonocephalus dolichodactylus Doderlein 1911
No full text<i>Gorgonocephalus</i> cf. <i>dolichodactylus</i> Döderlein, 1911 <p>Figs 11–12</p> <p> <i>Gorgonocephalus dolichodactylus</i> Döderlein, 1911: 34–36, pl. 1 figs 4–5, pl. 7 figs 3, 4a–b.</p> <p> <i>Gorgonocephalus dolichodactylus</i> – Döderlein 1927: 27, 52. — Matsumoto 1915: 73, fig. 20. — Baker 1980: 52, figs 18a, 20, 30. — Liao & Clark 1995: 171, fig. 75. — McKnight 2000: 45–46, pl. 20.</p> Material examined <p>CHINA • 1 spec.; South China Sea, Zhongsha Islands, seamount; 13°36.00′ N, 114°34.49′ E; depth 1340 m; 30 Mar. 2020; collection event: stn SC008; MSV Shenhaiyongshi leg.; preserved in -80°C; GenBank: MZ 198760; IDSSE EEB-SW0006.</p> Remarks <p> The disc diameter was 67 mm. Our specimen is similar to the holotype description by Döderlein (1911) and the description in Liao & Clark (1995), but showed some morphological variations, especially on the disc (Fig. 11). Therefore, we hesitate to fully associate our specimen with <i>G</i>. <i>dolichodactylus</i>. The original description and the description in Liao & Clark (1995) mention small granules on both the dorsal and ventral disc, but the present specimen is completely naked except for the radial shields (Fig. 11A–E), which are covered by scattered granules (Fig. 11F).</p> <p> Pedicellarial bands are formed by approximately 12 articulating tubercles at the curved distal end of the baseplate (Fig. 12B), and these articulations have a single foramen (Fig. 12C). The distal end of the baseplate internal side becomes curved with perforations on the ventral side of the baseplate (Fig. 12B–C). The vertebrae have a streptospondylous articulation with smooth lateral furrows and no oral bridge (Fig. 12D–H). The external side of the lateral arm plate has three separate tubercle-shaped articulations with a single opening and one large muscle opening at the edge. <i>Gorgonocephalus dolichodactylus</i> was first recorded from the South China Sea in southeastern Hainan, at a depth of 1100 m, in 1959.</p> Distribution <p>146–1357 m depth. South China Sea, Japan, Korea, Philippines, Australia and New Zealand (Liao 2004; OBIS 2021).</p> <p> Order Ophiurida Müller & Troschel, 1840 sensu O’Hara <i>et al.</i> 2017</p> <p>Suborder Ophiomusina O’Hara, Hugall, Thuy, Stöhr & Martynov, 2017</p> <p>Family Ophiomusaidae O’Hara, Stöhr, Hugall, Thuy & Martynov, 2018</p> <p> Genus <i>Ophiomusa</i> Hertz, 1927</p>Published as part of <i>Nethupul, Hasitha, Stöhr, Sabine & Zhang, Haibin, 2022, New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach, pp. 1-95 in European Journal of Taxonomy 810 (1)</i> on pages 25-28, DOI: 10.5852/ejt.2022.810.1723, <a href="http://zenodo.org/record/6419522">http://zenodo.org/record/6419522</a>
Ophiurothamnus clausa
No full textOphiurothamnus clausa (Lyman, 1878) Figs 23–24 Ophioceramis clausa Lyman, 1878: 124, pl. 6 figs 161–163. Ophiothamnus stultus Koehler, 1904: 141–142, pl. 25 figs 9–10, pl. 26 fig. 1. Ophiurothamnus musorstomae Guille, 1981: 427, fig. 1g –j, pl. 3 figs 20–21. Ophioceramis clausa – Lyman 1882: 26, pl. 11 figs 4–6. Ophiurothamnus stultus – Matsumoto 1917: 130. — Koehler 1922a: 104–105, pl. 22 fig. 1–4. — Liao 2004: 149, fig. 78. Ophiurothamnus clausa – O’Hara & Stöhr 2006: 105, fig. 14 (a–j). — Chen et al. 2020: 651–652, figs 1–2. Material examined CHINA • 1 spec.; South China Sea, SE of Hainan Island, seamount; 17°17.60′ N, 111°34.17′ E; depth 1500 m; 2 Apr. 2018; collection event: stn SC021; MSV Shenhaiyongshi leg.; preserved in 95% ethanol; GenBank: MZ 198777; IDSSE EEB-SW0023 • 2 specs; South China Sea, SE of Hainan Island, seamount; 17°59.21′ N, 111°01.17′ E; depth 1500 m; 1 Apr. 2018; collection event: stn SC020; MSV Shenhaiyongshi leg.; preserved in -80°C; IDSSE EEB-SW0042, IDSSE EEB-SW0043. Remarks The disc diameter (4.5–5.0 mm), the circular disc and the morphology are similar to the description of Ophiurothamnus clausa in O’Hara & Stöhr (2006) and to the description from the South China Sea in Chen et al. (2020), but we identified some variability in the number of scales on the dorsal disc and in the shape of the radial shields (Fig. 23). The arm skeleton characters of O. clausa differ from those of other species in the family Ophiacanthidae. The dorsal arm plate is triangular and well developed (Fig. 24A). The arm spine articulation is well developed