Figures 4–6.
Etymology. This new species is dedicated to Professor T. Heinzeller Ludwig-Maximilian-University, Munich (Germany), who has contributed substantially to our understanding of crinoid anatomy.
Material examined. Holotype (catalogue number ZSM 0000/ 1) and one paratype (catalogue number ZSM 0000/ 2) R/V Polarstern cruise ANT IX/ 3, station 18 / 192, 27.02. 1991, off Queen Maud Land, 69 ° 40.3 ’ to 69 ° 40.5 ’ S –00° 51.1 ’ to 00° 54.8 ’ E, 1393–1398 m, housed in the Bavarian State Museum Collection of Zoology (ZSM) in Munich.
Diagnosis. A small species with robust arms of proximal pattern 1 + 2 3 4 5 + 6 7 + 8 or 5 + 6 7; beyond Br 6 series of successive brachial pairs (a+b c+d e+f…) or brachial pairs alternating with free brachials (a+b c d+e f...); series of up to 4 successive muscular articulations. Pinnules relatively robust and rigid; insertion deep, carved on arm side and impacting the following brachial pair; synarthrial articulation on brachial with strong symmorphy; concave cover plates varying from lanceolate to rounded; genital pinnules with one row of additional H-shaped plates. Ratio of primibrachial width to upper radial height 0.73 to 0.85. Tegmen with oral cone higher than anal cone; orals large and erect around mouth; anal cone conspicuous in C–D inter-ray and bearing large bulging plates. Conical dorsal cup with ratio of cup height to upper diameter 1 to1.3; basals fused; radials trapezoidal. Columnal symplexies with 8 crenular units; distal syzygies unknown.
Description of the holotype. Specimen consisting of proximalmost stalk, theca and partly broken crown (Fig. 4 A). Tegmen heavily plated and not inflated; tegminal plates of variable shape, some perforated by hydropores; anal cone height 2.8 mm, covered by relatively large bulging plates and conspicuous in C–D inter-ray (Fig. 4 B); oral cone height 3.6 mm with conspicuous, convex and smooth orals surrounding beak-like mouth (Fig. 4 C); ambulacral grooves merging into arms at height of Br 4. Aboral cup tall conical with large ribs prolonging arm axes; cup height 9.3 mm, upper diameter 7.2 mm, lower diameter 2.0 mm, ratio of cup height to upper diameter 1.3.
Radials trapezoidal, height 5.3 mm, upper width 3.7 mm, lower width 2.7 mm. Ratio of primibrachial width to upper radial height 0.73 to 0,77. Basals fused, height of basal ring 3.7 mm. Remaining proximal stalk 6.6 mm long, proximalmost diameter 1.7 mm.
One arm broken at Br 2–3, other arms with the same pattern: 1 + 2 3 4 5 + 6 7 + 8 9 + 10 11 + 12 13 + 14 15 16 + 17 18, with first pinnule on Br 4. Series of successive muscular articulations up to 3. Primibrachial width 2.7 mm decreasing progressively to 2.0 mm at Br 5 + 6. Most complete remaining arm 40 mm long and bearing 12 pinnules on each side. Pinnules relatively robust and rigid; width decreasing rapidly and progressively from proximal pinnular to distal end. Pinnule insertion deep, carved on arm side and impacting the following brachial pair (Fig. 4 D). Most complete pinnule (24 pinnulars) in medial arm reaching a length of 16.0 mm. Brachial synostoses flat (Fig. 4 E). Pinnule articulated on brachial by large transverse symmorphial synarthry with a deep ligament fossae (Fig. 4 F–G). First pinnular (p 1) with a sharply convex proximal facet (Fig. 5 A–B); p 1 and p 2 articulated by well-developed muscular synarthry (Fig. 5 B–D); other pinnulars articulated by synostoses (Fig. 5 E–F). Proximal part (up to p 12) of genital pinnules inflated, with H-shaped additional plates (Fig. 5 G–I) supporting a row of small upper lateral plates (Fig. 5 J–K); cover plates concave varying from lanceolated to rounded (Fig. 5 M–N).
Description of the paratype. Young immature specimen completely preserved except distal stalk and one arm broken at Br 9 + 10 (Fig. 6 A). Five relatively robust and smooth arms with 7–8 pinnules on each side; arm length about 19 mm with 27–28 brachials. Proximal pattern 1 + 2 3 4 5 + 6 7, with first pinnule on Br 4; successive muscular articulations up to 4. Primibrachial width 1.7 mm progressively decreasing to 1.0 mm beyond Br 5 + 6; distance between arm base and synostosis Br 5 + 6 3.9 mm. Pinnule length up to 8.9 mm for 17 pinnulars. Tegmen with large erect orals; oral cone height 1.8 mm, anal cone height 1.3 mm. Aboral cup with fused basals and trapezoidal radials, cup height 4.1 mm, upper diameter 4.0 mm, lower diameter 1.3 mm, ratio of cup height to upper diameter about 1. Basal height 1.6 mm, radial height 2.5 mm; lower radial width 1.6 mm, upper radial width 2.0 mm. Ratio of primibrachial width to upper radial width 0.85. Length of preserved stalk of 66 columnals 28.0 mm. Proximal most diameter 1.2 mm, decreasing to 0.8 mm at a distance of 2.8 mm from aboral cup and maintaining the same value to distal end. In distal half of preserved stalk, columnals barrel-shaped with height 0.6–0.7 mm. Columnal symplexies less developed, galleried stereom predominating with larger meshes around lumen; 8 small crenular units of 1 crenula near outer border (Fig. 6 B–C).
Remarks. F. heinzelleri n. sp. is a species smaller than F. aculeatus and F. k o s lo w i. It is distinguished by having a highly conical aboral cup, smooth convex orals, narrow inter-rays (ratio of primibrachial width to upper radial height> 0.7), anal cone with relatively large bulging plates and pinnules deeply inserted on arm side impacting the following brachial pair. Stalk articulations are only known in the proximal part of a juvenile specimen, without data on distal syzygies which usually bear specific characters (Améziane & Roux 2011). F. heinzelleri n. sp. shares with F. k o s l o w i the same pattern of proximal and mid-arm articulations with rare free brachials. These two species live at about the same depths, whereas F. a c u l e a t u s lives in deeper environments.
Occurrence. Antarctica slope, E of Weddell Sea, at a depth between 1393 and 1398 m.