dinoflagellate

borrowed from New Latin Dinoflagellatum, presumed singular of Dinoflagellata, order name, from dino- (in Dinophysis, Peridinium and the genus names of other protists having a second flagellum in a transverse groove; borrowed from Greek dīn-, in dīneîn "to whirl, spin about," dī́nē "whirlpool, eddy," dînos "whirling, rotation, eddy," probably originally a verbal base, of obscure origin) + Flagellata, former order name, from neuter plural of flagellātum flagellate entry 2

Note: The name was introduced in the 1880's by the German zoologist Otto Bütschli (1848-1920); in his paper "Einige Bemerkungen über gewisse Organisationsverhältnisse der sog. Cilioflagellaten und der Noctiluca," Morphologisches Jahrbuch, 10. Band (1885), pp. 529-77, Bütschli suggests the name as an alternative to Cilioflagellata, on the grounds that the girdle of cilia thought to characterize these protists is actually a flagellum fit inside a transverse groove: "In any case the need arises to exchange the name Cilioflagellata for another, as it rests on a really incorrect conception of its structure … I can also not recommend Stein's designation as the arthrodelous ['clearly jointed'] Flagellata, and I would hence like to propose the name Dinoflagellata, which at once calls to mind the earlier name Cilioflagellata in a certain respect, and then as well expresses the most characteristic peculiarities of the typical forms, that is, the formation of a transverse groove storing a flagellum." ("Jedenfalls wird sich aber die Nothwendigkeit ergeben, die Bezeichnung Cilioflagellaten mit einer anderen zu vertauschen, da sie auf einer tathsächlich unrichtigen Auffassung des Baues beruht … Mit Stein die Cilioflagellaten als arthrodele Flagellaten zu bezeichnen, halte ich auch nicht für empfehlenswerth und möchte daher vorschlagen, die Bezeichnung Dinoflagellata zu gebrauchen, welche einmal in gewisser Hinsicht an den früheren Namen Cilioflagellaten erinnert und dann die für die typischen Formen charakteristischste Eigenthümlichkeit, nämlich die Ausbildung der Querfurche mit der eingelagerten Geissel zum Ausdruck bringt.") Bütschli does not state explicitly why he chose dino-, though it most likely simply reflects the use of the form in genus names of protists possessing the second flagellum. The zoologist E. Ray Lankester, in the article on Protozoa for the ninth edition of the Encyclopaedia Britannica (1885), suggests in a discussion of Dinoflagellata that the allusion is to "Gr. dinos, the round area where oxen tread out on a threshing floor"—though this seems somewhat speculative and the relevance of dínos to a particular feature of the organism is not evident.