Pachychilidae, common name pachychilids, is a taxonomic family of freshwater snails, gastropod molluscs in the clade Sorbeoconcha.

Distribution

Pachychilids are freshwater snails with a worldwide distribution in the tropics. Representatives are found in South and Central America, Africa, Madagascar, South and South-east Asia and tropical Australia (Queensland: Torres Strait Islands).

Description

Pachychilids have an operculum, which is concentric and multispiral.

Ecology

All species in the family inhabit freshwater except Faunus ater, which is a brackish water snail found in estuaries and other coastal habitats. Pachychilids are either oviparous (lay eggs), ovoviviparous or viviparous (retain developing eggs and youngs in special incubatory structures).

Notes on the taxonomy

The name is derived from a combination of the words 'pachy' (Greek = thick) and the suffix '-chilus' (Greek = Lip), meaning 'thick lipped' - with respect to the thickened aperture of the shell in some species. Most 20th-century authors did not recognize Pachychilidae as an independent family, but affiliated species under different groups, such as Thiaridae and Pleuroceridae. However, recent revisions based on molecular and morphological evidence have proven their independent and distinct status from the former. This family has no subfamilies (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005).

Genera

Genera within the family Pachychilidae include:

Cladogram

A cladogram based on sequences of mitochondrial 16S ribosomal RNA sequences showing phylogenic relations of Pachychilidae: