The aquatic palynomorph genus Cobricosphaeridium Harland and Sarjeant, 1970 was described from Holocene deposits of Australia. Restudy of the type material shows that these palynomorphs may represent the eggs of crustaceans, and that earlier attributions to the division Dinoflagellata are unsustainable. The genus Aquadulcum Harland and Sarjeant, 1970, also first described as a dinoflagellate from the Holocene of Australia, is treated as a synonym of Cobricosphaeridium, and the following new combinations are proposed: C. awendae, C. myalupense, C. pikeae, C. serpens, C. yanchepense, C.? ovatum, and C.? vermiculatum. Previous records of the genus are restricted to the Holocene and indicate a freshwater affinity.
Cobricosphaeridium has now been found in Holocene subsurface brackish deposits of Laguna Hinojales in eastern Argentina. This is the first record of this genus from South America and unequivocally extends its ecological range into a brackish environment. Several species are represented, including Cobricosphaeridium hinojalensis new species; and their potential as paleoenvironmental indicators is evaluated.