Chone Krøyer, 1856

Tovar-Hernández, María Ana, 2008, Phylogeny of Chone Krøyer, 1856 (Polychaeta: Sabellidae) and related genera, Journal of Natural History 42 (33 - 34), pp. 2193-2226 : 2216-2219

Genus Chone Krøyer, 1856 , emended

Chone Krøyer, 1856, p.13 ; Sars, 1862, p.119; Malmgren, 1866, p.404; Langerhans, 1881, p.111; Hofsommer, 1913, p.332; McIntosh, 1923, p.287; Fauvel, 1927, p.334; Day, 1967, p.776; Banse, 1972, p.460; Fitzhugh, 1989, p.67; Giangrande, 1992, p.518; Tovar-Hernández and Sosa-Rodríguez, 2006, p.36 –37.

Parachonia Kinberg, 1867, p.355 .

Megachone Johnson, 1901, p.430 .

Metachone Bush in Moore, 1904, p.190.

Type species

Chone infundibuliformis Krøyer, 1856 , by original designation (redescribed by Tovar- Hernández and Sosa-Rodríguez 2006).

Emended diagnosis

Large-bodied sabellin species. Branchial lobes fused dorsally. Radiolar skeleton with two rows of cells. Palmate membrane and radiolar flanges present. Dorsal lips broadly rounded, as long as wide, without mid-rib, vascularized by plexus of small blood vessels derived from basal branchial blood vessels; dorsal lips with hyaline cartilage, but without branchial skeleton extensions. Longest pinnules at midradiole. Ventral lips present, broadly rounded. Dorsal and ventral pinnular appendages present. Anterior peristomial ring lobe entire, triangular or digitiform. Posterior peristomial ring collar present. Narrow, glandular ridge on chaetiger 2. Ventral shields absent. Notopodia in chaetiger 1 with two groups of elongate, narrowly hooded chaetae in C-shaped arrangement. Notopodia in chaetigers 2–8 with superior group of chaetae in two irregular rows, all elongate, narrowly hooded; inferior group with one anterior row of short bayonet chaetae, two posterior rows with symmetrical, mucronate (or with very fine hairs instead) paleate chaetae. Thoracic neuropodia bearing acicular uncini with teeth above main fang unequal in size, median tooth of basal row enlarged, hood present, handles long. Dentition of thoracic uncini occupying one-quarter of the main fang length. Anterior abdominal segments with two transverse rows of elongate, narrowly hooded chaetae, chaetae from the anterior row shorter than chaetae in posterior row; uncini with welldeveloped rectangular breast, handles absent, main fang well developed, few rows of small teeth covering one-quarter of the main fang length; intrafascicular variation: older uncini, located dorsalmost in torus, smallest in size, younger uncini, located ventralmost in torus, biggest in size. Posterior abdominal segments with very elongate, narrowly hooded chaetae; uncini shape and intrafascicular variation similar to those in anterior abdominal segments.

Remarks

The following genera have been placed into synonymy with Chone : Parachonia , by Johansson (1927); Megachone , by Banse (1972); Metachone , by Fauvel (1927); Dialychone , by Fitzhugh (1989). Parachonia letterstedti [ SMNH 576, holotype], Megachone aurantiaca [ MCZ 1933, holotype] and Metachone mollis [ YPM 2793, holotype]. All these genera fully conform to the above definition of the genus, except for Dialychone , which is re-established below.

The diagnosis provided here mostly follows Tovar-Hernández and Sosa-Rodríguez (2006); the emendation is restricted to emphasize that the species in Chone having an anterior peristomial ring lobe entire, triangular or digitiform; a narrow glandular ridge on chaetiger 2; and thoracic uncini with a median tooth of basal row enlarged which dentition covering one-quarter of the main fang length. The monophyly of Chone is based on the following synapomorphies: (1) dorsal lips broadly rounded; (2) thoracic uncini with a large tooth above the main fang, located in midline; and (3,4) thoracic and anterior abdominal uncini with dentition extending one-quarter of the main fang length. Currently, Chone comprises 12 nominal species: C. aurantiaca , C. costulata , C. duneri , C. fauveli , C. gracilis , C. infundibuliformis , C. kroyerii , C. letterstedti , C. magna , C. mollis , C. picta , C. rosea and one species not named formally: Chone sp. Aleutian Islands fide Tovar-Hernández (2007b) .

