Ptilocrinus (Chambersaecrinus) brucei Vaney

Ptilocrinus (Chambersaecrinus) brucei Vaney in Wilton, 1908 Figures 9–16, Tables 9–15. Synonymy: Ptilocrinus brucei Vaney in Wilton, 1908: fig. 70, pl. 23; Vaney & John, 1939: 661–664, 1 pl.; A.H. Clark, 1915: 161; Smaldon et al., 1976: 74; Roux, 1980b: 36, 41, 53, pl. 3 (figs. 5–6); Roux et al., 2002: 822. P. (Chambersaecrinus) brucei: Mironov & Sorokina, 1998: 52 –55, fig. 19–20, pl. 8 (figs. 4–5); Roux & Lambert, 2011: 45, 48, 51; Eléaume et al., 2014: 210–211. P. (Chambersaecrinus) flexibilis Mironov & Sorokina, 1998: 55 –57, fig. 21, pl. 11 (fig. 2). Holotype. NMS 1921.143.1743, S. Y. Scotia, sta. 301, NW Weddell Sea, 64°48’S – 44°26’W, depth 4,585 m (2,485 fms). Material examined. NHM 1939.5.13.1 (paratype), S. Y. Scotia, trawl 3426, off South Orcade Islands, 62° 10’S, 41° 20’ W, depth 3,245 m (includes note by D. John in 1938: specimen was “broken into small species but among them some individual plates, radials, etc.. are recognizable”.); USNM 1005433, South East Pacific basin, 63°0.3’to 63°12.0’S –128°12’ to 128°11’W, depth 4,682 m (2 specimens; 1 with theca, proximal arm and stalk; 1 juvenile with complete stalk, basal ring and fragments of proximal arms and radials); USNM 1005438, South Atlantic Ocean, Scotia Sea, South Georgia Island, 54°00’– 54°05’S, 33°40’– 33°43’W, depth 2663–2718 m (1, partly fragmented, theca poorly preserved, fragments of proximal arms with radials); USNM 1005439, South Atlantic, Scotia Sea, NE of South Shetland Islands, 59°S– 51.9°W, depth 3,010–3,510 m (1 theca, proximal arms and stalk fragments); USNM 1105453-A South Orkney Islands, Scotia Ridge, 62°09’ à 62°16’S –38°11’ à 38°24’W, depth 3,056–3,459 m (dissociated radials, basal ring, proximal brachials and proximalmost columnals). Emended diagnosis. A species of Ptilocrinus (Chambersaecrinus) reaching large size; proximalmost stalk diameter to 4.5 mm, arm length to 130 mm with about 40 pinnules on each side, and pinnule length to 55 mm. External morphology variable; ratio of cup height to adoral diameter 0.97–1.36; ratio of cup to radial height 1.01– 1.65 (usually 1.20–1.34); ratio of radial to first brachial width 1.45–1.97; ratio of adoral cup to proximalmost stalk diameter 3.25 (small specimen) to 4.27 (usually 3.97–4.20); arm deeply inserted on adoral radial edge; basal cup and proximalmost stalk diameter usually equal; maximum ratio of columnal height to diameter in a given stalk from 1.43 in smallest specimen to 0.41 in large specimens. Tegmen inflated and rounded; anal cone significantly taller than oral cone and reaching level of Br8 to Br 14 in large specimens; base of anal cone peripheral on tegmen; upper part of cone oriented toward tegmen center; orals smooth and concave with rounded top; as many as 20 large polygonal tegminal plates sometimes with a regular median arrangement. Arm pattern variable, from chiefly alternating free brachial and brachial pairs to long series (more than 20) of successive free brachials beyond the third brachial pair; proximalmost arm pattern 1+2 3 4 5+6 7 (75.9%), 1+2 3 4 5+6 7+8 (13.8%); first pinnule usually on Br4 (94.7%), rarely on Br5; most frequent brachial pairs beyond Br7 at 8+9 (44.0%), 10+11 (22.7%) and 18+19 (27.3%). Brachial muscular synarthry with conspicuous process prolonging adoral groove. Pinnule inserted on distal adoral side of brachial; proximal part with asymmetrical genital inflation; great number of additional small proximal plates decreasing distally; additional plates imbricated or irregularly aligned. Stalk symplexies with 6 (young stage) to 14 (usually 8–12) crenular units of 1 crenula of various lengths; up to 3 crenulae or subsidiary crenulae developed between units in large specimens; axial canal in proximal mesistele enlarges substantially during ontogeny; lumen bordered by coarsely-meshed galleried stereom; distal syzygies with thin irregular radial crenularium. Description. Tables 9 and 10 list biometric parameters, including holotype and paratype. The small number of specimens and the wide range of character variations preclude obtaining robust results from statistical analyses on the main changes in quantitative ratios during ontogeny. USNM 1005439: Theca well preserved with proximal and mid arms (Fig. 9 A–B) strikingly resembling the original figure of the holotype (Wilton 1908; Vaney & John 1939). Tegmen inflated and rounded; high anal cone reaching level of Br14, significantly taller than oral cone; base of anal cone peripheral on tegmen; upper portion of cone oriented toward tegmen center (Fig. 9 A–B); orals subvertical, smooth and concave with rounded tip; as many as 20 large polygonal tegminal plates without peculiar median arrangement in inter-rays (Fig. 9 B); inter-rays A–B, C–D, A–E wider than the two other inter-rays; hydropores on adoral quarter of tegmen; conspicuous ambulacral “bridges” between Br10–11 and top of oral cone with cover plates in a gathered arrangement; outer ramifications of “bridges” corresponding to proximal pinnules