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  • 1.
    CARPENTER, RAYMOND
    et al.
    University of Tasmania.
    McLoughlin, Stephen
    Swedish Museum of Natural History, Department of Paleobiology.
    HILL, ROBERT
    University of Adelaide.
    McNAMARA, KENNETH
    University of Cambridge.
    JORDAN, GREGORY
    University of Tasmania.
    EARLY EVIDENCE OF XEROMORPHY IN ANGIOSPERMS: STOMATAL ENCRYPTION IN A NEW EOCENE SPECIES OF BANKSIA (PROTEACEAE) FROM WESTERN AUSTRALIA2014In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 101, no 9, p. 1486-1497Article in journal (Refereed)
    Abstract [en]

    Premise of the study: Globally, the origins of xeromorphic traits in modern angiosperm lineages are obscure but are thought to be linked to the early Neogene onset of seasonally arid climates. Stomatal encryption is a xeromorphic trait that is prominent in Banksia , an archetypal genus centered in one of the world’s most diverse ecosystems, the ancient infertile landscape of Mediterranean-climate southwestern Australia.

    Methods: We describe Banksia paleocrypta , a sclerophyllous species with encrypted stomata from silcretes of the Walebing and Kojonup regions of southwestern Australia dated as Late Eocene.

    Key results: Banksia paleocrypta shows evidence of foliar xeromorphy ~20 Ma before the widely accepted timing for the onset of aridity in Australia. Species of Banksia subgenus Banksia with very similar leaves are extant in southwestern Australia. The conditions required for silcrete formation infer fl uctuating water tables and climatic seasonality in southwestern Australia in the Eocene, and seasonality is supported by the paucity of angiosperm closed-forest elements among the fossil taxa preserved with B. paleocrypta. However, climates in the region during the Eocene are unlikely to have experienced seasons as hot and dry as present-day summers.

    Conclusions: The presence of B. paleocrypta within the center of diversity of subgenus Banksia in edaphically ancient southwestern Australia is consistent with the continuous presence of this lineage in the region for ≥ 40 Ma, a testament to the success of increasingly xeromorphic traits in Banksia over an interval in which numerous other lineages became extinct.

  • 2.
    Friis, Else Marie
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Crane, Peter Robert
    Oak Spring Garden Foundation, Virginia, USA.
    Pedersen, Kaj Raunsgaard
    Århus University, Denmark.
    Tanispermum, a new genus of distinctive hemi-orthotropous to hemi-anatropous angiosperm seeds from the Early Cretaceous of eastern North America2018In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 105, p. 1369-1388Article in journal (Refereed)
    Abstract [en]

    PREMISE OF THE STUDY:

    Exotestal seeds with characters that indicate relationship to extant Austrobaileyales and Nymphaeales are abundant in Early Cretaceous sediments from Portugal and eastern North America, but their variety and unique features provide evidence of extensive extinct diversity among early angiosperms.

    METHODS:

    The fossils were extracted from Early Cretaceous sediments from Virginia and Maryland, United States, by sieving in water. After cleaning with HF, HCl and water, they were examined using SEM and SRXTM and compared to seeds of extant and fossil angiosperms.

    KEY RESULTS:

    A new genus, Tanispermum gen. nov., with four species (T. hopewellense sp. nov., T. marylandense sp. nov., T. drewriense sp. nov., and T. antiquum sp. nov.) is recognized. Relationship with extant Austrobaileyales and Nymphaeales is indicated by an exotesta of tall palisade sclerenchyma with undulate anticlinal walls forming a jigsaw puzzle-like surface pattern. However, seeds of Tanispermum differ from those of Austrobaileyales and Nymphaeales in their hemi-orthotropous-hemi-anatropous organization. Attempts to place Tanispermum in a phylogenetic context confront a variety of problems, including lack of information on other parts of these extinct plants.

    CONCLUSIONS:

    The discovery highlights the extent to which the morphology of extant angiosperms is not representative of the diversity that once existed among early-diverging members of the group. The relictual nature of extant taxa near the base of the angiosperm tree greatly complicates the reconstruction of ancestral character states and emphasizes the need for focused paleobotanical studies to elucidate the extinct diversity that existed early in angiosperm evolution.

