Anularya, 2015

Zhang, Le-Jia, Chen, Shi-Chao, Yang, Li-Te, Jin, Lei & Köhler, Frank, 2015, Systematic revision of the freshwater snail Margarya Nevill, 1877 (Mollusca: Viviparidae) endemic to the ancient lakes of Yunnan, China, with description of new taxa, Zoological Journal of the Linnean Society 174 (4), pp. 760-800 : 787-788

ANULARYA ZHANG & CHEN GEN. NOV.

Type species: Margarya mansuyi ( Dautzenberg & Fischer, 1905) .

Etymology: Contraction of ‘anula’ (Latin for ring) and ‘ Margarya ’, in reference to the elevated spiral keel and its similarity with genus Margarya .

Description

Shell large, up to nearly 90 mm in height; thick and solid; mostly with seven or eight whorls, including two whorls of protoconch, well-developed subsutural ramp or depression at upper portion of each whorl, except for the protoconch; sculpture variable, but generally with between three and five prominent keels or shallow rings on each whorl, lower keel always situated near suture, thus becoming nearly invisible on spiral whorls; sculpture without axial ribs, nodules, or accessories; spiral keels not extending onto umbilical area; aperture ovate; umbilicus small or absent.

Operculum corneous, ovate, thick, and solid, red brown or dark brown, with subcentral nucleus and concentric growth lines; nucleus smooth and thick; opercular scar very large, relatively rough, outside smooth, obviously thickened.

Radula with about 70–110 rows of teeth, each with one central tooth, one lateral tooth, and two marginal teeth on either side of it; central teeth with between three and five cusps, outer marginal teeth with between five and 11 cusps.

Body and mantle colour of living animals is grey or black with sparse big or small yellowish spots above ( Fig. 7F ). Foot comparatively small, with large opercular lobe. Female with two very short cephalic tentacles of equal length, about 4 mm long, whereas right cephalic tentacle of male thickened and elongated, about 8–10 mm long, modified as a penis and bent down, but with left tentacle the same as described for the female ( Fig. 7I ). Gonochoristic, prostate in male pale yellow, about 17 mm long, testis light yellow, about 15– 20 mm long. Gravid females retaining one or two developing juveniles in uterus, size at birth mostly exceeding 10 mm.

Comparative remarks

Anularya gen. nov. differs from Margarya and Tchangmargarya by having no sculpture in the umbilical area ( Fig. 6 ). It also differs by having a thicker and more solid operculum with smooth, thick nucleus, larger opercular scar, and more thickened outside area ( Fig. 8 ). Anularya gen. nov. resembles Heterogen Annandale, 1921 , endemic to Lake Biwa, Japan. It differs from Heterogen by having a ramp-like shoulder on upper portion of each whorl and the absence of a thicklayered opercular margin. Anularya gen. nov. also quite resembles Apameaus Heller & van Damme, 2006 , a fossil genus from the Jordan Valley ( Bridgland et al., 2012); however, Anularya gen. nov. has a much larger shell and smooth base of body whorl without any ribs, whereas Apameaus has several spiral ribs around the umbilicus. Moreover, Apameaus species retain more embryos (7.7 ± 6.4; Ashkenazi et al., 2010) than Anularya species (one or two) in gravid females. As for anatomical characters, Anularya gen. nov. differs from other genera in that the male cephalic right tentacle (penis) is longer than left tentacle and its outer marginal teeth have fewer cusps, as well as in body colour.

ANULARYA MANSUYI ( DAUTZENBERG & FISCHER,

Figures

Figure 6. Umbilical views of the shells: A, Margarya melanioides; B, Margarya monodi; C, Margarya francheti; D, Margarya oxytropoides; E, Tchangmargarya multilabiata sp. nov.; F, Tchangmargarya yangtsunghaiensis; G, Anularya bicostata; H, Anularya mansuyi. Margarya with several weak spiral ribs; Tchangmargarya with two strong nodular spiral ribs; Anularya gen. nov. without any sculpture.

Figure 7. Skin colour and morpholgy of cephalic tentacles: A, Margarya melanioides; B, Margarya francheti; C, Margarya oxytropoides; D, Margarya monodi; E, Tchangmargarya yangtsunghaiensis (offered by Jin Chen); F, Anularya bicostata; G, head of male Margarya species; H, head of male Tchangmargarya species; I, head of male Anularya species. Abbreviations: ey, eye; lt, left tentacle; pb, proboscis; pn, penis (right tentacle).

Figure 8. Operculum morphology (inner surface): A, Margarya oxytropoides; B, Margarya melanioides; C, Margarya monodi; D, Margarya francheti; E, Tchangmargarya yangtsunghaiensis; F, Tchangmargarya multilabiata sp. nov.; G, Anularya mansuyi; H, Anularya bicostata; I, Cipangopaludina chinensis. J, characters measured for morphological analysis of operculum: HO, height of operculum; HOS, height of opercular scar; WO, width of operculum; WOS, width of opercular scar.