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Re-Evaluation of the Genus Rubidgea in the Lower Permian of the Paraná Basin, Brazil, and Its Biostratigraphic Consequence

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Re-Evaluation of the Genus Rubidgea in the Lower Permian of the Paraná Basin, Brazil, and Its Biostratigraphic Consequence Versão online: http://www.lneg.pt/iedt/unidades/16/paginas/26/30/185 Comunicações Geológicas (2014) 101, Especial I, 455-457 IX CNG/2º CoGePLiP, Porto 2014 ISSN: 0873-948X; e-ISSN: 1647-581X Re-evaluation of the genus Rubidgea in the Lower Permian of the Paraná Basin, Brazil, and its biostratigraphic consequence Reavaliação do género Rubidgea, no Pérmico Inferior da Bacia do Paraná, Brasil, e suas consequências bioestratigráficas R. Iannuzzi1*, G. P. Tybusch1 Artigo Curto Short Article © 2014 LNEG – Laboratório Nacional de Geologia e Energia IP Abstract: The plant megafossil specimens revised in this study came *Corresponding author / Autor correspondente: [email protected] from the outcrops located in the São Paulo and Rio Grande do Sul states and positioned stratigraphically on top of the Itararé Group 1. Introduction and/or base of the Rio Bonito (= Tietê) Formation, Lower Permian of the Paraná Basin. The study material comprises leaves fragments The record of the genus Rubidgea in Brazil was first preserved as impressions, previously included in the morphogenus mentioned by Cazzulo-Klepzig et al. (1980) for the Itararé Rubidgea because of their supposed gangamopterid venation pattern, Group of the Rio Grande do Sul state, and it is represented lacking anastomoses. However, re-evaluation of this material showed by a specimen classified as Rubidgea sp. Later, Rubidgea that these leaves bear at some degree, rare anastomoses along the lamina. Based on this observation, we proposed that these leaves obovata Maithy (1965) and Rubidgea lanceolatus Maithy should be transferred to the morphogenus Gangamopteris, which (1965) were illustrated and reported for the outcrops displays this type of venation. Consequently, the reclassification of Acampamento Velho, Morro do Papaléo, Fazenda Goulart these glossopterids into species of Gangamopteris made possible a and Faxinal, corresponding to the top of the Itararé Group more direct correlation between the Early Permian strata in the north in Rio Grande do Sul state (Cazzulo-Klepzig et al., 1980; and south portions of the Paraná Basin based on megafloristic Guerra-Sommer et al., 1980; Guerra-Sommer & Cazzulo- comparison. Klepzig, 1981). However, the specimens were not formally Keywords: Rubidgea, Gangamopteris, Paraná Basin, Lower described by those authors. Permian, Brazil. Millan & Dolianiti (1982) described and identified a Resumo: Os espécimes de plantas fósseis revisados neste estudo total of four species of the genus Rubidgea from Sítio vieram de afloramentos localizados nos estados de São Paulo e Rio Itapema, in the Cerquilho municipality, São Paulo state: R. Grande do Sul, posicionados estratigraficamente na parte superior do obovata, R. lanceolata, R. lanceolata var. truncata and R. Grupo Itararé e/ou na base da Formação Rio Bonito (= Tietê), itapemensis. The two latter taxa represented new species Pérmico Inferior da Bacia do Paraná. O material de estudo é composto por fragmentos de folhas preservados como impressões, erected by these authors at that time. The deposit is related previamente incluídos na morfogénero Rubidgea por causa de seu to the top of the Itararé Group (or Tietê Formation) in São suposto padrão de venação gangamopteridea onde faltam Paulo state. In the same work, the authors also provided an anastomoses. No entanto, a reavaliação deste material mostrou que emended diagnosis for the genus Rubidgea, originally estas folhas suportam, em algum grau, raras anastomoses ao longo da erected by Tate (1867), adding characters regarding the lâmina. Com base nesta observação, foi proposto que estas folhas leaf morphology, such as the shapes of the lamina, apex devem ser transferidas para o morfogénero Gangamopteris, que exibe este tipo de venação. Consequentemente, a reclassificação and base and the type of margin. destes glossopterídeos em espécies de Gangamopteris possibilitou Rohn et al. (2000) reported the occurrence of Rubidgea uma correlação mais direta entre os estratos do Eopermiano nas sp. for a tafoflora comprising Gangamopteris sp., porções norte e sul da Bacia do Paraná com base na comparação Noeggerathiopsis?, Samaropsis sp., sphenophytes and some megaflorística. fructifications, recovered from the Itararé Group strata Palavras-chave: Rubidgea, Gangamopteris, Bacia do Paraná, outcropping along the margins of the river Capivari, in Tietê Pérmico Inferior, Brasil. municipality, São Paulo state, considered Late Carboniferous to Early Permian in age. However, the 1 authors did not describe the specimens, but only figured Instituto de Geociências, Universidade Federal Rio Grande do Sul. Av. Bento Gonçalves, 9500, CEP 91.540-000, Porto Alegre, RS, Brasil. E-mail: them with photos and mentioned the Rubidgea and [email protected]; [email protected], “Bolsistas do Gangamopteris specimens. CNPq – Brasil. 