On the Cretaceous origin of the Order Syracosphaerales and the genusSyracosphaera

Abstract

New scanning electron microscope observations of unadulterated calcareous nannofossil assemblages on lamina surfaces of Cretaceous Tanzania Drilling Project sediments reveal high diversity in the lagerstatte , but also our discovery of several new Cretaceous taxa provides evidence for greatly extended fossil lineages of extant orders, with implications for both deep-time biodiversity divergence and survival through the end-Cretaceous mass extinction. Our findings include: new species that are the first-recorded Mesozoic representatives of the extant Syracosphaeraceae and Papposphaeraceae; potentially previously unrecorded diversity in the Mesozoic Calciosoleniaceae, another extant order, represented by extant species that have been described already; and new species and unusually high abundances of the Mesozoic Stephanolithiaceae. We also highlight the extended range of an incertae sedis Cenozoic genus, Ellipsolithus , into at least the Turonian. Here, we describe seven new miniscule to very small Cretaceous species: Syracosphaera antiqua , S. repagula , Pocillithus macleodii , P. crucifer , Stradnerlithus wendleri , S .? haynesiae and Tortolithus foramen .