Australian progymnosperms: new discoveries from the Devonian of New South Wales

Abstract : In Australia there is only a poor fossil plant record for the time interval separating the famous Baragwanathia flora of Ludlow-Pragian age and the Late Devonian Leptophloeum flora, both being dominated by lycophyte remains. Much of the Devonian sequence is exposed in the Eden-Bermagui area on the NSW south coast (Young 2007), with the lowermost Bunga beds (freshwater deposits) yielding a fish fauna and abundant plant remains of Middle or Late Devonian age, possibly Emsian or Eifelian based on the fish (Young et al. 2010). Plant fossils include aneurophytalean progymnosperms and lycopsids. The former are represented by 3-7 mm wide fragments of axes bearing opposite decussate branches. Terminal appendages may exceed 10 mm in length, are dichotomous, and divide up to four times. One 3.5 mm wide fertile branch bears two large fertile organs arranged oppositely. The fertile organs are 30 mm long and recurved adaxially. Their distalmost divisions are arranged pinnately and bear masses of sporangia. Individual sporangia are elongate and up to 2 mm long. These fossils are compared to Tetraxylopteris schmidtii, a species widely documented in late Eifelian to Frasnian deposits of Laurussia, and to T. reposana from Venezuela localities of possible early Frasnian age. Two types of lycopsid bark are recorded from the Bunga beds (White 1986), one assigned to Lepidosigillaria linearis, an arborescent species first described in the Frasnian of New York State. The aneurophytaleans of Tetraxylopteris-type from Riverside Quarry, a well-known Givetian locality of New York, formed the understorey of the earliest forests, under a cover of cladoxylopsid trees (Stein et al. 2012). The association of Tetraxylopteris-like plants with arborescent Lepidosigillaria reported here suggests that the former may have played a similar role in the early lycopsid forests of East Gondwana
Type de document :
Communication dans un congrès
9th European Palaeobotany and Palynology Conference, Aug 2014, Padova, Italy. 2014
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Soumis le : jeudi 16 octobre 2014 - 15:06:23
Dernière modification le : vendredi 19 octobre 2018 - 15:26:10

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  • HAL Id : hal-01075058, version 1

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Anne-Laure Decombeix, Brigitte Meyer-Berthaud, Philippe Gerrienne, Robert Dunstone, Gavin C. Young, et al.. Australian progymnosperms: new discoveries from the Devonian of New South Wales. 9th European Palaeobotany and Palynology Conference, Aug 2014, Padova, Italy. 2014. 〈hal-01075058〉

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