Aspa marginata is the most readily recognized of all Bursidae, because of its extremely short spire, its very low, wide varices, and its inflated form with an almost smooth surface and no nodules at all. Aspa marginata is extremely well known in the Pliocene to Recent fauna of Europe and West Africa, and nothing even vaguely resembling it ever has been reported from the Americas. It was a surprise, then, to recognize a single half-grown specimen of A marginata in the latest Pliocene-Early Pleistocene fauna of the Moin Fm at Limon, Costa Rica, in the extremely large and diverse collection made by Emily and Harold Vokes. Robinson (1991, 1993) previously recorded A. marginata from the Moin Fm, on the basis of four further specimens collected subsequently by Emily and Harold Vokes.

Cossmann & Peyrot (1924: 313-317), in a long discussion of the characters of fossil ancestors of Aspa marginata in Europe, distinguished a series of species in an evolutionary lineage, and this was discussed again by Landau et al. (2004: 70-71). Material from many localites in the Aquitaine Basin, France, in MNHN (shown to me by Pierre Lozouet) and in Universite Bordeaux-1 in Talence and several private collections in and near Bordeaux (shown to me by Bruno Cahuzac, Alain Clouzaud, and Jean-Francois Lesport), and more from Le Peloua, Saucats, Aquitaine Basin (5 specimens; Burdigalian, Early Miocene) and Termotura strata, Baldissero, Turin Hills, Italy (4 specimens; also Burdigalian), in the collection of Bernard Landau, demonstrate that early forms are consistently distinct from the Recent species. The earliest specimen of Aspa from Europe of which I am aware, from the Early Miocene (Aquitanian; Pierre Lozouet, MNHN, pers. comm., 2003) locality of Gaas, Landes, in the Aquitaine Basin of France, has a surprisingly tall spire and resembles the Indo-West Pacific species Bufonaria margaritula (Deshayes, 1832) (SMF, one specimen). The valid name for this earliest member of the lineage is A. subgranulata (d'Orbigny, 1852). It differs from A. marginata in having a higher spire, coarser sculpture of even granules, a row of nodules at the shoulder persisting onto the last whorl and an obsolescent lower row of nodules, and larger nodules inside the outer lip than in A. marginata. This apparently ancestral species therefore resembles the Indo-West Pacific species of Bufonaria and Bursina much more closely than does A. marginata. Cossmann & Peyrot (1924: 316-317) recognized an intermediate species, A. depressa (Grateloup, 1833), from Middle and Late Miocene rocks of Europe, but Landau et ai (2004: 70) regarded this as varying greatly enough to be considered a synonym of A marginata. Hoernes & Aiungers (1879) material from Lapugy, western Roumania (Badenian, Middle Miocene), examined at NMHV, also seems best included in A. marginata. Dimensions.-TU 1240 = NMB 19008, Moin, Costa Rica: H 21.4, D 15-5 mm; Grund, Vienna Basin, Badenian (Middle Miocene; GNS WM5392): H 48.2, D 31.2 mm; Recent, 40 m, Tenerife, Canary Islands (GNS WM 15205): H 29.2, D 23.3 mm; neotype of Buccinum marginatum, BMNH GG9183a: H 39.6, D 29.0 mm.

Aspa marginata lives today in the Ibero-Moroccan Gulf and down the coast of West Africa from southern Spain to Angola (Gofas et al, 1984: 132), and at the Canary and Cape Verde Islands and at Madeira. A single juvenile specimen was recorded from Seine Bank, Lusitanian seamounts, eastern Atlantic, Seamount 1 cruise, sta. DW78, 33°49'N, 14°23'W, in 235 m, by Gofas & Beu (1993: 102).