Bhawatsonia fusa

Description. Based on the holotype: complete with 74 segments. TL = 8 mm, TW = 1.8 mm. Body stiffed, long, narrowed posteriorly (Fig. 14 A). Body orange to brown, dorsal and ventral cirri bases darker (Fig. 14 G). Paleae fan bright maroon to golden, non-imbricated dorsally. Prostomium retracted among the first four segments. Lateral antennae long, inserted on antero-ventral prostomial margin, median antenna slightly shorter than lateral ones, inserted in front of anterior eyes. Eyes red-violet, two pairs. Nuchal organ, semicircular nuchal fold, partially covering prostomium (Fig. 14 B, D). Palps short, ovoid, visible only in ventral view. Mouth fold small, placed between segment 3 and 4 (Fig. 14 C, E). Pharynx eversible, not exposed, stylet thick. Parapodium from segment 49, notochaetae in three main groups (Fig. 14 H). Notochaetae: lateral group inserted below notaciculum, 1 paleae, very slender and symmetrical, with 1 – 2 (3) internal ribs (Fig. 14 I); subunit 1, 1 palea, slender and symmetrical, with 9 – 10 (11) internal ribs (Fig. 14 J). Main group, 7 – 9 paleae, broad and symmetrical, with (14) 15 – 18 (20) internal ribs and 4 – 5 finely raised ribs (Fig. 14 K). Median group, 3 paleae, shorter, slender and asymmetrical; the distal-most palea with 10 – 11 internal ribs and 3 raised ribs; the next proximal palea smaller with (8) 10 internal ribs and 1 raised rib, and the proximal-most and smallest with 8 internal ribs and 1 raised rib (Fig. 15 A – B). All paleae with serrated margins. Neuropodium conical, smaller than notopodium. Neurochaetae: unit 1, 2 superior spinigers, blades straight and long, 15 – 16 times longer than wide (Fig. 15 C). Unit 2, 6 falcigers with blades straight and short, 1 – 2 times longer than wide (Fig. 15 D). Unit 3, 4 falcigers with blades straight and short, 2 times longer than wide (Fig. 15 E – F). Unit 4, 2 falcigers with blades straight and medium-sized, 5 – 6 times longer than wide (Fig. 15 G). Blades bidentate, bent distally. Pygidium conical with two anal cirri (Fig. 15 H). Oocytes not seen. Habitat. Subtidal (2 – 4 m). Specimens of this species were collected mainly on rocks, and as epibionts of bivalves.

Figs 14 – 15, 26 LSID: urn: lsid: zoobank. org: act: 2 F 7115 F 8 - 50 BE- 4897 - A 849 - 4 ADC 85 C 2860 F

Remarks. Bhawatsonia fusa n. sp., along with Bhawatsonia sp., belongs to the Bhawatsonia n. gen. members with broad main paleae and slender median paleae. Specimens of those species can be differentiated by the form of the main paleae; in B. fusa n. sp. specimens have broader main paleae, whereas specimens of Bhawatsonia sp. have slightly slender main paleae. In addition, subunit 1 appears to be taxonomically relevant in the members of the new genus. Specimens of B. fusa n. sp. have the subunit 1 with a rounded tip, and a range of internal ribs of 9 – 10, maximum of 12; whereas, specimens of Bhawatsonia sp. have the subunit 1 with an acute tip, and a range of internal ribs of 12 – 13, maximum of 14. Occurrence with specimens of B. purpurea n. comb. is common; however, both species are different. Bhawatsonia fusa n. sp. possess subunit 1 broad, with slightly higher rib number, 9 – 10, maximum 11; while B. purpurea n. comb. possess subunit 1 slender, with 8 – 10 internal ribs. Further, the main paleae of B. fusa n. sp. is clearly broader and shorter with slightly reduced rib number, 15 – 18, maximum 20 internal ribs; meanwhile, B. purpurea n. sp. possesses slender and longer main paleae with 17 – 18, maximum 23 interna ribs.

Distribution. From Bahía de los Ángeles, Baja California to Barra de Navidad, Jalisco (Fig. 26).

Etymology. The specific epithet is made after the Latin singular adjective fusa (- us, - um) meaning ‘ broad’. The name indicates the broad shape of upper middle section of the main paleae, and it is feminine for matching the genus gender (ICZN 1999, Art. 32.2).

Type locality: Aticama, Nayarit, México. Type material. Holotype: ECOSUR- 263, Aticama, Nayarit, México, northern Mexican Pacific, on bivalve, 2 m, November 25, 2004. Paratype: ECOSUR- 264, same as holotype. Other material examined. Six specimens. Baja California: ECOSUR- 3219, 2 spec. Bahía de los Ángeles, May 25, 1986, coll. SSV. Baja California Sur: ECOSUR- 3220, El Presidente, La Paz Bay, October 4, 1987, coll. SSV & ALG; ECOSUR- 3221, 2 spec. El Presidente, La Paz Bay, October 10, 1987, coll. SSV. Jalisco: ECOSUR- 3222, 2 spec. Barra de Navidad, on rock, 4 m, December 3, 2004, coll. BY & PSS.