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How many mollusk species have been described by scientists?

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Conchyliologie Tableau de la Classification des Coquilles — mollusk Mollusk shell classification chart, c. 1861.

Scientists have described nearly 100,000 mollusk species, though estimates suggest the total number could be as high as 150,000.1

These invertebrates represent one of the most diverse groups in the animal kingdom, encompassing a wide variety of forms including gastropods (snails and slugs), bivalves (clams and oysters), and cephalopods (squids and octopuses).1