456 R. Iannuzzi, G. P. Tybusch / Comunicações Geológicas (2014) 101, Especial I, 455-457 Based on the classification criteria usually considered in specimens described and identified as Rubidgea by Millan & the distinction of leaf morphogenera, Tybusch & Iannuzzi Dolianiti (1982) exhibited anastomoses along the blade, (2008) have recently showed that forms previously despite being a rare feature. Because this characteristic is not attributed to the genus Rubidgea are absent from the Lower found in the original diagnosis of the genus Rubidgea, but in Permian deposits on top of the Itararé Group and in the Rio that of Gangamopteris, all the material studied by Millan & Bonito Formation, Rio Grande do Sul state. The authors Dolianiti (1982) was transferred to the latter. Thus, we analysed and revised about 70 specimens from localities of believe that the genus Rubidgea is absent in the Permian the two deposits and concluded that the specimens deposits of the São Paulo state, as well as in those from Rio previously assigned to Rubidgea should be in fact, classified Grande do Sul. The only record left of the genus in the as Gangamopteris, since they display the morphografic Paraná Basin is that of Rohn et al. (2000) for the characters that correspond to those found in the original Carboniferous-Permian interval strata of Tietê, São Paulo diagnosis of Gangamopteris, such as: (i) lack of a visible state. The material comprises two illustrated forms classified median venation, and mainly, (ii) though rare, the presence as Rubidgea sp. However, when the photos published by the of anastomoses along the leaf lamina. authors (Rohn et al., op. cit. p. 60, pl. I, Figs. 2 and 4) were Considering that Rubidgea is a very rare taxon in analysed, we noticed that these specimens were poorly Gondwana – there is only one occurrence in South Africa preserved, resulting in an unclear venation pattern, what and another in India (Tate, 1867; Maithy, 1965) – the makes difficult or even impossible to observe anastomoses, present contribution aimed to extend the taxonomic re- especially if they are rare. This can lead to misinterpretations evaluation to all forms previously described and included in of the venation pattern of the specimens, like those this genus and that were recovered from the northern parts mentioned in Kovács-Endrödy (1977) for South African of the Paraná Basin (e.g. São Paulo state), specially from the forms. Because of this, we preferred to consider the outcrop Cerquilho Velho. This paper represents the occurrence of Rubidgea as dubious for the material published continuation of the revision project of the specimens in Rohn et al. (2000). For instance, there is strong evidence classified as Rubidgea, found in the deposits of the south suggesting that the morphogenus Rubidgea is not present in portion of the basin (e.g. Rio Grande do Sul state) the deposits of the Paraná Basin, since all previous previously published by the authors (Tybusch & Iannuzzi, occurrences based on well preserved specimens were refuted. 2008). In addition, this work is part of the PhD thesis of the Some authors (Arber, 1905; Seward, 1907; Kovács- co-author (Tybusch, 2013). Endrödy, 1977) believed that the morphogenus Rubidgea was not valid. Here we speculate that those who erected new 2. Morphogenera Rubidgea and Gangamopteris species/varieties for this genus or pointed its occurrence made it due to misinterpretations (i.e. Tate, 1867; Maithy, The identification of each morphogenus amongst 1965; Cazzulo-Klepzig et al., 1980; Guerra-Sommer et al., glossopterid leaves is based mainly on characteristics of 1980; Guerra-Sommer & Cazzulo-Klepzig, 1981; Millan & the venation pattern (presence/absence of median venation Dolianiti, 1982). But, it will be still necessary a careful and type of secondary venation), while the shape and size revision of the Indian specimens described by Maithy (1965), of the leaves are features that have been used only to in order to conclude if the genus is valid or not. distinct the morphospecies when they have a very similar Anyway, the re-evaluation and consequent assignment of venation pattern. the material from São Paulo to Gangamopteris spp. made Considering this, the specimens revised in the present possible a more direct correlation among the Early Permian study were re-classified at generic level, based mainly on deposits of the north and south portions of the Paraná Basin the characteristics of the venation pattern. Thus, based on megafloristic comparisons. It would like to Gangamopteris is considered a type of leaf recognized by highlight that the Gangamopteris species found in Cerquilho the absence of median venation, but sometimes
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