Pycnoderma gracilis Hartman 1961, n. comb.
Creators: name: Salazar-Vallejo, Sergio I.
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Terebellida
Flabelligeridae
Pycnoderma
Pycnoderma gracilis

description: Pycnoderma gracilis (Hartman, 1961) n. comb.
Figure 19
Piromis gracilis Hartman, 1961:123 –124, Pl. 29, Figs. 1–4, Pl. 30, Figs. 1–9 (partim).
Material examined. Eastern Tropical Pacific. Holotype (LACM-AHF-529) and paratype (LACM-AHF-530), off San Jose Light, Guatemala, R/V Velero III, Sta. 930 (13°52ʹ35ʺ N, 91°01ʹ0 2ʺ W), 12–13 fathoms, 23 Mar. 1939.
Additional material. One almost complete specimen (LACM-AHF-2517), R/V Velero I II, Sta. 216 (00°35ʹ50ʺ N, 80°07ʹ0 0ʺ W), San Francisco Bay, Ecuador, 20 fathoms, 11 Feb. 1934. Anterior fragment (LACM-AHF-2518), R/V Velero III, Sta. 930 (13°52ʹ35ʺ N, 91°01ʹ0 2ʺ W), off San Jose Light, Guatemala, 12–13 fathoms, fine black sand, 23 Mar. 1939. Four specimens (MCZ-55893, three; MCZ-55984, one), Gulf of Nicoya Benthic Survey, Sta. 24 (09°49ʹ25ʺ N, 84°41ʹ20ʺ W), 11 m, 1 Oct. 1980, H. Dean, coll.
Description. Holotype an anterior fragment (Fig. 19 A), laterally dissected previously; body cylindrical, slightly tapering posteriorly. Tunic thick, papillated, with many sediment particles; papillae long in anterior chaetigers, notopodial ones making large, truncate, conical lobes directed forwards (Fig. 19 B). Dorsum and venter with two longitudinal rows of long papillae, protruding through tunic, not forming large lobes. Holotype 20 mm long, 3 mm wide, cephalic cage 3 mm long, 29 chaetigers.
Anterior end not exposed, previously dissected (Fig. 19 D). Prostomium low cone, eyes small, dark brown. Caruncle long, well-developed, separating branchial lobes. Palps long, darker dorsally, palp keels rounded. Branchiae cirriform, distally dark, arising from tongue-like protuberance, with over 80 filaments per side. Some branchiae longer, others shorter, or as long as palps.
Cephalic cage chaetae as long as body width. Chaetigers 1–4 involved in the cephalic cage; chaetae arranged in a short row, chaetal fascicles dorso- and ventrolateral with 7–8 noto- and 5–6 neurochaetae per bundle. Anterior dorsal margin of chaetiger 1 with median trifid lobe, projecting anteriorly. Anterior chaetigers with long notopodial lobes, no large median papillae involved. Chaetigers 1–3 of similar size, notopodial lobes larger in chaetiger 3. Chaetal transition from cephalic cage to body chaetae gradual; bifid neurohooks from chaetiger 28, inconspicuous. Gonopodial lobes not seen.
Parapodia well developed, especially in anterior chaetigers, positioned at body corners. Median neuropodia ventrolateral. Notopodia with several long, cirriform, capitate papillae; papilla of anterior chaetigers forming large dorsal lobe, in median chaetigers forming postchaetal fans each with 4–5 papillae, intermediate papillae longer. Neuropodia smaller, with similar postchaetal papillae, in a fan with 3–4 papillae.
Median notochaetae arranged in longitudinal row, as lateral fan with 8–10 chaetae per bundle, each chaeta 1/3 as long as body width; all notochaetae multiarticulated capillaries with short articles basally and distally, long articles medially (Fig. 19 F). Neurochaetae multiarticulated hooks in two sizes, longer in anterior chaetigers (Fig. 19 G), shorter, bifid ones from chaetiger 28 (Fig. 19 H), mostly with broken tips, arranged in transverse row, directed forward in holotype, six per bundle, three of each size group, continued to end of body (Fig. 19 I).
Holotype without posterior end (Fig. 19 A, C); one paratype complete, posterior end conical, anus terminal (Fig. 19 E), without anal cirri.
Variation. One complete specimen (Sta. 216) has variable segment length: chaetigers 1–12 are medium sized, chaetigers 13–28 are short, and thereafter are elongated (or badly preserved) from chaetiger 28. One of the specimens that was included in the original description (station 767) does not belong to this species; it has straight neurohooks with very short anchylosed articles throughout the body, and three longitudinal series of black papillae; it is an undescribed species of Trophoniella.
Remarks. As stated above, Piromis includes only species with bifid multiarticulated neurohooks. After an examination of different specimens from the type locality, it was determined that because of the presence of neurohooks with few or very few articles in posterior chaetigers, Piromis gracilis does not belong in the genus Piromis. These specimens are extremely similar to the holotype and are regarded as conspecific; further, because they have neurohooks with a single long article in posterior chaetigers, consequently, the species has been transferred to Pycnoderma.
Pycnoderma gracilis (Hartman, 1961) n. comb. resembles P. glasbyi n. sp. (see above) because both have their body covered by small sediment particles. They differ because P. gracilis has dorsal lobes along a few anterior chaetigers, the sediment particles are densely packed, and the posterior neurospines are bidentate, whereas P. glasbyi n. sp. lacks dorsal lobes, the sediment particles are sparse and the posterior neurospines are bifid.
Distribution. The type material comes from two localities in the Eastern Tropical Pacific, from Guatemala and Ecuador, in 20– 40 m.
description: Published as part of Salazar-Vallejo, Sergio I., 2011, Revision of Piromis Kinberg, 1867 and Pycnoderma Grube, 1877 (Polychaeta: Flabelligeridae), pp. 1-50 in Zootaxa 2819 on pages 41-42, DOI: 10.5281/zenodo.277211