Juga H. Adams & A. Adams, 1854

Strong, Ellen E., Garner, Jeffrey T., Johnson, Paul D. & Whelan, Nathan V., 2022, A systematic revision of the genus Juga from fresh waters of the Pacific Northwest, USA (Cerithioidea, Semisulcospiridae), European Journal of Taxonomy 848, pp. 1-97 : 10

Genus Juga H. Adams & A. Adams, 1854

Vibex (Juga) H. & A. Adams, 1854 .

Type species: Melania silicula A. Gould, 1847 , by subsequent designation ( Baker 1963: 35).

Juga (Calibasis) D.W. Taylor, 1966 .

Type species: Melania (? Goniobasis) acutifilosa Stearns, 1890 , by original designation. Syn. nov.

Juga (Oreobasis) D.W. Taylor, 1966 .

Type species: Melania newberryi I. Lea, 1860 , by original designation.

Juga (Idabasis) D.W. Taylor, 1966 †.

Type species: Juga chrysopylica D.W. Taylor, 1966 †, by original designation. Syn. nov.

Diagnosis

Shell dextral, smooth to strongly plicate, lirate or cancellate, medium to large in size, ~ 1.5–3.5 cm in length. Operculum corneous, brown, paucispiral with eccentric nucleus. Gonochoristic, oviparous, with broad, shallow, triangular ovipositor pore; convoluted gonoductal groove, proximal albumen gland u-shaped; seminal receptacle present; tightly interlocking folds of lateral and medial laminae of prostate gland; gelatinous, finger-like egg masses with large numbers of eggs. Radula taenioglossate, rachidian basal cusps weakly developed or lacking. Midgut with comparatively narrow glandular pad and wide, shallow, crescentic groove; digestive gland duct vestibule receiving several ducts of digestive gland.

Remarks

Until recently, extant species of Juga were distributed among three subgenera, based on the sculpture of the early whorls ( Taylor 1966): Juga s. str. with strong and sometimes shouldered plications or ribs, Calibasis with spiral or lirate sculpture sometimes giving a frilled appearance, and Oreobasis with essentially smooth early whorls. Taylor (1966) also recognized a fourth subgenus with cancellate early sculpture, Idabasis , based on the Blancan fossil, Juga chrysopylica Taylor, 1966 . According to Frest & Johannes (2010: 7), Taylor further subdivided Oreobasis into two sections in an unpublished checklist dated from 1977 which we have not seen.

Strong & Frest (2007) synonymized Oreobasis with Juga s. str. given their morphological similarity in reproductive and alimentary anatomy. Campbell et al. (2016) concluded that none of the three extant subgenera were monophyletic but that clades of equivalent rank merited recognition. The molecular analysis of Strong & Whelan (2019) confirmed that the strength and persistence of spiral and axial sculpture are variable within and between species, sometimes among conspecific individuals at a single site, and that subgeneric designations based primarily on shell sculpture are not meaningful. Moreover, the molecular phylogeny did not reveal clades that would merit recognition at the rank of subgenus. Thus, we here further synonymize Calibasis and Idabasis with Juga .