Genus Dialychone Claparède, 1870 re-established

Dialychone Claparède, 1870, p.170 ; Lo Bianco, 1893, p.77.

Type species

Dialychone acustica Claparède, 1870 , by original designation (redescribed by Tovar- Hernández et al. 2007).

Diagnosis

Medium to large-bodied sabellin species. Branchial lobes fused dorsally. Radiolar skeleton with two rows of cells. Palmate membrane and radiolar flanges present. Dorsal lips elongate, longer than wide, without branchial skeleton extensions. Ventral lips present, broadly rounded. Dorsal pinnular appendages absent. Ventral radiolar appendages present. Longest pinnules at mid-radiole. Anterior margin of anterior peristomial ring triangular or bilobed. Posterior peristomial ring collar present. Glandular ridge on chaetiger 2 narrow, broad dorsally, broad ventrally, broad with vertical projections, or hypertrophied. Ventral shields absent. Notopodia in chaetiger 1 with two groups of elongate, narrowly hooded chaetae in C-shaped arrangement. Notopodia in chaetigers 2–8 with superior group of chaetae in two irregular rows, all elongate, narrowly hooded; inferior group with one anterior row of short bayonet chaetae, two posterior rows with symmetrical, mucronate paleate chaetae. Thoracic neuropodia bearing acicular uncini with teeth decreasing gradually in size away from the main fang; dentition covers one-half of the main fang length; hood present, handles long. Glandular ridges on posterior thoracic segments can be present. Anterior abdominal segments with two transverse rows of elongate, narrowly hooded chaetae, chaetae from the anterior row shorter than chaetae in posterior row; uncini with well-developed rectangular breast, handles absent, main fang well developed with a series of teeth of nearly uniform size covering one-half of the main fang length; intrafascicular variation: older uncini, located dorsalmost in torus, smallest in size, younger uncini, located ventralmost in torus, biggest in size. Posterior abdominal segments with very elongate, narrowly hooded chaetae; modified uncini with hooked breast, handles absent and dentition covering threequarters of the main fang length; intrafascicular uncinal variation similar to those in anterior abdominal segments. Glandular ridges on anterior abdominal segments can be present. Pre-pygidial depression simple.

Remarks

Dialychone was synonymized with Chone by Fitzhugh (1989) on the grounds that the presence or absence of the palmate membrane is a character used to distinguish species rather than genera. Although no type material is available for this species, Knight-Jones et al. (1991), Giangrande (1992) and Fitzhugh (1989) reviewed topotype material of D. acustica , indicating that a low web extends for about onequarter of the branchial crown length. Later, Tovar-Hernández et al. (2007) recognized the synonymy proposed initially by Fitzhugh (1989) and designated a neotype and neoparatype for C. acustica (MNCN) . The description provided by Tovar-Hernández et al. (2007) emphasizes the presence of posterior abdominal uncini modified from those in the anterior abdomen; however, no distinction among anterior and posterior abdominal uncinal dentition was made. They emphasized that C. acustica could belong to a different genus based upon the modified, posterior abdominal uncini and the very elongate dorsal lips. In the present study, the genus Dialychone is re-established being monophyletic on the basis of lacking dorsal pinnular appendages, and by having teeth decreasing gradually in size away from the main fang in thoracic uncini.

Dialychone differs from Chone by the relative size of teeth in thoracic uncini because they decrease gradually in size away from the main fang, while they are unequal in size, median tooth of basal row enlarged in Chone ; by the lack of dorsal pinnular appendages which are present in Chone ; by having a pre-pydidial depression, which is missing in Chone ; and by having posterior abdominal uncini modified as Amphicorina - type, and not modified as in Chone .

Besides the type species, Dialychone includes 14 newly combined species: D. acustica ; D. albocincta n. comb.; D. arenicola n. comb.; D. australiensis n. comb.; D. collaris n. comb.; D. dunerificta ( Tovar-Hernández et al. 2007) n. comb.; D. longiseta n. comb.; D. normani n. comb.; D. perkinsi n. comb.; D. quebecensis n. comb.; D. trilineata n. comb.; D. trilobata (Gallardo, 1968) n. comb.; D. usticensis n. comb., and D. veleronis n. comb.