THE DISTRIBUTION RANGE OF CALCAREOUS NANNOFOSSIL SPECIES <em>RETICULOFENESTRA PSEUDOUMBILICUS</em> IN THE MIOCENE: AN EXAMPLE OF ECOLOGICAL INFLUENCE ON EVOLUTIONARY DEVELOPMENT

Reticulofenestra pseudoumbilicus is a Neogene calcareous nannofossil species whose highest stratigraphic occurrence (Top) reliable biohorizon in the Pliocene, calibrated at 3.82 Ma. The present record from least Middle Miocene, within an interval around Top Sphenolithus heteromorphus, 13.53 Ma, but its lower distribution range not precisely delineated. study of assemblages sediment cores Integrated Ocean Drilling Program IODP Site U1338 (eastern equatorial Pacific) indicates position for evolutionary emergence (Base) R. pseudoumbilicus, detected Early Miocene with estimated age 16.46 This results new astronomically tuned chronology, which dates deepest sediments to 16.67 Base followed above by temporary disappearance taxon until re-entrance after ~3 Myr. lengthened has been confirmed data other locations low and mid-latitudes Atlantic. lasting ~13 Myr during Neogene, thus characterized variable pattern repeated occurrences disappearances. Comparison benthic foraminifera δ18O δ13C records suggests control global climatic/environmental conditions on these events, particularly temperature variations. recurrent presence stratigraphically different intervals could represent example iterative evolution, expressed as speciation events that are part influenced complex external factors related dynamic climate environmental evolution Miocene.