and has a large muscle opening and a small nerve opening. A volute-shaped perforated lobe is present in most articulations, but is lacking in the dorsalmost one (Fig. 24B). A perforation is present on the inner side of each lateral arm plate (Fig. 24C). The vertebrae have a long streptospondylous articulation, with broad proximal and distal ends and a narrow middle segment. The proximal end of a vertebra has two clearly separated openings and the distal end of the podial basin becomes short and small. The dorsal side of the vertebrae is distally triangular and proximally flattened, without a keel. The ventral side of the vertebrae has a narrow and straight ambulacral furrow without an oral bridge (Fig. 24D–G). Ophiurothamnus clausa has variable morphological features according to O’Hara & Stöhr (2006), especially regarding the characters of the disc, and the variation in disc covering is very striking, ranging from smooth naked plates to plates with granules, the number and shape of the scales covering the disc, the shape and position of the radial shields and the shape of the arm spines. These character differences cannot be explained by biogeographic distribution or size of the animal (O’Hara & Stöhr 2006) and may instead be evidence of cryptic speciation. Distribution 480–3202 m depth. East China Sea, South China Sea, Indonesia, Australia, New Zealand, Kermadec Islands, Philippines, New Caledonia, Papua New Guinea, Mozambique Channel (O’Hara & Stöhr 2006; OBIS 2021). Genus Ophioplinthaca Verrill, 1899Published as part of Nethupul, Hasitha, Stöhr, Sabine & Zhang, Haibin, 2022, New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach, pp. 1-95 in European Journal of Taxonomy 810 (1) on pages 44-47, DOI: 10.5852/ejt.2022.810.1723, http://zenodo.org/record/641952
Ophioplinthaca plicata
No full textOphioplinthaca plicata (Lyman, 1878) Figs 25–26 Ophiomitra plicata Lyman, 1878: 150, pl. 8 figs 209–212, pl. 9 figs 233–235. Ophioplinthaca vicina Koehler, 1904: 129-130, pl. 25 figs 1–3. Ophiomitra plicata – Lyman 1882: 203–204, pl. 10 figs 7–9. — Li 1987: 143–145, pl. 1 fig. 2. — Liao 2004: 139–140, fig. 70. Ophioplinthaca plicata – O’Hara & Stöhr 2006: 84–85, fig. 8g, m–p. Material examined CHINA • 1 spec.; South China Sea, Zhongsha Islands, seamount; 15°36.20′ N, 113°33.74′ E; depth 1820 m; 27 Sep. 2019; collection event: stn SC014; MSV Shenhaiyongshi leg.; preserved in 95% ethanol; GenBank: MZ 198773, MZ 203269; IDSSE EEB-SW0019. Remarks The present study found only one specimen of O. plicata , with 12.5 mm in disc diameter (Fig. 25). Within Chinese waters, this species has previously been recorded only from the South China Sea. The arm spine articulation is well developed and placed at a slight angle to the distal edge of the lateral arm plate. A volute-shaped perforated lobe is present in most articulations, but is reduced in the dorsalmost one (Fig. 26A–B). The arm spine articulation has a large muscle opening and a small nerve opening (Fig. 26A–B), and it decreases significantly in size ventralwards (Fig. 26A). The vertebrae have a streptospondylous articulation, with a short, broad podial basin at the proximal end and a narrow, small distal end. The dorsal end of the vertebrae is distally triangular and proximally flattened with a longitudinal groove along the midline (Fig. 26C–G). The ventral end of the vertebrae has a broad ambulacral groove without an oral bridge (Fig. 26E). The genus Ophioplinthaca is clearly distinguishable from other genera within the family Ophiacanthidae by the deep interradial incisions into the disc, which are lined distally by enlarged disc scales. Ophioplinthaca plicata is morphologically variable among individuals and is difficult to distinguish from other species of Ophioplinthaca, especially from O. pulchra Koehler, 1904. The morphological features of the specimen of O. plicata from our collection and previous descriptions show complex morphological variation among individuals, and more specimens need to be analyzed from neighboring seas and the Indo-Pacific region to understand their morphological variation with respect to geographic distribution (O’Hara & Stöhr 2006). A molecular analysis using specimens from many localities is required to understand the genetic variation in this species and its impact on morphological variation. Distribution 480–2003 m depth. South China Sea, Philippines, Indonesia, New Caledonia, Kermadec Island, New Zealand, SE Australia (O’Hara & Stöhr 2006; OBIS 2021). Genus Ophiacantha Müller & Troschel, 1842Published as part of Nethupul, Hasitha, Stöhr, Sabine & Zhang, Haibin, 2022, New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach, pp. 1-95 in European Journal of Taxonomy 810 (1) on page 47, DOI: 10.5852/ejt.2022.810.1723, http://zenodo.org/record/641952
