DEGEO - Departamento de Geologia

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8

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20202

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Autor: search.filters.author.Schneider, SimonTem arquivos: Sim

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    Cratonaia novaolindensis gen. et sp. nov. (Unionida, Silesunionoidea) from the Aptian of Brazil (Araripe Basin), and its implications for the early evolution of freshwater mussels.
    (2020) Silva, Victor Ribeiro da; Varejão, Filipe Giovanini; Matos, Suzana Aparecida; Fürsich, Franz Theodor; Skawina, Aleksandra; Schneider, Simon; Warren, Lucas Veríssimo; Assine, Mario Luis; Simões, Marcello Guimaraes
    The fossil-rich carbonate deposits of the Aptian Crato Formation, Araripe Basin (Brazil) are one of the main Cretaceous Konservat-Lagerstatten of Gondwana, and have come to fame globally. However, in- € formation on fossils from deposits other than the famous laminites of the basal part of the unit is scarce. Herein, we describe the first bivalves of the suborder Silesunionidina Skawina and Dzik, 2011 in the order Unionida Gray, 1854 from South America. The specimens were collected from a 0.3e1-m-thick grey to yellow mudstone interval located 0.3 m above the laminated limestones of the lower part of the Crato Formation at Nova Olinda, State of Ceara. They comprise exquisite composite, internal and external -moulds, preserving key anatomical characters. Based on the analysis of muscle scars, hinge and orna- mentation, these bivalves are here assigned to a new genus and species, Cratonaia novaolindensis gen. et sp. nov. The presence of a series of small pedal elevator scars linearly arranged on the external wall of the umbonal cavity indicates that this is a member of the suborder Silesunionidina. The new form is the by far youngest representative of this group. Closely related bivalves were previously reported from Triassic deposits of Australia, Africa, Europe and potentially India. Detailed stratigraphic, sedimentological and taphonomic observations indicate that the new taxon thrived in a freshwater lake. The occurrence of Silesunionoidea in the Lower Cretaceous of South America indicates that the condition of the musculature in Mesozoic freshwater mussels needs to be established to assign them confidently at family level.
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    New freshwater mussels (Bivalvia, Unionida) with potential trigonioidid and hyriid affinities from the Early Cretaceous of Brazil.
    (2020) Silva, Victor Ribeiro da; Varejão, Filipe Giovanini; Matos, Suzana Aparecida; Rodrigues, Mariza Gomes; Fürsich, Franz Theodor; Skawina, Aleksandra; Schneider, Simon; Warren, Lucas Veríssimo; Assine, Mario Luis; Simões, Marcello Guimaraes
    Two new taxa of freshwater mussels (Bivalvia: Unionida) from the Aptian Crato Formation of the Araripe Basin, NE Brazil, are described. The fossil bivalves are confined to 30- to 130-cm-thick bioturbated mudstones overlying the fossil-rich laminated limestones of the Crato Formation Konservat- Lagersta ̈tte. Individuals are often preserved with closed or splayed articulated valves, some of them potentially in life position, forming an autochthonous to parautochthonous assemblage. Monginellopsis bellaradiata nov. gen., nov. sp. shares key characters with the Trigonioidoidea: (i) the anterior pedal retractor muscle scar is clearly separated from the anterior adductor muscle scar; (ii) the shell has fold- like radial ribs on the posterior half; (iii) a right valve anterior tooth has a striated facet. Araripenaia elliptica nov. gen., nov. sp. is the most abundant and widely distributed unionid of the Crato Formation. Its ornament of anterior inverted V-shaped riblets, and central and posterior radial and sub-radial riblets resembles modern and fossil Hyriidae from the Americas, but also Trigonioidoidea from Eurasia. Its dentition of two smooth anterior pseudocardinals and two smooth posterior laterals in each valve provides no further clues for systematic assignment; muscle scars are not preserved. Assignment to the Hyriidae would make Araripenaia the oldest member of this family known from South America. Moreover, this bivalve assemblage of trigonioidoidids, hyriids, and previously reported silesunionoids suggests palaeobiogeographic links to other areas in both Gondwana and Laurasia.