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June 2005

Volume 165, Number 6
Am Nat 2005. Vol. 165, pp. 634–650
0003-0147/2005/16506-40660$15.00
DOI: 10.1086/430055

Eocene Plant Diversity at Laguna del Hunco and Río Pichileufú, Patagonia, Argentina

Peter Wilf,1,*

Kirk R. Johnson,2,

N. Rubén Cúneo,3,

M. Elliot Smith,4,§

Bradley S. Singer,4, and

Maria A. Gandolfo5,#

1. Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802;

2. Department of Earth Sciences, Denver Museum of Nature and Science, Denver, Colorado 80205;

3. Museo Paleontológico Egidio Feruglio, Trelew, Chubut 9100, Argentina;

4. Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706;

5. L. H. Bailey Hortorium, Department of Plant Biology, Cornell University, Ithaca, New York 14853

Abstract:

The origins of South America’s exceptional plant diversity are poorly known from the fossil record. We report on unbiased quantitative collections of fossil floras from Laguna del Hunco (LH) and Río Pichileufú (RP) in Patagonia, Argentina. These sites represent a frost‐free humid biome in South American middle latitudes of the globally warm Eocene. At LH, from 4,303 identified specimens, we recognize 186 species of plant organs and 152 species of leaves. Adjusted for sample size, the LH flora is more diverse than comparable Eocene floras known from other continents. The RP flora shares several taxa with LH and appears to be as rich, although sampling is preliminary. The two floras were previously considered coeval. However, 40Ar/39Ar dating of three ash‐fall tuff beds in close stratigraphic association with the RP flora indicates an age of Ma, 4.5 million years younger than LH, for which one tuff is reanalyzed here as Ma. Thus, diverse floral associations in Patagonia evolved by the Eocene, possibly in response to global warming, and were persistent and areally extensive. This suggests extraordinary richness at low latitudes via the latitudinal diversity gradient, corroborated by published palynological data from the Eocene of Colombia.

Submitted October 1, 2004; Accepted February 9, 2005; Electronically published April 7, 2005

Keywords:

biodiversity, Eocene, geochronology, paleobotany, paleoclimate, Patagonia.

Editor: Jonathan B. Losos

Associate Editor: Mark Westoby

Cited by

LAURA C. SARZETTI, CONRAD C. LABANDEIRA, JORGE F. GENISE. (2008) A LEAFCUTTER BEE TRACE FOSSIL FROM THE MIDDLE EOCENE OF PATAGONIA, ARGENTINA, AND A REVIEW OF MEGACHILID (HYMENOPTERA) ICHNOLOGY. Palaeontology 51:4, 933-941
Online publication date: 1-Aug-2008.
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P. Wilf. (2008) Insect-damaged fossil leaves record food web response to ancient climate change and extinction. New Phytologist 178:3, 486-502
Online publication date: 1-Jun-2008.
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Marcelo A. Aizen, Cecilia Ezcurra. (2008) Do leaf margins of the temperate forest flora of southern South America reflect a warmer past?. Global Ecology and Biogeography 17:2, 164-174
Online publication date: 1-Apr-2008.
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Daniel J. Peppe, Leo J. Hickey, Ian M. Miller, Walton A. Green. (2008) A Morphotype Catalogue, Floristic Analysis and Stratigraphic Description of the Aspen Shale Flora(Cretaceous–Albian) of Southwestern Wyoming. Bulletin of the Peabody Museum of Natural History 49:2, 181
Online publication date: 1-Feb-2008.
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Surangi W. Punyasena, Gidon Eshel, Jennifer C. McElwain. (2007) The influence of climate on the spatial patterning of Neotropical plant families. Journal of Biogeography 0:0, 070901070439001-???
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Ari Iglesias, Peter Wilf, Kirk R. Johnson, Alba B. Zamuner, N. Rubén Cúneo, Sergio D. Matheos, Bradley S. Singer. (2007) A Paleocene lowland macroflora from Patagonia reveals significantly greater richness than North American analogs. Geology 35:10, 947
Online publication date: 1-Feb-2007.
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Online publication date: 1-Nov-2006.
Bradford A. Hawkins, Jose Alexandre Felizola Diniz-Filho, Carlos A. Jaramillo, Stephen A. Soeller. (2006) Post-Eocene climate change, niche conservatism, and the latitudinal diversity gradient of New World birds. Journal of Biogeography 33:5, 770-780
Online publication date: 1-Jun-2006.
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S. Bruce Archibald, Stefan P. Cover, Corrie S. Moreau. (2006) Bulldog Ants of the Eocene Okanagan Highlands and History of the Subfamily (Hymenoptera: Formicidae: Myrmeciinae). Annals of the Entomological Society of America 99:3, 487
Online publication date: 1-Feb-2006.
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