Ophiomusa lymani
No full text<i>Ophiomusa lymani</i> (Wyville Thomson, 1873) <p>Figs 13A–G, 14</p> <p> <i>Ophiomusium lymani</i> Wyville Thomson, 1873: 174–175, fig. 33.</p> <p> <i>Ophiomusium lymani</i> – Koehler 1904: 58; 1922b: 411, pl. 86 figs 5, 7–9. — H.L. Clark 1911: 107–108; 1923: 364. — Matsumoto 1915: 289. — Olbers <i>et al.</i> 2019: 72–74 fig. 51.</p> <p> <i>Ophiomusa lymani</i> – Hertz 1927: 103–105.</p> Material examined <p>CHINA • 1 spec.; South China Sea, E of Hainan Island, seamount; 18°24.45′ N, 114°52.09′ E; depth 1911 m; 12 Mar. 2020; collection event: stn SC005; MSV Shenhaiyongshi leg.; preserved in -80°C; GenBank: MZ 198762; IDSSE EEB-SW0008 • 1 spec.; South China Sea, SE of Hainan Island, seamount; 17°39.60′ N, 110°36.42′ E; depth 917 m; 1 Sep. 2017; collection event: stn SC015; MSV Shenhaiyongshi leg.; preserved in -80°C; GenBank: MZ 198763; IDSSE EEB-SW0009 • 1 spec.; South China Sea, SE of Hainan Island, seamount; 17°06.00′ N, 110°58.20′ E; depth 1500 m; 23 Mar. 2018; collection event: stn SC017; MSV Shenhaiyongshi leg.; IDSSE EEB-SW0034.</p> Remarks <p> We recorded three specimens from the South China Sea at 917 m to 1911 m depth. Disc diameter ranges from 17 to 20 mm. The specimens are similar to the holotype description by Wyville Thomson (1873) and to the first description from the South China Sea in Liao (2004) (Fig. 13A–G). The arm spine articulations are placed at the distal edge of the lateral arm plate (Fig. 14A–D). The vertebrae have a long zygospondylous articulation, a short, moderately large podial basin at the proximal end, and are small and narrow at the distal end. The dorsal end of the vertebrae is distally triangular and proximally flattened, with a long longitudinal groove along the midline, without furrow (Fig. 14E–H). The ventral end of the vertebrae has a broad midline longitudinal groove without an oral bridge (Fig. 14G). <i>Ophiomusa lymani</i> has been recorded from deep waters in both the East and South China Seas.</p> Distribution <p> 130–4829 m depth. East China Sea, South China Sea, Arabian Sea, Indonesia, Australia, New Zealand, Chile, Gulf of Mexico, Caribbean, Atlantic Ocean and South Africa (Olbers <i>et al.</i> 2019; OBIS 2021).</p>Published as part of <i>Nethupul, Hasitha, Stöhr, Sabine & Zhang, Haibin, 2022, New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach, pp. 1-95 in European Journal of Taxonomy 810 (1)</i> on page 28, DOI: 10.5852/ejt.2022.810.1723, <a href="http://zenodo.org/record/6419522">http://zenodo.org/record/6419522</a>
Ophiotreta eximia
No full textOphiotreta eximia (Koehler, 1904) Figs 15–16 Ophiacantha eximia Koehler, 1904: 116–117, pl. 21 figs 3–5. Ophiacantha dilecta Koehler, 1904: 117–118, pl. 22 figs 3–4. Ophiotreta eximia – H.L. Clark 1915: 216. — Koehler 1922a: 70–71, pl. 8 figs 5–6, pl. 93 fig. 7. — O’Hara & Stöhr 2006: 55–56, fig. 4e–g. Ophiotreta dilecta – H.L. Clark 1915: 216. — Koehler 1922a: 71. Material examined CHINA • 1 spec.; South China Sea, SE of Hainan Island, seamount; 17°35.80′ N, 111°02.00′ E; depth 1750 m; 3 Apr. 2018; collection event: stn SC022; MSV Shenhaiyongshi leg.; preserved in -80°C; IDSSE EEB SW0030. Description (IDSSE EEB-SW 0030) MEASUREMENTS. Disc diameter 11.9 mm, arm width 3.0 mm. DiSC. Circular, dorsal side covered by overlapping scales with one or mostly two spines (Fig. 15A–B). Disc spines tall, 0.4–0.6 mm high, 10–11 times as high as wide, slender, thorny, with two to three small, non-flaring terminal thorns (Fig. 15C–G). Few disc spines scattered on first dorsal arm segment (Fig. 15E). Radial shields covered by disc scales and skin (Fig. 15A, E). Ventral disc completely covered by disc spines, two small disc spines at ventralmost margins of three oral shields. Genital slits conspicuous, extending from oral shield to periphery of disc (Fig. 15B–F). Oral shield much wider than long, broadly triangular, with obtuse proximal angle and lobed