''Atrina squamifera'', one of several species known as the ''horse mussel'', is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

pen shell. It is a

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Pinnidae The Pinnidae are a taxonomic family of large saltwater clams sometimes known as pen shells. They are marine bivalve molluscs in the order Pteriida. Shell description The shells of bivalves in this family are fragile and have a long and triang ...

. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to South Africa.

Distribution

This species is found from Saldanha Bay to Port Alfred, subtidally to at least 35 m.

Description

This animal has a large fragile shell and can grow up to 390 mm in total length. It has 6–12 ribs running longitudinally down its shell. Each rib bears translucent cup-like projections. The shell does not close at the posterior end and the dark-rimmed white flesh can be seen inside.Day, J.H. 1969. ''Marine Life on South African Shores'' Balkema, Cape Town

Ecology

The horse mussel is a filter feeder. It usually lies buried vertically in mud or sand although it can also be seen on the wooden decks of the trawler wrecks

Orotava Orotava is a genus of tephritid or fruit flies in the family Tephritidae. Species *''Orotava cribrata'' (Jacques-Marie-Frangile Bigot, Bigot, 1891) *''Orotava hamula'' (Johannes C. H. de Meijere, Meijere, 1914) References

Tephritinae ...

and Princess Elizabeth in Smitswinkel Bay. The shell is often heavily overgrown with other invertebrates. The mantle cavity often contains small pea crabs and

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

which eat food filtered from the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

References

{{Taxonbar, from=Q4817561 Endemic fauna of South Africa Pinnidae Bivalves described in 1835