A way-out from the maze of middle Miocene Sphaeroidinellopsis (planktonic foraminifera)

<p>The taxonomy and phylogeny of the Miocene to Recent genus <em>Sphaeroidinellopsis</em> have been documented in previous studies, but the evolution of this lineage remains unclear. Some authors debated this genus in the past, choosing a variety of parameters to discriminate between morphospecies. Here we present new high detail analyses of specimens from Ocean Drilling Program (ODP) Site 925 (Ceara Rise, western equatorial Atlantic) and ODP Site 959 (Deep Ivorian Basin, eastern equatorial Atlantic). We present transitional individuals <em>Sphaeroidinellopsis disjuncta&#8211;Sphaeroidinellopsis kochi</em>, a speciation event never described before. These transitional specimens are characterized by extreme morphological features such as elongated and sac-like final chambers, requiring amendments to the current classification and taxonomy of these morphospecies. An alternative hypothesis is presented to assess these new observations within the evolutionary mosaic of <em>Sphaeroidinellopsis</em>.</p>