Iglesias, Ari , Wilf, Peter , Gandolfo, Maria , Little, Stefan A. , Johnson, Kirk , Zamuner, Alba B. , Labandeira, Conrad C. , Cuneo, Nestor .
Paleocene Patagonian floras: in situ cuticles complement architectural data from leaf compressions of Podocarpaceae, Lauraceae, and Nothofagaceae.
To test and refine identifications based previously on leaf architectural characters, we are investigating cuticle remains found in situ on compressed leaves from four lower and middle Paleocene taphofloras from Patagonia, Argentina. This approach allows us to better estimate species diversity from morphotypes that could not be split using macroscopic architecture alone. Selected, abundant leaf morphotypes with well preserved cuticle were studied with epifluorescence, transmitted light, and scanning electron microscopy. Comparisons to extant and fossil cuticles validated assignments to the families Podocarpaceae, Lauraceae, and Nothofagaceae. Cuticle of a morphotype architecturally similar to Akania, did not match extant Akania cuticles. A broad-and subopposite-leaved conifer with multiple parallel venation and no midvein (“Zamia” tertiaria Engelhardt 1891), has cuticle characters diagnostic of Podocarpaceae, allowing us to reject architecturally identical Agathis. The “Z.” tertiaria morphotype ranges from the Maastrichtian through the middle Eocene in Patagonia. Lauraceae cuticles are recognized from stomatal characters (guard cells embedded in the subsidiary cells) and presence of simple hairs. Variation in cuticle features allows more species to be recognized than predicted from leaf architecture alone, showing that Lauraceae was a diversified group during the Paleocene in Patagonia. Nothofagus is recognized based on consistent leaf architecture and cuticular features of Berry’s 1937 “Dryophyllum” australis. This is the oldest cuticle and macrofossil record of the genus for South America, corroborating poorly dated pollen records and providing a well-calibrated biogeographic datum for this important Southern group. The recognition of broad-leaved Podocarpaceae, large Nothofagus leaves, and diverse and dominant Lauraceae supports a humid, frost-free biome for these Patagonian paleofloras, as indicated by leaf margin and leaf area analyses and other proxies.
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1 - Pennsylvania State University, Department of Geosciences, University Park, PA, 16802, USA
2 - Cornell University, LH Bailey Hortorium, Dept. Plant Biology, 228 Plant Science Building, Ithaca, New York, 14853, USA
3 - Denver Museum of Natural History and Earth Science, Denver, Colorado, 80205, USA
4 - Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Pla, Departamento Paleobotanica, Paseo del Bosque s/n, La Plata, Buenos Aires, 1900, Argentina
5 - Smithsonian Institution, Department of Paleobiology, Washington, DC, 20013, USA
6 - Museo Paleontológico Egidio Feruglio-CONICET, Av. Fontana 140, Trelew, Chubut, CP9100, Argentina
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 1:45 PM