monothalamous
/ˌmɒnə(ʊ)ˈθaləməs/adjective
1 Entomology. Of a plant gall: having only one chamber. rare.
2 Zoology. Of an animal or protist: having a shell, test, or skeleton with a single chamber.
Origin
Early 19th century; earliest use found in William Kirby (1759–1850), entomologist and naturalist. From mono- + scientific Latin thalamus or its etymon ancient Greek θάλαμος inner chamber + -ous. In sense 2 after French monothalame.