not attached to tegmen. Proximal arm pattern 1+2 3 4 5+6 7 (5 cases) with first pinnule on Br4; brachial pair at 8+9 (3 cases) and 9+10 (1); number of successive muscular synarthries beyond the last brachial pair and before broken end: 6 (2 cases), 8 (1), 24 (1), and 16 including Br7 (1). Two ossicles of a brachial pair united by flat synostosis. Pinnule socket in distal half of brachial adorally (Fig. 10 A–B); transverse muscular synarthry uniting pinnule to arm with marked fulcral ridge and deep muscular fossa on brachial (Fig. 10 E–F); free brachial with strongly oblique muscular articulations (Fig. 10 B); muscular synarthries with ambulacral groove forming a conspicuous adoral process in mid-articulation (Fig. 10 C–D). Adoral proximal arm inflated with numerous lateral plates not aligned, and conspicuous festooned cover plates in a gathered arrangement; proximal part of pinnules with proximal genital inflation of asymmetric, multiplated architecture, and cover plates poorly differentiated (Fig. 11 A–B); 3 (maximum 4) irregular plate rows on convex side decreasing to 1 row distally (Fig. 11 B); concave side without rows; lateral plates small or disappearing in mid arm with cover plates rounded or elliptical; muscular synarthries of first pinnular with brachial (Fig. 10 E) and with second pinnular (Fig. 11 E) having perpendicular fulcral ridge allowing wide amplitude of movements; symmetrical synostosis between second and third pinnular (Fig. 11 F–G); following pinnulars asymmetrical, supporting genital inflation (Fig. 11 H–I); pinnulars becoming more symmetrical distally. Length of proximal stalk attached to aboral cup 5.0 mm with 10 columnals; proximalmost diameter 3.4 mm; cup aboral diameter 3.4 mm; stalk distal diameter 3.0 mm. Stalk fragment with distal proxistele and transition to mesistele: length 17.05 mm with 22 columnals; proximal diameter 2.95 mm with maximum columnal height 0.9 mm, and symplexy with 11 crenular units of 2–3 crenulae (fig. 12 B–C); distal diameter 2.8 mm with maximum columnal height 1.6 mm and symplexy with 11 crenular units of 1 robust crenula (Fig. 12 D); inner areola and probably claustrum depressed proximally (diameter 1.3 mm), with round lacuna of diameter 0.5 mm; inner areola surrounded by coarsely-meshed stereom; stereom of depressed area progressively resorbed distally, resulting in a larger axial canal (diameter 1.0 mm) (Fig. 12 B–D); ratio of axial canal to columnal diameter in this fragment from 0.44 (proximal) to 0.36 (distal). USNM 1005438: Large specimen in fragments, lacking aboral cup: radials attached to arms, fragment of inflated tegmen and tall anal tube, and complete stalk except proximalmost columnals. Proximal arm pattern 1+2 3 4 5+6 7 8 with first pinnule on Br4 (5 cases), brachial pair at 9+10 (1), 10+11 (2), and no other brachial pair (1); fifth arm broken after Br8; mid arm with free brachial only; maximum number of muscular articulations before broken end 21; distal arm fragments rarely with one brachial pair; muscular articulations oblique beyond Br4; Br1 to Br3 with lateral wings. Height and width of brachials moderately decreasing from Br1 to Br3 and very little beyond Br3 (Table 11). Arms attached to tegmen to Br9; adoral face of arm inflated and multiplated, with festooned cover plates in a gathered arrangement; genital inflation of some pinnules with numerous imbricated irregular polygonal plates not in rows (Fig. 11 C), covering exceptionally preserved gonads with oocytes of 100– 150µ (Fig. 11 D); other pinnules with asymmetric architecture described above; arm and pinnule articulations as in previous specimen. Remaining stalk length 386 mm (five fragments without gap); Table 12 lists quantitative columnal parameters; columnal diameter increasing rapidly at distal end suggesting stalk broken close to attachment disk. Proximalmost columnal with 14 crenular units (poorly preserved); number of crenular units decreasing to 12 of one crenula in proximal mesistele (Fig. 13 A), to 11 with numerous subsidiary crenulae in mid mesistele (Fig. 13 B), and to multiradiate symplexy with initially 10 crenular units observed at center in distal mesistele (Fig. 13 C); transition symplexy/syzygy (Fig. 13 D) with development of syzygial stereom on facet surface (Fig. 13 E) indicating short dististele (30–40 mm) with anchylosed articulations; distalmost columnals with facet entirely covered by syzygial stereom, juvenile symplexial pattern of 6 small crenular units of 1 crenula and pentalobate lumen at center (Fig. 13 F). Axial lumen diameter to 1.8 mm proximally; ratio of lumen to columnal facet diameter 0.45 in proxistele and proximal mesistele, decreasing slowly to 0.25 in distal mesistele and rapidly to 0.09 in dististele. From distal proxistele to mid mesistele, axial canal surrounded by galleried stereom of large meshes bordering small deep ligamentary pits fused with lumen and alternating with crenular units (Fig. 13 G–H and J–K); pit floor corresponding

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