Lower Carboniferous (Upper Viséan and Pendleian) rocks from the Guadiato Area, in the southwestern part of Spain, comprise mixed carbonate-siliciclastic platform facies, with siliciclastics predominant. The calcareous intervals contain a highly diversified foraminiferal fauna, composed mainly of endothyroids, although some primitive fusulinids are also present.

Fourteen families, 9 subfamilies, 67 genera, and 134 species or species groups of foraminifera have been identified. These allow the identification of zones 14 to 18 of Mamet’s classification. Within this zonal framework the appearance, disappearance, and maximum abundance of selected taxa in the Guadiato Area are described and discussed. The first appearance of foraminiferal species and genera in the Guadiato Area is compared to that in other European (Montagne Noire, northern France and Belgium; Britain; and Ireland) and North African (Algéria and Morocco) basins. It shows that some foraminifera occurred earlier in Spain whereas other taxa occurred later than in these regions. These early or late appearances of taxa are grouped in two trends, which are probably related to tectonic movements coeval with sedimentation in the Guadiato Area. Moreover, cluster analysis comparing the foraminifera of the twelve neighboring Carboniferous basins or regions establishes the paleobiogeographical relationship between the Guadiato Area and these other regions.