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      A minute ostracod (Crustacea: Cytheromatidae) from the Miocene Solimões Formation (western Amazonia, Brazil): evidence for marine incursions?

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          Abstract

          A huge wetland (the ‘Pebas system’) covered western Amazonia during the Miocene, hosting a highly diverse and endemic aquatic fauna. One of the most contentious issues concerns the existence, potential pathways and effects of marine incursions on this ecosystem. Palaeontological evidences (body fossils) are rare. The finding of a new, presumably marine ostracod species ( Pellucistoma curupira sp. nov.) in the upper middle Miocene Solimões Formation initiated a taxonomic, ecological and biogeographical review of the genus Pellucistoma. We demonstrate that this marine (sublittoral, euhaline), subtropical–tropical taxon is biogeographically confined to the Americas. The biogeographical distribution of Pellucistoma largely depends on geographical, thermal and osmotic barriers (e.g. land bridges, deep and/or cold waters, sea currents, salinity). We assume an Oligocene/early Miocene, Caribbean origin for Pellucistoma and outline the dispersal of hitherto known species up to the Holocene. Pellucistoma curupira sp. nov. is dwarfed in comparison to all other species of this genus and extremely thin-shelled. This is probably related to poorly oxygenated waters and, in particular, to strongly reduced salinity. The associated ostracod fauna (dominated by the eurypotent Cyprideis and a few, also stunted ostracods of possibly marine ancestry) supports this claim. Geochemical analyses (δ 18O, δ 13C) on co-occurring ostracod valves ( Cyprideis spp.) yielded very light values, indicative of a freshwater setting. These observations point to a successful adaptation of P. curupira sp. nov. to freshwater conditions and therefore do not signify the presence of marine water. Pellucistoma curupira sp. nov. shows closest affinities to Caribbean species. We hypothesize that Pellucistoma reached northern South America (Llanos Basin) during marine incursions in the early Miocene. While larger animals of marine origin (e.g. fishes, dolphins, manatees) migrated actively into the Pebas wetland via fluvial connections, small biota (e.g. P. curupira sp. nov.) were phoretically freighted and developed freshwater tolerance over long timescales.

          http://zoobank.org/urn:lsid:zoobank.org:pub:886C6476-393D-4323-8C0E-06BB8BD02FD9

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          Marine incursions and the influence of Andean tectonics on the Miocene depositional history of northwestern Amazonia: results of a palynostratigraphic study

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            An environmental reconstruction of the palaeo-Amazon River system (Middle–Late Miocene, NW Amazonia)

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              Late Miocene onset of the Amazon River and the Amazon deep-sea fan: Evidence from the Foz do Amazonas Basin

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                Author and article information

                Journal
                J Syst Palaeontol
                J Syst Palaeontol
                TJSP
                tjsp20
                Journal of Systematic Palaeontology
                Taylor & Francis
                1477-2019
                1478-0941
                2 July 2016
                2 October 2015
                : 14
                : 7
                : 581-602
                Affiliations
                [ a ]Department for Geology and Palaeontology, Universalmuseum Joanneum , Weinzöttlstrasse 16, 8045 Graz, Austria
                [ b ]Coordenação de Ciências da Terra e Ecologia, Museu Paraense Emílio Goeldi, Avenida Perimetral, 1901 , Terra Firme, Belém-PA 66077-830, Brazil
                [ c ]Institute of Earth Sciences, University of Graz, NAWI Graz , Heinrichstrasse 26, 8010 Graz, Austria
                Author notes
                [* ]Corresponding author. Email: martin.gross@ 123456museum-joanneum.at
                Article
                1078850
                10.1080/14772019.2015.1078850
                4936381
                27453692
                5c02ba18-c067-404a-bef8-8eaac438b27c
                © 2015 The Author(s). Published by Taylor & Francis.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 13 April 2015
                : 15 June 2015
                Page count
                Figures: 6, Tables: 0, References: 189, Pages: 22
                Categories
                Article
                Original Articles

                pellucistoma,biogeography,palaeogeography,palaeoecology,dispersal mechanisms,freshwater adaptation

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