Figure 18
Flabelligera mundata Gravier 1906:537–538; Gravier 1907:37–39, Pl. 4, Figs. 31–32, Text figs. 22–23; Gravier 1911:110–112, Pl. 8, Fig. 87 (partim); Benham 1921:108–109; Monro 1930:161; Monro 1939:130 (partim); Hartman 1952:233; Hartman 1953:50; Hartman 1966:37–39, Pl. 11, Figs. 1–4; Hartman 1967:124; Hartman 1978:170; Rozbaczylo 1985:159, Hartmann-Schröder & Rosenfeldt 1989:72; Knox & Cameron 1998:72, Figs. 137–139.
Type material. Antarctic Ocean. Syntypes of Flabelligera mundata (MNHN-561), off Port Charcot, Carthage Bay, R / V Français, Stat. 382, 40 m, 15 Apr. 1904, Turquet, coll. (larger syntype used for redescription; smaller one previously dissected, measured.
Additional material. Antarctica. Eight specimens (MNHN-A183), Port Foster, Deception Island, R/ V Pourquoi pas?, Stat. 742, 32 m, J. Liouville and L. Gain, coll. Two specimens (USNM-271533), Turtle Rock, Erebes Bay, McMurdo Sound Stat. 67-14, Carlton Ray coll., Oct–Nov. 1966. One small specimen (USNM-323383), USARP SOSC-BCF, R/V Hero 702 Stat. 447 (64°49'13" S, 63°30'03" W to 64°49'13" S, 63°30'15" W), Blake TR, 20– 27 m. Two specimens (LACM-AHF-540), off east side of Navy Island (68°13' S, 66°59' W), Southern Shetland Islands, 12–22 fathoms, 8 Mar. 1940, W.H. Schroeder coll. One specimen (SMNH-55734), damaged, Swedish South Polar Expedition 1901–03, Stat. 22 (54°17' S, 36°28' W), off Maya Bay, Cumberland Bay, South Georgia Islands, 75 m, clay and algae, 14 May 1902. One specimen (SMNH-55735), damaged, Swedish South Polar Expedition 1901–03, Stat. 17 (53°34' S, 43°23' W), Shag Rock Bank, between South Georgia and Falkland Islands, 160 m, sand and gravel, 19 May 1902. One specimen (SMNH-55736), damaged, Swedish South Polar Expedition 1901–03, Stat. 17 (53°34' S, 43°23' W), Shag Rock Bank, between South Georgia and Falkland Islands, 160 m, sand and gravel, 19 May 1902. One specimen (ZMH-8593), 1 Nov. 1902, 385 m.
Description. Larger syntype complete, pale (with oblique cut on right side of anterior end); body blunt anteriorly, posteriorly tapered, slightly depressed (Fig. 18A); 57 mm long, 14 mm wide, cephalic cage 4 mm long (barely 2 mm exposed), 25 chaetigers. Tunic thick, opaque (Fig. 18B), papillated, free from sediment particles; papillae long, distally fusiform, clavate, forming sheath around chaetae; papillae thinner in notochaetal than in neurochaetal shafts.
Cephalic hood not exposed. Anterior end observed in other specimens (LACM-AHF-540, USNM-271533). Prostomium low cone; four large red eyes. Caruncle well developed, two thick longitudinal keels and a shallow central area, separating the branchial plate into two lateral groups (Fig. 18D). Palps long, distally swollen (by compression of median and basal parts); palp bases large, rounded. Lip development modified by contraction; one heavily contracted specimen has lateral lips elongated, triangular; the other, less contracted, has large rounded lateral lips. Dorsal lip well developed, triangular; ventral lip bilobed.
Branchiae separated into two lateral groups; branchial filaments arranged in 6–7 rows, about 110 filaments per side, decreasing in size ventrally. Nephridial lobes in branchial plate, dotted, long, positioned below branchial group, at level of prostomium.
Cephalic cage chaetae about 1/15 body length or 1/7 body width (Fig. 18C). Chaetiger 1 involved in cephalic cage, 26–28 noto- and 22–24 neurochaetae per side. Anterior dorsal margin of chaetiger 1 smooth. Anterior chaetigers without especially long papillae. Chaetigers 1–3 of about the same length. Chaetal transition from cephalic cage to body chaetae abrupt; neurohooks from chaetiger 2. Gonopodial lobes not seen.
Parapodia well developed, lateral, completely covered by tunic. Median neuropodia ventrolateral. Notopodia arranged in groups with successive descending alignment (Fig. 18A, larger syntype); first in groups of two, then in groups of three to end of body. Arrangement (using u for upper, m for middle, and l for lower) starting with chaetiger 1: u, l, u, l, u, m, l, u, m, l … Noto- and neuropodia widely separated.
Median notochaetae in long papillary cylinders, all multiarticulated capillaries, three times as long as body width, 5–6 per fascicle, articulations restricted to far distal regions (Fig. 18E, insert). Neurochaetae multiarticulated capillaries in chaetiger 1; long, multiarticulated neurohooks from chaetiger 2, in cylindrical shaft, 3–4 per fascicle (Fig. 18F, G). Handle articulation distally placed, articles regular or of roughly the same length, becoming slightly longer distally; 12–17 articles, most medium sized, distal ones long. Other articles anchylosed, continued to bending region. Crest slightly wider than handle, dark yellowish along body, pigment extending towards base; width:length ratio 1:8.
Posterior end completely covered by tunic; pygidium with anus terminal, without anal cirri. Ova abundant behind palps in largest syntype.
Remarks. Flabegraviera mundata (Gravier, 1906) n. comb. resembles F. profunda n. sp. because both have thick tunics with very long chaetae. They differ because in F. mundata the tunic is generally free of sediment, all neurohooks have distinct crests and their handles are multiarticulated, whereas in F. profunda n. sp. the tunic is covered by sediment, and most neurohooks are completely anchylosed: not only the handles but the bending region in the crests is poorly defined, if visible at all.
Flabegraviera mundata n. comb. was described with 3–4 neurohooks per neuropodium, each with a regularly multiarticulated handle and an anchylosed articulation. Ehlers (1913) identified some small specimens as this species but they were had only a single hook per neuropodium. This feature might be size dependent.
Some specimens from deeper water (BMNH) had a bluish-gray coating (Benham 1927:129), which has been regarded as a preservation artifact (Augener 1918:452). However, this is a different species that is described below. Neurohooks are indeed of the same type as in shallower water forms. Deeper water forms may differ in several morphological features and in the proportion of neurohooks between anchylosed and multiarticulated, but the Terra Nova specimens fit F. mundata.
Distribution. The species was originally described from 40 m in Antarctic localities and is confirmed for depths of 20– 385 m.