The cycads are an ancient group of seed plants. Fossil stems assigned to the Cycadales are, however, rare and few descriptions of them exist. Here, a new genus of cycad stem, Wintucycas gen. nov., is described on the basis of specimens found in the Allen Formation (Upper Cretaceous) at the Salitral Ojo de Agua locality, Río Negro Province, Argentina. The most remarkable features of Wintucyas are: a columnar stem with persistent leaf bases, absence of cataphylls, a wide pith, medullary vascular bundles, mucilage canals and idioblasts; a polyxylic vascular cylinder; inverted xylem; and manoxylic wood. The new genus was included in a phylogenetic analysis and its relationships with fossil and extant genera of Cycadales were examined. In the resulting phylogenetic hypothesis, Wintucycas is circumscribed to subfamily Encephalartoideae, supporting the existence of a greater diversity of this group in South America during the Cretaceous. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170, 436–458.

No abstract

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.Keywords. Fossil wood. Mesozoic. Patagonia. Brachyoxylon. Cheirolepidiaceae. Resumen. PRIMER REGISTRO DE LEÑO DE CONIFERA DE LA FORMACIÓN CAÑADÓN ASFALTO (JURÁSICO TEMPRA-NO-MEDIO), PROVINCIA DE CHUBUT, ARGENTINA. Se describe una nueva especie de madera fósil de conífera, Brachyoxylon currumilii sp. nov., del Jurásico Inferior a Medio de la provincia de Chubut, Argentina. Los especímenes estudiados fueron coleccionados en una localidad donde aflora la Formación Cañadón Asfalto, en las cercanías de la aldea de Cerro Cóndor. Los troncos, estudiados, se caracterizan por el punteado radial de las traqueidas de tipo mixto, predominantemente uniseriado, campos de cruzamiento de tipo araucarioide, radios uniseriados bajos y ausencia de canales resiníferos. La observación bajo MEB y microscopio con luz transmitida y epifluorescencia permitió además la identificación de caracteres tales como la presencia de torus-margo en las punteaduras y estructuras de leño de compresión. Ambos caracteres son discutidos en relación a su relevancia sistemática. Sobre esta base, se discute la afinidad sistemática de la madera estudiada, la cual posee rasgos que la vincularían con la familia de coníferas extintas Cheirolepidiaceae, uno de los grupos de plantas dominantes durante el Jurásico y Cretácico de Patagonia.Palabras clave. Madera fósil. Mesozoico. Patagonia. Brachyoxylon. Cheirolepidiaceae.

-VOLTZIALES AND PINALES (= CONIFERALES) FROM CORTADERITA FORMATION (MIDDLE TRIASSIC), ARGENTINA, AND THEIR IMPLICATION IN THE RECONSTRUCTION OF TRIASSIC CONIFERS.In this work, fossil wood, leaves, and branches designated to the subclass Pinidae (Voltziales and Pinales) are described from Cortaderita Formation (Middle Triassic). Fossil materials were collected at Cortaderita and La Tinta creeks, at Barreal area from Barreal-Calingasta basin, Pre-Andean region of San Juan, Argentina. Leaves corresponding to three species of Heidiphyllum (order Voltziales), leafy twigs assigned to Elatocladus planus (Pinales) and permineralized trunks and branches ascribed to Cupressinoxylon zamunerae sp. nov. (Pinales), were recognized. The last two species exhibit characters that allow designating them to family Cupressaceae sensu lato. At the same time, it is demonstrated that they belong to the same plant, which is named as the new species of Cupressinoxylon here described. This reconstruction is based on kindred reinforcement and mutual occurrence criteria, besides morphological and anatomical characters. Thus, Cupressinoxylon zamunerae sp. nov. is interpreted as a tree 13 m tall, highly branched, with penultimate order shoots with scale-like leaves and last order shoots with alternate, sessile, single-veined, linear to acicular leaves distributed helically. These records confi rm the presence of Cupressaceae sensu lato since the Triassic in Gondwana.Key words: Barreal-Calingasta, Sorocayense Group, Voltziaceae, Cupressaceae sensu lato.RESUMO -Neste trabalho são descritos lenhos, folhas e ramos para a subclasse Pinidae (Voltziales e Pinales) da Formação Cortaderita (Triássico Médio). Os materiais foram encontrados nas quebradas La Cortaderita e La Tinta, na área de Barreal, bacia de Barreal-Calingasta, precordillera de San Juan, Argentina. Foram reconhecidas folhas correspondentes a três espécies do gênero Heidiphyllum (Voltziales), ramos folhosos atribuídos a Elatocladus planus (Pinales) e lenhos permineralizados designados como Cupressinoxylon zamunerae sp. nov. (Pinales). As duas últimas espécies têm características que permitem atribuí-los para a família Cupressaceae sensu lato. Por isso, neste estudo mostra-se que correspondem a mesma entidade biológica. Assim é descrito com o nome da nova espécie de Cupressinoxylon. Esta reconstrução é baseada em critérios de reforço mútuo e de ocorrência afi ns, além de características morfológicas e anatômicas. Desta forma, Cupressinoxylon zamunerae sp. nov. é interpretada como uma árvore de aproximadamente 13 m de altura, muito ramifi cada, com ramos da penúltima ordem com folhas escamiformes, e ramos de última ordem alternados, com folhas sésseis, uninerveadas, lineares a aciculares distribuídas helicoidalmente. Esses registros confi rmam a presença de Cupressaceae sensu lato, desde o Triássico no Gondwana desde o Triássico. Palavras-chave:Barreal-Calingasta, Grupo Sorocayense, Voltziaceae, Cupressaceae sensu lato.

No abstract