Orbinia orensanzi, Blake, James A., 2017

Blake, James A., 2017, Polychaeta Orbiniidae from Antarctica, the Southern Ocean, the Abyssal Pacific Ocean, and off South America, Zootaxa 4218 (1), pp. 1-145 : 86-89

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https://doi.org/ 10.5281/zenodo.245827

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Orbinia orensanzi

new species

Orbinia orensanzi new species

Figures 40–41 View FIGURE 40 View FIGURE 41

Material examined. Argentina, intertidal, sand beaches, coll., J. M. Orensanz: Golfo San Matías, Las Grutas, 14 Jan 1973, 4 paratypes ( USNM 1013910 View Materials ) ; Golfo Nuevo, Golfo San José, San Ramon , 17 Nov 1975, holotype and 2 p aratypes ( USNM 1013908–9 View Materials ) ; 17 Feb 1975, 2 paratypes (USNM 1013911).

Description. All specimens posteriorly incomplete; holotype from San Ramon 10 mm long, 1 mm wide for 60 setigerous segments; paratypes from Las Grutas larger, up to 30 mm long, 1.2 mm wide for 95 setigerous segments. Body depressed in thoracic region; abdominal segments cylindrical. Thorax with 17–24 setigerous segments, with largest specimens having more thoracic setigers; at least 1–2 segments transitional. Color in alcohol: light brown, with white-colored sub-neuropodial abdominal flanges.

Prostomium conical, acutely pointed on anterior margin ( Fig. 40 View FIGURE 40 A); no eyespots; nuchal organs not observed. Peristomium reduced, fused to setiger 1; proboscis with 3–4 lobes.

Thoracic setigers all similar. Thoracic notopodia with postsetal lobes from setiger 4–5, lobes short at first, becoming cirriform in middle and posterior thoracic segments ( Fig. 40 View FIGURE 40 A, C–D), continuing on following abdominal setigers ( Fig. 40 View FIGURE 40 E–F). Largest specimens with distinct interramal cirrus in posterior thoracic setigers, first present from about setiger 18–19 ( Fig. 40 View FIGURE 40 D); interramal cirrus absent in abdominal segments. Thoracic neuropodia reduced to low thickened ridge from which setae emerge ( Fig. 40 View FIGURE 40 B–C); postsetal lobes present from medial posterior edge of setiger 3–4, short at first, becoming larger, triangular-shaped cirri by setiger 10–11 ( Fig. 40 View FIGURE 40 C); last 1–4 thoracic setigers with two postsetal lobes and 1–9 subpodial lobes on each side, forming distinct ventral fringe ( Fig. 40 View FIGURE 40 B, D) continuing through 3–7 abdominal setigers ( Fig. 40 View FIGURE 40 B); all subpodial lobes cirriform, expanded basally; numbers of segments with subpodial lobes dependent upon size, larger specimens with more. Abdominal parapodia elevated dorsally on large fleshy parapodial cushion ( Fig. 40 View FIGURE 40 E); neuropodia bilobed with inner lobe or dorsal cirrus shorter; outer lobe or ventral cirrus longer ( Fig. 40 View FIGURE 40 E–F); fleshy subpodial flanges present, with medial notch ( Fig. 40 View FIGURE 40 E–F).

Thoracic notosetae all crenulated capillaries ( Fig. 41 View FIGURE 41 D); abdominal notosetae including crenulated capillaries ( Fig. 40 View FIGURE 40 L) and furcate setae ( Fig. 40 View FIGURE 40 J); furcate setae with bifid-tipped unequal tynes connected by thin webbing composed of very fine needles ( Fig. 40 View FIGURE 40 J), with SEM individual needles tapering to fine tip, tips of tynes flattened, with distinct opening ( Fig. 41 View FIGURE 41 E); shaft smooth, transverse rows of barbs not apparent. Thoracic neurosetae with 4– 5 more or less vertical rows of uncini ( Figs. 40 View FIGURE 40 B, 41A–B); with companion crenulated capillaries in superior position of last row ( Figs. 40 View FIGURE 40 B–D, 41A–B), some posterior thoracic setigers with a few additional capillaries in middle of neuropodium ( Figs. 40 View FIGURE 40 D, 41B); uncini of setigers 1–4 thinner, more delicate than those on following thoracic setigers, where thick, heavy uncini in superior locations grade ventrally to thinner ones ( Figs. 40 View FIGURE 40 B–C, 41A); thickest uncini with blunted tip, curved convex side flattened, then grading into 3–4 prominent transverse ribs on convex curvature, rest of shaft smooth; ribs most prominent on anteriormost uncini ( Figs. 40 View FIGURE 40 G–H, 41A–C), thin uncini smooth or with transverse ribs weakly developed ( Fig. 40 View FIGURE 40 I). Abdominal neurosetae include 3–4 flail setae ( Fig. 40 View FIGURE 40 K), a thin, imbedded acicula, and an occasional delicate, smooth capillary seta; flail setae with thickened shaft bearing delicate ribs and very thin, smooth, terminal extension piece ( Fig. 40 View FIGURE 40 K).

Branchiae from setiger 13–18, each elongated, expanded basally ( Figs. 40 View FIGURE 40 C, E–F).

Etymology. This species is named for the late Dr. José M. (Lobo) Orensanz, who generously allowed me to study his collections of Orbiniidae from Argentina and Uruguay, and who made significant contributions to the study of the polychaetes of Argentina and the Southern Ocean.

Remarks. Orbinia orensanzi n. sp. belongs to a small group of species having branchiae from segments posterior to setigers 5–6, including O. hartmanae Day, 1977 from eastern Australia, O. riseri ( Pettibone, 1957) from eastern North America and O. johnsoni ( Moore, 1909) from western North America. Of these, only O. riseri and O. orensanzi n. sp. have interramal cirri. In O. riseri , the interramal cirrus is present in abdominal parapodia, whereas in O. orensanzi n. sp. they are present only in thoracic parapodia. A distinct ventral cirrus, present in O. riseri , is lacking in O. orensanzi n. sp. Thoracic neuropodial uncini are all smooth in O. hartmanae , ribbed and smooth in O. orensanzi n. sp., and ribbed with hoods in O. riseri and O. johnsoni .

Distribution. Argentina, intertidal in sand beaches.


Smithsonian Institution, National Museum of Natural History