New species of the genus Trochoguembelitria from the lowermost Danian of Tunisia - biostratigraphic and evolutionary implications in planktonic foraminifera

摘要

Two lineages of primitive trochospiral species emerged in the earliest Danian after the Cretaceous/Paleogene (K/Pg) mass extinction event, one exhibiting a smooth wall texture with mural pores and the other, a pustulate to rugose wall texture consisting of blunt pustules and small rugosities, imperforate or with decentred pores, and scattered pore-mounds. This evolutionary scenario is based on Tunisian sections, particularly the El Kef section, whose continuity, completeness, abundance and excellent preservation of the foraminifera make it the best locality worldwide for analyzing the taxonomy and evolution of the early Danian planktonic foraminifera. The first lineage appeared about 5 kyr after the K/Pg boundary catastrophic mass extinction and is attributed to the parvularugoglobigerinids (Parvularugoglobigerina and Palaeoglobigerina). The second lineage appeared approximately 35 kyr after the K/Pg boundary event and is assigned to Trochoguembelitria ARENILLAS, ARZ & NANEZ, 2012. Morphological and morphostatistical analyses of Trochoguembelitria discriminate at least four species, two of them usually assigned to parvularugoglobigerinids: T alabamensis (LIU & OLSSON, 1992) and T. extensa (BLOW,1979); and two new species: T liuae sp. nov. and T. olssoni sp. nov.