  • 3.
    McLoughlin, Stephen
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Carpenter, Raymond J
    Jordan, Gregory J
    Hill, Robert S
    Seed ferns survived the end-Cretaceous mass extinction in Tasmania.2008In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 95, no 4, p. 465-71Article in journal (Refereed)
    Abstract [en]

    Seed ferns, dominant elements of the vegetation in many parts of the world from the Triassic to Cretaceous, were considered to have disappeared at the end of the Cretaceous together with several other groups that had occupied key positions in terrestrial and marine ecosystems such as dinosaurs, plesiosaurs, and ammonoids. Seed-fern demise is generally correlated with competition from diversifying flowering plants through the Cretaceous and the global environmental crisis related to the Chicxulub impact event in the paleotropics at the end of the period. New fossils from Tasmania show that one seed-fern lineage survived into the Cenozoic by at least 13 million years. These fossils are described here as a new species, Komlopteris cenozoicus. Komlopteris is a genus of seed ferns attributed to Corystospermaceae and until now was not known from sediments younger than the Early Cretaceous. Discovery of this "Lazarus taxon," together with the presence of a range of other relictual fossil and extant organisms in Tasmania, other southern Gondwanan provinces, and some regions of northern North America and Asia, underscores high-latitude regions as biodiversity refugia during global environmental crises and highlights their importance as sources of postextinction radiations.

  • 4.
    Razafimandimbison, Sylvain
    et al.
    Swedish Museum of Natural History, Department of Botany.
    Kainulainen, Kent
    Niklas, Wikström
    Bremer, Birgitta
    Historical biogeography and phylogeny of the pantropical Psychotrieae alliance (Rubiaceae), with particular emphasis on the Western Indian Ocean Region2017In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 104, p. 1407-1423Article in journal (Refereed)
    Abstract [en]

    PREMISE OF THE STUDY: The Western Indian Ocean Region (WIOR) is a biodiversity hotspot providing an ideal setting for exploring the origins of insular biodiversity and dynamics of island colonization. We aimed to investigate the origins of the WIOR Psychotrieae alliance (Rubiaceae) with typically small, probably mainly bird-dispersed drupes, and the timing and direction or sequence of its colonization events in the region.

    METHODS: We used the program BEAST to estimate divergence times and Lagrange for biogeographic reconstruction.

    KEY RESULTS: The alliance has reached the WIOR at least 14 times via dispersals from Africa along with Asia and the Pacifi c mostly during the last 10 My, with at least one back-colonization to Africa. We inferred the earliest dispersal to Madagascar from the Pacifi c or Asia in the Miocene and numerous out-of-Madagascar dispersals to the nearby archipelagos but no dispersal out of those archipelagos. Gynochthodes with multiple fruits reached Madagascar twice from the Pacifi c possibly via ocean drifting. Psychotria with dry fruits (schizocarps) colonized Madagascar from the Pacific or Asia before reaching the Comoros from Madagascar possibly via wind dispersal.

    CONCLUSIONS: This study reinforces the pivotal role of dispersal in shaping the WIOR biodiversity and as the critical initiating step in the generation of endemic biodiversity on its islands. The WIOR alliance shows strong Asian and Pacifi c affi nities despite the proximity of the region to Africa. Madagascar has served as a stepping-stone for subsequent dispersal to the rest of the region. The Afro-Malagasy-Seychelles genus Craterispermum and the Malagasy Puffia may represent relictual lineages.

  • 5. Sadowski, Eva-Maria
    Denk, Thomas (Contributor)
    Synchrotron X- ray imaging of a dichasium cupule of Castanopsis from Eocene Baltic amber2018In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 105, no 12, p. 1-12Article in journal (Refereed)
  • 6.
    Sadowski, Eva-Maria
    et al.
    Department of Geobiology, University of Göttingen Goldschmidtstraße 3, 37077 Göttingen, Germany.
    Hammel, Jörg U.
    Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht, Germany.
    Denk, Thomas
    Swedish Museum of Natural History, Department of Paleobiology.
    Synchrotron X-rayimaging of a dichasium cupule of Castanopsis from Eocene Baltic amber2018In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 105, p. 2015-2036Article in journal (Refereed)
    Abstract [en]

    The partial female inflorescence reported here provides an important addition to acorns of Castanopsis described from middle Eocene strata of Europe. Furthermore, the intercontinental distribution of Castanopsis in the Eocene is confirmed. The amber fossil also broadens the picture of the Baltic amber source area, indicating oligotrophic, sandy, bog-like habitats. Finally, this study underscores the great benefit of SRμCT as a powerful tool to investigate plant inclusions from amber in a nondestructive way.

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