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Cone scales and leaves of the Araucariaceae are reported from the Loreto Formation in Río de Las Minas, Punta Arenas, Chile. Two types of cone scales including one new species, Araucarites alatisquamosus are recognized. They are similar to Araucaria section Eutacta. Two types of leaves are assigned to Araucaria nathorstii Dusén, and one new type is distinguished in the specimens from the type locality of A. nathorstii. A narrow leaf type is identical to Dusén's 'Blätter der sterilen Zweige (leaves of sterile shoot)' of A. nathorstii, and a broad leaf type is identical to his 'Blätter der fertilen Zweige (leaves of fertile shoot)'. Both types show characters of leaves of section Araucaria as suggested by earlier studies. A smaller leaf type differs from the original description of A. nathorstii, and consists of small appressed leaves with the obtuse apex and stomatal orientation that are the characteristic of the section Eutacta. The occurrence of leaves and cone scales similar to section Eutacta suggest the presence of araucarians close to this section in southernmost South America during the Eocene-early Oligocene, and provide evidence for the wide distribution and diversity of genus Araucaria relatives in South America during the Paleogene. [ABSTRACT FROM AUTHOR]

The cycads pose classic problems in evolutionary biogeography, owing to their far-flung extant distributions and the sparse fossil records of living genera. A noteworthy example is Tribe Encephalarteae of Family Zamiaceae, today consisting of Encephalartos (Africa) and the Australian genera Lepidozamia and Macrozamia. Numerous petrified trunks of Encephalarteae described from the Cretaceous of Patagonia, Antarctica, and India indicate far larger past distributions across Gondwana and subsequent extinctions. The only fossils close to the current range are Paleogene leaf fragments from Australia assigned to Lepidozamia and Macrozamia. Here, we report a large frond piece and several isolated leaflets of a compressed cycad, along with an associated spiny petiole, from the late-Gondwanan, 52.2 Ma Laguna del Hunco flora of Patagonia, Argentina. Austrozamia stockeyi gen. et sp. nov., has the novel combination of an Encephalartos-type leaf and Lepidozamia-type cuticle. The Australian Lepidozamia fossils, widely used for molecular clock calibrations, could also represent an extinct genus. Austrozamia stockeyi demonstrates survival of the Encephalarteae in Patagonia and presumably across Gondwana until its terminal phase, adding a striking new component to the growing list of South American plant extinctions associated with Antarctic separation and related climate changes. [ABSTRACT FROM AUTHOR]

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Copyright of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Variations in the architecture and axis structure of different growth forms of Nothofagus pumilio (Poepp. et Endl.) Krasser (Nothofagaceae) were studied along an altitudinal gradient. We evaluated the primary growth and branching pattern of annual shoots belonging to the main axis categories (trunk, main branches, and secondary (short) branches) of four growth forms developed at different altitudes (1200–1600 m a.s.l.) in northern Patagonia: (i) low shrubs at the high-altitude timberline, (ii) high shrubs at high altitude, (iii) low trees at mid-altitude slopes, and (iv) high trees at low-altitude single-species forests. Shoot structure and branch distribution along shoots were similar for all axis categories and growth forms. Significant differences between axis categories were found regarding the sizes of shoots, which decreased from trunk to secondary/short branches. For each axis category, shoots of similar size differed between growth forms in stem slenderness and internode length. The extent of differentiation between axis categories is key in the structural distinction between growth forms of N. pumilio. [ABSTRACT FROM AUTHOR]