Acroloxidae, commonly known as river limpets, are a taxonomic family of very small, freshwater snail

Freshwater snail

A freshwater snail is one kind of freshwater mollusc, the other kind being freshwater clams and mussels, i.e. freshwater bivalves. Specifically a freshwater snail is a gastropod that lives in a watery non-marine habitat. The majority of freshwater gastropods have a shell, with very few exceptions....

s, aquatic

Aquatic animal

An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...

 pulmonate gastropod limpet-like mollusks with a simple flattened conical shell

Gastropod shell

The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...

 in the clade Hygrophila.

Acroloxidae is the only family within the superfamily Acroloxoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005

Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)

The taxonomy of the Gastropoda as it was revised by Philippe Bouchet and Jean-Pierre Rocroi is currently the most up-to-date overall system for classifying gastropod mollusks...

).

Anatomy

Pulmones are reduced. Sexual cavity and accessory gills

Respiratory system of gastropods

The respiratory system of gastropods varies greatly in form. These variations were once used as a basis for dividing the group into subclasses. The majority of marine gastropods breathe through a single gill, supplied with oxygen by a current of water through the mantle cavity...

 are on the right side.

Genera

Genera within the family Acroloxidae include:

• Acroloxus
  Acroloxus
  Acroloxus is a genus of very small, air-breathing, freshwater snails, or more precisely limpets, aquatic pulmonate gastropods in the family Acroloxidae.-Species:Species in the genus Acroloxus include:* Acroloxus coloradensis J...
  
  Beck, 1838 - type genus
• Baicalancylus Starobogatov, 1967
• Gerstfeldtiancylus Starobogatov, 1989
• Pseudancylastrum Lindholm, 1909