Systematic taxonomy of middle Miocene<i>Sphaeroidinellopsis</i>(planktonic foraminifera)

The taxonomy and phylogeny of the Miocene to Recent genus Sphaeroidinellopsis have been documented in previous studies, but evolution this lineage remains unclear. Some authors debated past, choosing a variety parameters discriminate morphospecies. Here we present new scanning electron microscope analyses specimens from Ocean Drilling Program (ODP) Site 925 (Ceara Rise, western equatorial Atlantic) ODP 959 (Deep Ivorian Basin, eastern Atlantic). Our study reveals transitional individuals disjuncta–Sphaeroidinellopsis kochi, speciation event never described previously. These are characterized by extreme morphological features such as elongated sac-like final chambers, requiring amendments current classification these In paper, an alternative hypothesis is presented discussed, assess observations within evolutionary mosaic Sphaeroidinellopsis.