or convex distal edge. Adoral shield long and narrow, mostly not separated. Adoral shields enclosing proximal edges of oral shield and separating it from first lateral arm plate, reaching just beyond lateral angle of oral shield (Fig. 15F). Jaws longer than wide. Cluster of papillae on jaw with three to five large, pointed, spiniform tooth papillae on dental plate and two rows of pointed papillae on apex of jaw (on oral plates), with large, pointed tip, five to seven lateral oral papillae and distalmost two flat and enlarged (Fig. 15F). ARMS. Dorsal arm plates as long as wide, fan-shaped, triangular with straight proximal end, slightly curved distal margin, covered with minute spines and consecutive plates completely separated (Fig. 15J). Ventral arm plates pentagonal, as wide as long except on first one to two arm segments, straight obtuse triangular proximal end, distal margin truncated to concave, along arm plates thickened distalwards, consecutive plates well separated (Fig. 15H–I). Lateral arm plates meeting above and below (Fig. 15H). 10–12 arm spines at each lateral arm plate; five to six upper arm spines four to six arm segments in length, smooth and meeting across dorsal midline (Fig. 15G); five to six lower arm spines short, two to three shortest, half arm segment in length, thorny (Fig. 15K). Lowermost arm spine on lateral arm segments slightly flattened with curved shape and straight, elongated thorns along tip of curved surface (Fig. 15H). One elongated, large tentacle scale with thorny apex, longer than ventral arm plate but becoming narrow and pointed distalwards on arm (Fig. 15K). First arm segment with two tentacle scales covering tentacle pore (Fig. 15F). COLOR. When alive, grey to whitish on disc and arms, mouth region and spines light brown (Fig. 15A–B). OSSiCLE MORPHOLOGY. Arm spine articulations well developed and placed at small angle in relation to distal edge of lateral arm plate, separated from proximal part of plate by wavy ridge. Ventral and dorsal articular lobes fused into a single volute-shaped articular structure (with sigmoidal fold, see Martynov 2010), dorsal lobe perforated by small holes, ventral lobe smooth and non-perforated (Fig. 16A). Large muscle opening and small nerve opening, but dorsalmost arm spine articulation without sigmoidal fold and ventral ones entire but connected to main part of lateral arm plate by short ridge (Fig. 16A–B). Vertebrae with long zygospondylous articulation, distally abruptly truncated, dorsal median furrow moderately expressed and podial basins long and large (Fig. 16C–G). Remarks The disc diameter of our specimen is within the range of the type specimens (11–21 mm). Koehler (1904) divided these specimens according to morphological variation of the arm plate and arm spines, but these variations fall within the morphological type series of O. eximia, and little morphological variation is expressed in the number of arm spines, height of the disc spines and number of oral papillae. The size of the specimens affects the morphological variation in O. eximia such as the number of oral papillae, the number of tentacle scales on the first arm segment and disc spine length. Due to these morphological variations, it is rather difficult to distinguish species of Ophiotreta. Ophiotreta matura Koehler, 1904 is quite similar to O. eximia , but differs in having stouter disc spines with flared terminal thorns, thornier upper arm spines and arm plates and hook-shaped thorny ventralmost arm spines (O’Hara & Stöhr 2006). The specimen in the present study showed a unique morphological feature in two small thorny spines located at the ventral margin of the oral shields directly proximal to the genital slits (Fig. 15F). Distribution 724–1893 m depth. South China Sea, New Zealand, Makassar Strait, Sulu Sea, Molucca Sea, Flores Sea, Coral Sea and Tasman Sea (O’Hara & Stöhr 2006; OBIS 2021). Genus Ophiopristis Verrill, 1899Published as part of Nethupul, Hasitha, Stöhr, Sabine & Zhang, Haibin, 2022, New species, redescriptions and new records of deep-sea brittle stars (Echinodermata: Ophiuroidea) from the South China Sea, an integrated morphological and molecular approach, pp. 1-95 in European Journal of Taxonomy 810 (1) on pages 31-34, DOI: 10.5852/ejt.2022.810.1723, http://zenodo.org/record/641952
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