Silvia Gnaedinger

CONIFEROUS WOODS AND WOOD-DECAYING FUNGI FROM THE EL FRENO FORMATION (LOWER JURASSIC), NEUQUEN BASIN, MENDOZA PROVINCE, ARGENTINA

Abstract. Two species of coniferous silicified wood are described from the El Freno Formation (Lower Jurassic) at Cerro La Brea, on the southern margin of the Atuel River, southern Mendoza Province, Argentina. Agathoxylon liguaensis Torres and Philippe (Araucariaceae) and the new species Podocarpoxylon atuelensis sp. nov. (Podocarpaceae) were described based on a detailed description of the secondary xylem. Wood specimens are well preserved, although some sections display variably decaying cell-walls typical of white-rotting by extant fungi. Vegetative and sexual structures in the degraded areas are identifiable as basidiomycetes. This is consistent with fungal saprotrophism and supports the role of fungi in the recycling of the organic matter in Mesozoic terrestrial ecosystems. Considering the available geochronologic and biostratigraphic data and the current lithostratigraphic settings proposed for the unit, the age of the El Freno Formation at the studied locality can be constrained to the Hettangian-Sinemurian.

FIRST RECORD OF CONIFER WOOD FROM THE CAÑADÓN ASFALTO FORMATION (EARLY–MIDDLE JURASSIC), CHUBUT PROVINCE, ARGENTINA

Abstract. A new fossil conifer wood —Brachyoxylon currumilii sp. nov.— is described from the Lower—Middle Jurassic of Chubut Province (Argentina). The specimens were collected at a locality where the Cañadón Asfalto Formation is exposed, in the vicinity of the Cerro Cóndor village. The studied wood is characterized by mixed pitting in radial tracheid walls (predominantly uniseriate), araucarioid cross fields, low uniseriate rays and the absence of resin canals. The use of transmitted light and epifluorescence microscopy together with SEM imaging allowed the identification of additional characters such as the presence of pitting with torus-margo and compression wood. These characters are discussed in terms of their systematic relevance. On these grounds, the systematic affinity of the studied wood is discussed and linked to the extinct conifer family Cheirolepidiaceae, one of the dominant plant groups during the Jurassic and Cretaceous in Patagonia.

FIRST RECORD OF VOLTZIALEAN MALE CONE (LUTANTHUS) AND PODOCARPACEAN FEMALE CONE (RISSIKISTROBUS) FROM THE LATE TRIASSIC OF ARGENTINA, INCLUDING NEW PLANT REMAINS FROM THE PASO FLORES FORMATION

Abstract. New plant remains from the upper section of the Paso Flores Formation, at the Cañadón de Pancho locality, western area of the Collón Curá River, Neuquén Province, Argentina, are herein described and illustrated. These are: Lutanthus ornatus, Rissikistrobus plenus, Rissikistrobus reductus, Rissikia media, Umkomasia sp., Sphenobaiera argentinae, Pseudoctenis spatulata, Taeniopteris crassinervis and Yabeiella brackebuschiana. Additionally, Baiera triassica, in replacement of the homonymous species previously identified in Argentina as Baiera taeniata, Ginkgo taeniata and Sphenobaiera taeniata, is herein described. Furthermore, species previously described for other localities in the Paso Flores Formation are recorded for the first time for the Quemquemtreu area of the Cañadón Pancho locality. These species are: Asterotheca rigbyana, Marattiopsis muensteri, Cladophlebis kurtzii, C. indica, Dictyophyllum (Dictyophyllum) tenuifolium, Goeppertella stipanicicii, Dicroidium incisum, D. odontopteroides, D. lancifolium, Pachydermophyllum praecordillerae, Heidiphyllum elongatum, Baiera furcata, Sphenobaiera robusta, Pseudoctenis carteriana and P. falconeriana. The Voltziales male cone Lutanthus herein described from the Paso Flores Formation represents its second record for the Gondwana realm while the Podocarpaceae female cone Rissikistrobus is hereby reported for the first time from Triassic strata of Argentina and constitutes its third record for Gondwana. Comparisons with the plant diversity recorded from other localities of the Paso Flores Formation throughout the Neuquén Province are analyzed. The Cañadón de Pancho microflora assemblages suggest a Late Triassic (Latest Norian= Rhaetian) age and therefore the fossil flora is the youngest recorded from Argentinian Triassic basins to date.

Coniferous wood of Agathoxylon from the La Matilde Formation, (Middle Jurassic), Santa Cruz, Argentina

Abstract. In this contribution, four species of Agathoxylon are described from the La Matilde Formation, Gran Bajo de San Julián and central and south-western sectors of Santa Cruz Province, Argentina. Agathoxylon agathioides (Kräusel and Jain) n. comb., Agathoxylon santalense (Sah and Jain) n. comb., Agathoxylon termieri (Attims) Gnaedinger and Herbst, and the new species Agathoxylon santacruzense n. sp. are described based on a detailed description of the secondary xylem. In this work, it was possible to construct scatter plots to elucidate the anatomical differences between the fossil species described on quantitative anatomical data. Comparisons are made with other Agathoxylon species from Gondwana. These parameters can be used to discriminate genera and species of wood found in the same formation, as well as to establish differences/similarities between other taxa described in other formations. Some localities contain innumerable “in situ” petrified trees, which allowed us to infer that these taxa formed small forests, or local forests, or small forests within a dense forest, which is a habitat coincident with the extant Araucariaceae.

First record of Annonaceae wood for the Neogene of South America, Amazon Basin, Brazil

The relief of the regions of Manaus and Itacoatiara, Central Amazon, is supported by Neogene siliciclastic rocks, bounded at the base and top by lateritic paleosols and covered by quaternary sedimentary deposits from the Solimoes-Amazon river system. This unit is informally assigned to the Novo Remanso Formation, consists of usually reddish and ferruginized sandstones, conglomerates and pelites, with few identified fossil records, a fact that has hindered its stratigraphic position, and the paleoenvironmental reconstruction of the last phase of the Amazon Basin settling. This study describes, for the first time, the occurrence of fossil wood in outcroppings of the left bank of the Amazon River, where anatomical and morphological data has enabled its characterization to the species level. Thus, the data marks the record of the Annonaceae in South America, as well as the depositional processes related to incorporation of organic material in the sandy layer and the fossilization processes that allowed its preservation. In an unprecedented way, this study has described Duguetiaxylon amazonicum nov. gen and sp. and provided information on the anatomical and systematic character, as well as data on plant-insect interaction, and a better understanding of the family.

A New Name for Baiera taeniata Geinitz, Ginkgo taeniata (Geinitz) Frenguelli, and Sphenobaiera taeniata (Geinitz) Morel, Ganuza and Zúñiga

1Centro de Ecología Aplicada del Litoral, Área de Paleontología, Consejo Nacional de Investigaciones Científicas y Técnicas, (CECOAL-CCT CONICET Nordeste-UNNE), Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste (FaCENA-UNNE), Casilla de Correo 291, W3410CDB Corrientes, Argentina. 2Laboratorio de Paleopalinología, Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA-CCT CONICET Mendoza), Centro Científico Tecnológico, Consejo Nacional de Investigaciones Científica y Técnicas, Casilla de Correo 330, M5502IRA Mendoza, Argentina. SILVIA C. GNAEDINGER1 ANA MARIA ZAVATTIERI2