Studies in Neotropical Paleobotany. I. The Oligocene Communities of Puerto Rico
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Abstract
Studies are being made of plant microfossils from seven Tertiary formations in Mexico Panama, and Puerto Rico.The Puerto Rican samples from the Oligocene San bon Formation have yielded 165 morphological forms; 44 have been identified, and 15 P these have no previously known fossil record.Community types include a coastal, brackish-water the three temperate trees require habitats not presently available on the island.The temperate element suggests altitudes greater than those of today, and recently available geological data reveal the presence of Oligocene highlands of 13,000 to 15,000 feet elevation.These would x ran to provide cool-temperate conditions in an insular environment at 18 degrees Ancestral pea Rico (Hispaniola, Puerto Rico, and the Virgin Islands) provided an fective landbridge between northern South America, the West Indies, and Mexico (Yucawever, the O Oligocene seas extended across at least part of peninsula Florida and us to 120 miles inland along the Texas Gulf Coast; thus the barrier to migration from the Antilles into southeastern North America was probably greater than at present.Of the 44 genera identified all have affinities with northern South America, eastern Mexico, and the Antilles; and none have exclusive affinities with the vegetation of southeastem North America.Studies from Panama and Veracruz, Mexico, suggest tropical puri in. the modern and fossil yis of southeastern North America were introduced along an Isthmian-coastal Mexico route during the early Tertiary or subsequently through long-To dispersal into tropical par pes page peninsula Florida).The tropics are generally recognized as an important center for biological diversity, and a number of studies are underway dealing with the systematics, ecology, and evolutionary aspects of tropical plant communities.The more recent