Bhawatsonia fusa, Cruz-Gómez, 2021

Bhawatsonia fusa View in CoL n. sp.

Figs 14–15 View FIGURE 14 View FIGURE 15 , 26 View FIGURE 26

LSID: urn:lsid:zoobank.org:act:

Bhawania sp. 3 .— Cruz-Gómez et al. 2021: 180, Fig. 5A View FIGURE 5 (key of chrysopetalids from Tropical America).

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 .

Description. Based on the holotype: complete with 74 segments. TL= 8 mm, TW= 1.8 mm. Body stiffed, long, narrowed posteriorly ( Fig. 14A View FIGURE 14 ). Body orange to brown, dorsal and ventral cirri bases darker ( Fig. 14G View FIGURE 14 ). 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. 14B, D View FIGURE 14 ). Palps short, ovoid, visible only in ventral view. Mouth fold small, placed between segment 3 and 4 ( Fig. 14C, E View FIGURE 14 ). Pharynx eversible, not exposed, stylet thick.

Parapodium from segment 49, notochaetae in three main groups ( Fig. 14H View FIGURE 14 ). Notochaetae: lateral group inserted below notaciculum, 1 paleae, very slender and symmetrical, with 1–2 (3) internal ribs ( Fig. 14I View FIGURE 14 ); subunit 1, 1 palea, slender and symmetrical, with 9–10 (11) internal ribs ( Fig. 14J View FIGURE 14 ). Main group, 7–9 paleae, broad and symmetrical, with (14) 15–18 (20) internal ribs and 4–5 finely raised ribs ( Fig. 14K View FIGURE 14 ). 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. 15A–B View FIGURE 15 ). 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. 15C View FIGURE 15 ). Unit 2, 6 falcigers with blades straight and short, 1–2 times longer than wide ( Fig. 15D View FIGURE 15 ). Unit 3, 4 falcigers with blades straight and short, 2 times longer than wide ( Fig. 15E–F View FIGURE 15 ). Unit 4, 2 falcigers with blades straight and medium-sized, 5–6 times longer than wide ( Fig. 15G View FIGURE 15 ). Blades bidentate, bent distally. Pygidium conical with two anal cirri ( Fig. 15H View FIGURE 15 ). Oocytes not seen.

Habitat. Subtidal ( 2–4 m). Specimens of this species were collected mainly on rocks, and as epibionts of bivalves.

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

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.

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).