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(American Journal of Botany. 1998;85:1426-1438.)
© 1998 Botanical Society of America, Inc.

Studies in Neotropical paleobotany. XII. A palynoflorafrom the Pliocene Rio Banano Formation of Costa Rica and the Neogenevegetation of Mesoamerica1

Alan Graham2,a and DavidL. Dilchera

a Departmentof Biological Sciences, Kent State University, Kent, Ohio 44242; andFlorida Museum of Natural History, Gainesville, Florida32611


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 LOCALITY, AGE, AND STRATIGRAPHY
 COMPOSITION
 DISCUSSION
 REFERENCES
 
An assemblage of 17 identified and four unknown pollen and sporetypes is reported from the Pliocene Rio Banano Formation of southeasternCosta Rica. The most abundant are monolete fern spores, Palmae, cf.Antrophyum, Symphonia, Pelliceria,Lacmella (previously unreported in the fossil record),Alchornea, and Sabicea. These arrange into twopaleocommunities—mangroves and lowland tropical rain forest. Annual precipitation is estimated at near the present ~3500 mm, butless seasonal, and the MAT (mean annual temperature) at ~27°C. No pollen taxa representing distinctly arid or high-altitude vegetationwas being blown or washed into the coastal depositional basin, and nopollen grains were recovered of northern temperate elements that arepresent in Neogene floras to the north in Guatemala and southeasternMexico. These data are consistent with those from 12 other Miocene andPliocene palynofloras from northern Latin America, indicating the lateappearance of dry habitats and moderate paleoelevations and aprogressive southward introduction of northern temperate elements withlate Cenozoic cooling.

Key Words: CostaRica • palynoflora • Pliocene


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 LOCALITY, AGE, AND STRATIGRAPHY
 COMPOSITION
 DISCUSSION
 REFERENCES
 
The Neogene vegetation and terrestrial paleoenvironments ofMesoamerica are becoming better understood through study of palynoflorasranging in age from early Miocene through middle Pliocene, and extendingfrom Veracruz, Mexico, to the Canal region of central Panama. One ofthese fossil floras is an assemblage of spores and pollen from thePliocene Rio Banano Formation of southeastern Costa Rica. Incombination with 12 other floras of Neogene age and with contextinformation from marine and terrestrial faunas, tectonics, snow-linedepressions, noble gases, oxygen isotope paleotemperature data,sea-level curves, and an array of other approaches, a broad picture isemerging of the biotic and environmental history of the region duringthe Cenozoic.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
LOCALITY, AGE, AND STRATIGRAPHY
 COMPOSITION
 DISCUSSION
 REFERENCES
 
The method used for recovering the plant microfossils from thesediments follows standard techniques described in a number ofpublications (Gray, 1965; Traverse, 1988), and recently outlined forNeogene sediments from Guatemala by Graham (inpress a). Briefly, the sediments were processed through HCl,HF, and HNO3 to remove mineral matter and organic debris,then acetolyzed (nine parts acetic anhydride to one part of concentratedH2SO4), with acetolysis preceded and followed bywashes in glacial acetic acid. The residues were stained with safraninand mounted in Protexx. This mounting medium tends to shrink orpreserve the specimens without swelling (particularly thin-walledtypes), in contrast to glycerine jelly, used in other studies in thisseries, which tends to expand the specimens. Thus, size measurementsfor some of these pollen grains and spores are smaller than forcomparable ones described and illustrated from previously studiedfloras. The specimens were examined and photographed at 400xmagnification with a Leitz Orthoplan Photomicroscope using Panotomic Xblack and white film. Identifications were made by comparisons to aspore and pollen reference collection of ~24 000 slides, andfrom illustrations and descriptions in the literature. Slides,residues, unprocessed samples, negatives, and duplicate prints are inthe palynological collections at Kent State University.


   LOCALITY, AGE, AND STRATIGRAPHY
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 LOCALITY, AGE, AND STRATIGRAPHY
COMPOSITION
 DISCUSSION
 REFERENCES
 
The collection locality is an experimental open pit operated byRECOPE for mining lignite. It is near Zent (10° 02'N,83°17'W), adjacent to the Talamanca Indian Reservation, insoutheastern Costa Rica, ~30 km west southwest of Limón inthe province of Limón. Samples were collected from the hillsideexposure shown in Figs. 1 and2. Maximum thickness of the lignite is ~50 cm, and it isunderlain by a gray organic-rich sandstone and overlain by the weatheredsurface. The samples bearing the most well-preserved and diversepalynomorphs are number 8, ~30.5 cm from the base of the exposure,and especially number 4, ~91 cm from the base. There was nosignificant difference in composition between the two samples, but themost abundant and well-preserved specimens were from sample 4.



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  		Figs. 1–2. Collection locality at RECOPE experimental open pit near Zent, southeastern Costa Rica. 1. Overview of the locality with figures at the collecting horizon. 2. Close-up of the collecting horizon. Photographs by Shirley A. Graham.

 
The Rio Banano Formation was earlier considered to be late Miocene toRecent in age, but mostly Plio-Pleistocene (Taylor, 1975). Escalante (1990, fig. 6) places it in thePlio-Pleistocene and, most recently, Coates etal. (1992) assign it to the middle Pliocene with an agebetween 3.6 and 2.5 Ma.


   COMPOSITION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 LOCALITY, AGE, AND STRATIGRAPHY
 COMPOSITION
DISCUSSION
 REFERENCES
 
Seventeen identified and four unknown spores and pollen types aredescribed from the Rio Banano Formation. In the following descriptionsthe phrase "previous records" refers to other occurrences ofthe taxa in Tertiary palynofloras from northern Latin America. References to these occurrences are provided in Table 1. The sample and slidenumbers are given for each figured specimen, and location of thespecimens on the slides is designated by ESF (England Slide Finder)coordinates. A summary of the composition and numerical representationsis given in Table 2.


