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1 February 2013 New “Flower” and Leaves of Bennettitales from Southern Brazil and their Implication in the Age of the Lower Mesozoic Deposits
Ronaldo Barboni, Tânia Lindner Dutra
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Abstract

The record of Bennettitales from west-central Argentina and southern Brazil in South America is among the oldest known. In contrast to the better known near-coastal assemblages from the Northern Hemisphere, these Gondwanic elements are restricted to continental areas and isolated rift basins, similar to those in South Africa. Williamsonia potyporanae sp. nov. is preserved by impressions that expose distinct longitudinal sections of the ovulate structure, allowing the reconstruction of its tridimensional aspect, and is accompanied by probable Pterophyllum leaves. It consists of an ovate-shaped flower covered by two layers of delicate and connected ribbon-shaped and hairy bracts, and an obconic receptacle supporting a great number of megasporophylls, with uniformly aligned and apical fusiform ovules or seeds. The bennettite remains are part of an autochtonous-parautochtonous floral assemblage dominated by conifers and restricted to a thin mudstone interval in a mainly fluvial deposition comprisig the Caturrita Formation. The mud interval suggests a shallow lake supplied by periodic, intense rainfall that affected the vegetation growing along the river banks and/or on a floodplain deposits. An initially proposed Norian age, based on diversified vertebrate remains found in lower levels (Ictidosaur or Mammaliamorpha Cenozone), was recently extended to the Rhaetian. The advanced morphology of ovulate structure described here suggest an even younger Jurassic age, supported by comparisons with other fossil assemblages, mainly those from Argentine basins.

Ronaldo Barboni and Tânia Lindner Dutra "New “Flower” and Leaves of Bennettitales from Southern Brazil and their Implication in the Age of the Lower Mesozoic Deposits," Ameghiniana 50(1), 14-32, (1 February 2013). https://doi.org/10.5710/AMGH.28.11.2012.444
Received: 7 December 2010; Accepted: 1 November 2012; Published: 1 February 2013
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