domenica 1 settembre 2013

A new Oligocene-Miocene calcareous nannofossil species: Pontosphaera wallacei

Persico D. and Villa G.


Derivatio nominis: in honour of Alfred Russel Wallace, a British naturalist, in the centenary of his death (8 January 1823 – 7 November 1913). He is best known for independently conceiving the theory of evolution through natural selection, which prompted Charles R. Darwin to publish his own ideas in “On the Origin of Species”.

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A high-resolution study of sediments from DSDP Leg 72 Site 516 provided the opportunity to reconstruct a detailed biostratigraphy for the late Oligocene - early Miocene time interval. The detailed taxonomic investigation of calcareous nannofossils, performed by a quantitative analysis, highlighted the presence of a species of Pontosphaera that does not show the morphologic features of any recognized species of this genus. This species, which was previously classified as Pontosphaera sp., is here described as Pontosphaera wallacei nov. sp.



Description: the central area is closed and composed by 19-20 flattened crystals, with variable shape, arranged radially to form a central longitudinal slit. Typically V-units form the narrow imbricate outer rim, and R-units form the inner rim and the central area (Young and Bown, 1991).

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