Wilf, Peter , Little, Stefan A. , Iglesias, Ari , Zamaloa, Maria , Gandolfo, Maria , Johnson, Kirk , Cuneo, Nestor .
Discovery of Papuacedrus (Cupressaceae, Libocedrinae) in Eocene Patagonia Clarifies the Southern Rainforest Enigma.
The early Eocene Laguna del Hunco (LH) and middle Eocene RÃo PichileufÃº (RP) compression floras from Patagonia, Argentina are diverse, angiosperm-dominated assemblages from lowland, caldera-lake environments. They contain lineages now found in the tropical West Pacific, the Neotropics, and the Andean-Patagonian temperate rainforests. Leaf size data from recent collections indicate annual precipitation > 1 m, and Gymnostoma (LH) and drought-intolerant Podocarpaceae genera (LH, RP) support high rainfall. However, “Libocedrus” prechilensis Berry 1938 is apparently affiliated with dry biomes: the name reflects similarity to an extant Patagonian endemic, Austrocedrus (then Libocedrus) chilensis, which inhabits cold steppe to northern Mediterranean climates. The holotype (RP), a vegetative branch, was the sole South American fossil reliably assigned to Libocedrinae Farjon, comprised of Austrocedrus, Libocedrus (New Zealand, New Caledonia), Papuacedrus (New Guinea and Moluccas), and Pilgerodendron (Southern Andes). New specimens referable to “L.” prechilensis (30 LH, 3 RP) preserve diagnostic characters not of Austrocedrus, but of Papuacedrus, including: large (to 10 mm length, juvenile type) lateral leaves in fused pairs, with convex bases, sharp-pointed, spreading free tips, darkened margins, and conspicuous resin ducts; smaller (to 0.3 mm), keeled facial leaves with comblike marginal flanges; and Florin rings in discontinuous rows. An attached seed cone (3.5 x 2.8 mm) has two decussate, unequally-sized pairs of cone scales, with a bract tip preserved near the center of an upper cone scale from which surface rugosities radiate both basally and apically. The previous fossil record of Papuacedrus is based on leaves with cuticle from the Oligocene-Miocene of Tasmania and the Miocene of New Zealand. The sole extant species, P. papuana, is most prevalent in New Guinea cloud forests receiving up to 4 m rainfall annually. Thus, our pending new combination removes a dry-biome indicator for Eocene Patagonia and adds a link to tropical, West Pacific, montane rainforest.
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1 - Pennsylvania State University, Department of Geosciences, University Park, PA, 16802, USA
2 - Universidad de Buenos Aires, Depto. Ecología, Genética y Evolución, Int. Güiraldes 2620, Buenos Aires, Buenos Aires, C1428EHA, Argentina
3 - Cornell University, LH Bailey Hortorium, 462 Mann Library, Ithaca, New York, 14853-4301, USA
4 - Denver Museum of Nature & Science, Department of Earth Sciences, Denver, CO, 80205, USA
5 - Museo Paleontológico Egidio Feruglio-CONICET, Av. Fontana 140, Trelew, Chubut, CP9100, Argentina
Laguna del Hunco
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 2:30 PM