A new genus, Popenoeum, is proposed for a clade of Upper Cretaceous through lower Eocene pseudolivine gastropods found in North and South America, West Greenland, western Europe, and southern India. Popenoeum n. gen. is characterized by tabulate whorls with a prominent subsutural canal, collabral costae that terminate as tubercles on the body whorl shoulder, and closely spaced fine to strong spiral cords.
The type species, Popenoeum maritimus n. sp., is from the lower Paleocene (Danian) portion of the San Francisquito Formation, southern California, and from the upper Paleocene (Thanetian) Sepultura Formation, Baja California. Popenoeum maritimus bajaensis n. subsp. is also present in the Sepultura Formation.
Other species and subspecies in the clade include Popenoeum sp. (Toulmin) and P. scalina Heilprin from Alabama; P. mutabilis mutabilis (Woods) and P. mutabilis woodsi (Olsson) from northwestern Peru; P. aff. P. maritimus from West Greenland; P. brevis (Doncieux) and P. prima (Defiance) from France; P. chavani (Glibert), P. robusta (Briart and Cornet) and P. briarti (Vincent) from Belgium; and P. subcostata (Stoliczka) from southern India. The earliest species is P. subcostata, and it is the only Cretaceous species. The youngest form is P. mutabilis woodsi, and it is the only Eocene species. The new genus reached its peak during the Paleocene.