6 - The Cenozoic record of tropical dry forest in northern Latin America and the southern United States  pp. 124-145

The Cenozoic record of tropical dry forest in northern Latin America and the southern United States

By Alan Graham and David Dilcher

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The history of a plant community is reconstructed from remains preserved in a fragmentary fossil record. The completeness of the reconstructed community is, in part, a function of whether the community grew under conditions favorable to the preservation of macro- and microfossils. Macrofossil assemblages (leaves, fruits, seeds, wood) generally record plants growing near the site of deposition, and these afford opportunities to determine the general vegetation type and the paleoclimate by comparisons with modern analogs and by the use of leaf physiognomy. Microfossils (pollen, spores, trichomes, cuticles, phytoliths, microscopic organisms) provide a record of the regional vegetation, and also include species often not represented by macrofossils, such as annual, suffrutescent and herbaceous plants. Each methodology has its own set of strengths, weaknesses, practitioners and advocates, but the most complete history of plant communities is produced when both macro- and microfossil floras are available.

Northern Latin America

In the case of the tropical dry forest in northern Latin America, the reconstruction of its history is made more challenging by the facts that (1) dry environments have fewer sites of deposition, and less water for the transport of remains to these sites, and (2) there are very few well-preserved Tertiary macrofossil floras of significant size or diversity known for northern Latin America. An exception is the Oligocene San Sebastian flora from Puerto Rico, but it has not been studied or revised since Hollick's (1928) original publication.