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

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 * ...

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 ...

mollusk 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 e ...

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 and ...

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

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). It follows the Neogene Period and spans from 2.58 million years ...

(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
/ref> Mactridae - Lutraria oblonga-001

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 bivalve mollusc in the family Mactridae. Its common names include the otter shell and the common otter shell. It occurs in coastal regions of the north east Atlantic Ocean where it lives burie ...

'' (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