uniplicate
/ˈjuːnɪplɪkət/ /ˌjuːˈnɪplɪkət/Chiefly Palaeontology
adjective
Of (part of) the shell of a brachiopod or mollusc: that has a single fold. Of a brachiopod or mollusc: having such a shell.
Origin
Early 19th century; earliest use found in Abraham Rees (1743–1825), Presbyterian minister and encyclopaedist. From uni- + plicate, after multiplicate.