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The systematics and phylogenetic relations of the Oligocene species of Heterostegina (Nummulitidae) are poorly known\ud compared to those of Eocene and Miocene species. The new species Heterostegina matteuccii sp. nov., characterized by\ud the combination of an advanced nepionic stage (i.e. very few operculine chambers) and a relatively small proloculus, is\ud here described from the lower Oligocene Caltavuturo Formation of Portella Colla (Madonie Mts, Sicily, Italy). The same\ud species is recorded also in the ‘Calcaire a asteries’ Formation of Illats (Northern Aquitaine, near Bordeaux, France).\ud Biometrically, H. matteuccii sp. nov. does not fit within any known Neo-Tethyan lineage of Heterostegina from the\ud Eocene to the Miocene, and hence is considered to be a member of a distinct phyletic lineage. The advanced nepionic stage\ud of H. matteuccii sp. nov., however, calls for the existence of predecessors. The Priabonian (and possibly also earliest\ud Oligocene) H. ocalana Cushman, 1921 from the American-Caribbean realm is here interpreted as the most probable\ud ancestral form for the H. matteuccii lineage. Thus, an early Oligocene eastward transatlantic migration of this lineage may\ud be inferred. New results of strontium isotope stratigraphy from both sides of the Atlantic Ocean are consistent with this\ud hypothesis

Six late Rupelian populations of Nephrolepidina praemarginata (Douvillé, 1908) have been isolated from a succession of the Caltavuturo Formation (Madonie Mts, Sicily). A total of 25 embryonal parameters were obtained from oriented equatorial sections of megalospheric specimens; 8 indexes were derived from selected parameters and 9 indexes were considered for the neanic apparatus, out of which 2 are introduced here: N05 (number of annuli in a radius of 0.5 mm) and r5 (distance occupied by the first five annuli). The data show marked deviations from the expected trend of traditional biometric measures; this is interpreted as dependent on environmental factors. Previous studies on the succession evidenced an increase in basin depth; this can be inferred also from the biometric analysis of the inner characters of the allochthonous Nephrolepidina tests. Here, we explore the paleobiological potential of parameters linked to embryo size and wall thickness, and discuss how depth-dependent parameters may affect the interpretation of evolutionary trends and biostratigraphy in radial foraminifers.

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