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The Bivalvia — Proceedings of a Memorial Symposium in Honour of Sir Charles Maurice Yonge, Edinburgh, 1986. (Edited by Brian Morton). Hong Kong University Press, Hong Kong, 1990. AN INTRODUCTION T O TH E RAZO R SHELL S (BIVALVIA: SOLENACEA ) R. von Cosel Museum National d'Histoire Naturelle, 55, rue de Buffon, 75005 Paris, France ABSTRACT The Solenacea (Solenidae with Solenand Solenaand Pharidae with Ensis,Phaxas, Cultellus, Pharus, Siliqua, Sinonovacula, Pharella and Orbicularia) are a commercially important soft bottom infaunal marine bivalve group. It is proposed that Pharus, hitherto grouped in the Tellinacea, be placed in the Solenacea within the Cultellidae (which has to change its name to Pharidae as a consequence), based on conchological and anatomical characters such as the similar general arrangement of the hinge teeth, lack of a cruciform muscle , foot shape and the separate style sac and midgut. Conchological characters such as the hinge teeth arrangement and the scars of the accessory pedal musculature suggest moving Orbicularia from the Tellinacea (Psammobiidae) to the Solenacea. The Solenacea are highly specialized and successful in their biotopes, mostly fine sand, silt or mud, rarely pure mud. Solenidae are known since the early Eocene, the Pharidae since the upper Cretaceous; both families hav e achieved their greatest specie s diversity i n the Recent fauna . Abou t 60-6 5 livin g specie s o f Solenida e ar e presently known . The y ar e predominantly tropical and subtropical with the distribution centre in the Indo-West Pacific and only a few species in temperate zones. The number of Recent Pharidae is estimated at 50-57 species . Ensis i s mostly war m to cold-temperate, with thre e tropical species , the distribution centr e i s «NW-Europe. Pharus i s exclusivel y Easter n Atlanti c wit h severa l species in tropical West Africa. Phaxas and Cultellus are mainly tropical with few temperate species, and Siliqua ranges from cold water to the tropics. There are no Ensis in the IndoPacific , n o Siliqua i n th e Easter n Atlantic , n o Phaxas an d Cultellus i n th e Wester n Hemisphere and no Solenacea in New Zealand. Solenacea are mostly continental, few Solen and Phaxas being recorded from oceanic islands. INTRODUCTION . The Solenacea ar e a soft botto m infaunal marin e bivalve group with a more or less 284 R. VO N COSE L narrow and long shell, gaping at both ends. In comparison to other infaunal bivalve families such as the Cardiidae , Psammobiidae, Tellinidae, Veneridae, the Solenacea are not species rich, but commercially quite important. The peculiar shell form and the mode of life of this group hav e attracte d th e attentio n o f naturalist s an d malacologist s resultin g i n a n earl y literature: Deshayes (1839), Forbes and Hanley (1848), Jeffreys (1865) , P. Fischer (1887). In many of these Aristotle is referred to as the first who noticed the life habits of the razor shells and who called them 'solen'. This is cited in detail, e.g., in Forbes and Hanley (1848: 240) and Jeffreys (1865) . In the modern literature (see below) emphasis has been put on anatomy, physiology and ecology. For C M . Yonge, the Solenidae was 'one of the most highly specialized families' o f bivalves (Yonge, 1952 ) and one of his favourite groups to which he often referred when dealing with bivalve evolution. SYSTEMATICS The genus Solen was established by Linne (1758), but it also included species in other families, e.g., Cultellidae, Solecurtidae, Laternulidae, ?Cardiidae and Glaucomyidae (Linne, 1767). The Solenida e an d th e Solenace a wer e erected b y Lamarck (1809 ) an d include d solecurtids. Cultellus an d Ensis wer e establishe d b y Schumache r (1817) . Th e tellini d bivalves of the Solecurtidae were included within the Solenacea by Deshayes (1839), Adams and Adams (1858), Chenu (1862) , Conrad (1867), P. Fischer (1887), Clessin (1888) and Ghosh (1920), though the latter separated them in the Solecurtinae. Conversely, Forbes and Hanley (1848 ) grouped them in the separate family Solecurtidae . Thiele (1935) dropped Solecurtus an d Tagelus fro m th e Solenace a an d unite d the m wit h Psammobia i n th e Psammobiidae. Davies (1935) proposed the Cultellidae, but this separation into two families entered the general systematic bibliography only partly with Vokes (1967) and completely with Keen in Moore (1969), followed by Habe (1977), Vokes (1980) and Boss (1982). Owen (1959...

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