Hydrobioides Nevill, 1885

Hydrobioides Nevill, 1885: 42.

Paranerita Annandale, 1920: 4 .

Parabithynia Pilsbry, 1928, syn. nov.: 108.

Bithynia (Parabithynia) – Popova et al. 1970: 95.

Type species.

Fairbankia turrita Blanford, 1869 (original designation; Myanmar, Irrawaddy River, “ Kyoukpong ”).

Diagnosis.

Shell medium for the family, solid, aperture lip thickened, outer lip outward extended; penial appendix located in the central of penis, penial appendix slightly shorter than distal part of penis.

Remarks.

According to Molluscabase (2024 a), there are six extant valid species assigned to this genus; five species are described from Myanmar, and one species is described from Laos. The type species of this genus is Hydrobioides turrita (Blanford, 1869) with high spiral whorls and an extremely outward extended outer lip (Fig. 3 P); its type locality is “ Kyoukpong ” near the Irrawaddy River in Myanmar (probably referring to Kyouk Pon near Bagan in the Mandalay Region), and it was also collected from Heho near the Inle Lake basin as subfossils (Annandale 1918). However, this species has never been collected again since Annandale (1918). Based on shell characters of Hydrobioides turrita, we consider that the outward extended outer lip is the most important morphological diagnosis character for this genus. Hydrobioides nassa is always considered widely distributed in north to central Thailand, but we consider that the Thai population should be another species (see in remarks of Hydrobioides nassa). We consider that Parabithynia Pilsbry, 1928, should be a synonym of Hydrobioides (see in remarks of Hydrobioides physcus). The molecular study based on 16 S and COI does not support Hydrobioides as a monophyletic group (Fig. 2). The taxonomy of this genus needs systematic revision.