Truncatoflabellum paripavoninum (Alcock 1894)

Truncatoflabellum paripavoninum (Alcock, 1894)

Flabellum pari–pavoninum Alcock, 1894:187.

Flabellum paripavoninum.—Alcock, 1898:21, pl. 2: figs. 3a,b.—Faustino, 1927:46–47, pl. 2: figs. 3, 4 [in part: ALB-5548,5648,5658, 5656, 5586, and USNM 40721].

Flabellum sp. Alcock, 1902a:31 [in part: Siboga 316].

Not Flabellum pavoninum.—Gardiner, 1902a:123–125.

Not Flabellum pavoninum var. paripavoninum.—Vaughan, 1907:59–62 [= F. vaughani].—Umbgrove, 1938:264 [= Flabellum sp.].—Yabe and Eguchi, 1942a:91–93, pl. 5: figs. 7, 8 [= F. lamellulosum and F. politum]; 1942b:129–130, pl. 11: fig. 9 [= F. politum].—Utinomi, 1965:255 [= F. vaughani].

Not Flabellum paripavoninum.—Vaughan, 1919, pl. 12: figs. 12, 12a [= F. vaughani].—Squires. 1964a:15 [= F. vaughani].—Wells, 1984:214–215, pl. 4: figs. 6, 7.

DESCRIPTION.—Angle of thecal edges variable, ranging from 65° to 135°; inclination of thecal faces 32°–62°. Largest anthocyathus examined (ALB–5283) 49.1 × 36.1 mm in calicular diameter and 41.0 mm tall. Upper calicular edge highly convex. Thecal edge spines absent; instead, the relatively short thecal edges meet at an acute angle, often producing a low edge carina. Basal scar variable in size, ranging from 6.8×4.1 to 14.5 × 6.8 mm. Anthocaulus 12.0 mm tall at point of fracture, with a pedicel diameter of about 1.7 mm, and a greater calicular diameter equal to that of the anthocyathus basal scar (in the single case known (ALB-5658), 11.5 mm). Illustrated fused anthocaulus plus anthocyathus (Plate 38a) 17.1 mm, the incipient line of fracture about 5 mm below calicular margin. Upper thecal edges of anthocaulus slightly carinate. Anthocyathus delicate, the theca a very light reddish brown. Lateral faces of living specimens often encrusted with barnacles, bivalves, and mollusk egg cases. Ratio of GCD: LCD = 1.4–2.0.

Septa hexamerally arranged in six cycles according to the formula: S1–3>S4>S5>S6 (192 septa). Sixth–cycle insertion begins at a greater calicular diameter of about 26 mm; pairs of S7 occasionally present in half–systems adjacent to principal septa of large specimens. S1–3 have straight to slightly sinuous, vertical, thickened inner edges, which fuse and intermingle deep in the fossa to form a well–developed columella. S4 about size of S1–3, the inner edges of which only occasionally fuse with the columella. S5 about size of S4 and extend about distance down inner thecal edge. S6 width of S5 and extend only about to distance down inner theca. S7, when present, rudimentary and only several mm long. Upper, outer septal edges attenuate, joining theca in a smooth concave curve. Granules small and sparse, aligned in curved rows following the contour of the inner septal edge.

azooxanthellate

394-1450 m

bathyal