''Lutraria'' is a genus of medium-sized marine

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

s or clams, commonly known as otter shells.

Characteristics

Members of this genus have large, elongated oval shells with two equal sized

valves A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings, ...

. The anterior end is somewhat sharply curved but the posterior end is more rounded. The valves gape slightly at both ends, more so at the posterior end. The shell is fairly thick and is sculptured with fine concentric lines corresponding to periods of growth. The basic colour is white and the

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods an ...

is brown, but the latter is usually abraded. The interior surface of the valves is glossy white. The beaks are blunt and situated slightly closer to the anterior end. The ligament is small and largely internal. The foot is small and the siphons are long and are housed in a common horny sheath for most of their length.

Biology

These mollusks live buried in sand to a depth of about , usually below low water mark, with their siphons extended to the sea bed. As they grow they burrow deeper but are otherwise relatively sedentary.

Fossil record

Fossils of ''Lutraria'' are found in marine strata from the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

to the

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

(age range: from 33.9 to 0.0 million years ago.). Fossils are known from Europe, South Africa, Japan, New Zealand, Pakistan, Australia, India and Argentina.Paleobiology Database
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Species

*'' Lutraria angustior'' Philippi, 1844 *'' Lutraria budkeri'' Nicklès, 1955 *'' Lutraria capensis'' Reeve, 1854 *'' Lutraria complanata'' (Gmelin, 1791) *'' Lutraria curta'' Reeve, 1854 *'' Lutraria impar'' Reeve, 1854 *'' Lutraria inhacaensis'' Boshoff, 1965 *''

Lutraria lutraria ''Lutraria lutraria'' is a species of large marine Bivalvia, bivalve mollusc in the Family (biology), family Mactridae. Its common names include the otter shell and the common otter shell. It occurs in coastal regions of the north east Atlantic ...

'' (Linnaeus, 1758) *'' Lutraria maxima'' Jonas, 1844 *'' Lutraria oblonga'' (Gmelin, 1791) *'' Lutraria rhynchaena'' Jonas, 1844 *'' Lutraria senegalensis'' Gray, 1837 *'' Lutraria sieboldii'' Reeve, 1854 *'' Lutraria steynlussii'' Huber, 2010 *'' Lutraria turneri'' Jousseaume, 1891

References

{{Taxonbar, from=Q3014365 Mactridae Bivalve genera Taxa named by Jean-Baptiste Lamarck