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  		Table 1. Approximate age, location, and references to previous rec[chords for Neogene palynofloras of northern Latin America.

 

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  		Table 2. Composition and numerical representation of palynomorphs in sample 4-1, Rio Banano Formation, southeastern Costa Rica. Figures are percentages based on a count of 200 and exclude unknown 2, which numerically constitutes ;mt90% of the assemblage. Dashes indicate presence at <0.5%.

 
Monolete fern spore type 1 (Fig.3; sample 4, slide 2, ESF N-35,1). This is a laevigate tofaintly verrucate spore 54 x 36 µm in size. Type 2 (Fig. 4; sample 4, slide 2, ESF O-41,3;30 x 24 µm) is a smaller version of type 1; type 3 (Fig. 5; sample 4, slide 1, ESF M-51; 60x 39 µm) is verrucate; and type 4 (Fig. 6; sample 4, slide 1, ESF Y-51,3;45 x 33 µm) is coarsely verrucate. These laevigate toverrucate, reniform, monolete fern spores occur in virtually allCenozoic assemblages from northern Latin America. They are similar tothe spores of several genera of the Blechnaceae, Polypodiaceae, andPteridaceae, and serve only to indicate the presence of moisthabitats.



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  		Figs. 3–24. Fossil spores and pollen grains from the Pliocene Rio Banano Formation of southeastern Costa Rica. See text for descriptions and measurements, and Table 2 for numerical representations. 3. Monolete fern spore type 1. 4. Monolete fern spore type 2. 5. Monolete fern spore type 3. 6. Monolete fern spore type 4. 7. Pteris . 8. cf. Antro phyum . 9, 10. Trilete fern spore type 1. 11. Palmae. 12–13. Lacmella . 12. Equatorial view. 13. Surface view. 14. Ilex . 15. Alchornea . 16. Pelliceria . 17. Polygalaceae. 18. Sabicea . 19–20. Symphonia . 19. Equatorial view. 20. Polar view. 21. cf. Psittacanthus . 22. cf. Struthanthus . 23. Unknown 1. 24. Unknown 2.

 
Pteris (Pteridaceae; Fig.7). Triangular, apices rounded; trilete, laesura straight,15–18 µm long, extending to spore margin, inner margin oflaesura lobate, bordered by lip 5–6 µm wide; proximal surfacelaevigate, distal surface coarsely verrucate (? obscure); flange7–9 µm wide bordering outer spore margin, smooth, outer marginentire; wall 2–3 µm thick; size 45 µm. Sample 8, slide 4,ESF W-50,4. Previous records: Artibonite, Cucaracha, Culebra, Gatun,Gatuncillo, Ixtapa, La Boca, Uscari formation/group/sequence.

Pteris is a tree fern typically growing at low tomidelevations in tropical moist and tropical wet forests.

cf. Antrophyum (Vittariaceae; Fig. 8). Oblate to oblate-spheroidal,amb oval-triangular; trilete, laesura straight, narrow, 37–41µm long, extending two-thirds to nearly to spore margin, inner marginentire; laevigate; wall ~2 µm thick; size 67–71 µm. Sample 4, slide 1, ESF P-30,1–3. Previous records: Artibonite,Cucaracha, Culebra, Gatuncillo, Herrería, La Bocaformation/group.

Antrophyum is mostly a pendant, epiphytic fern ofpantropical distribution. In tropical America it grows from Hidalgo,Mexico, to northern Argentina and southeastern Brazil, usually in deepshade in wet to moist forests at elevations of ~100–1500 m(Tryon and Tryon, 1982, p. 360).

Trilete fern spore type 1 (Figs. 9,10). Oblate, amb triangular, apices rounded; trilete, laesurastraight, 8–11 µm long, extending to spore margin, inner marginentire, bordered by faint narrow lip ~2 µm wide; laevigate; wall~2 µm thick; size 24–32 µm. Sample 4, slide 1, ESFH-30,1; Y-44.

This spore cannot be identified to genus, and the general type rangeswidely both stratigraphically and geographically throughout Cenozoicdeposits in northern Latin America.

Palmae (Fig. 11). Prolate,with greatest width just above equator; monocolpate, colpus straight toslightly sinuous, 16–18 µm long, extending entire length ofgrain, inner margin of colpus entire to minutely dentate; finelyreticulate; tectate-perforate, wall homogeneous to columellae justevident (at 400x magnification), ~2 µm thick; size20–22 x 14–16 µm. Sample 4, slide 1, ESFE-48,1–3. Previous record: Gatuncillo Formation.

This generalized type of palm pollen is distinguished by itsrelatively small size, but presently it cannot be identified togenus.

Lacmellea (Apocynaceae; Figs. 12, 13). Oblate, amb circular;tri(col)porate, colpi faint, short (~6 µm equator to apex),apices rounded, frequently obscure and grain appearing triporate, poresconspicuous, equatorially arranged, equidistant, situated at midpoint ofcolpus, circular, 3–4 µm in diameter, inner margin entire tominutely dentate, surrounded by costae pori 2–3 µm wide,surface of costae pori smooth, outer margin slightly diffuse; scabrate;tectate, wall homogeneous to columellae just evident (at 400xmagnification), 2–3 µm thick; size 27–30 µm. Sample4, slide 1, ESF T-49,2–4. Previous record: none.

Lacmella is a genus of 19–20 species of shrubs andtrees to 20 m tall found in tropical regions mostly in South America,but with two species extending into Central America (Nowicke, 1970). The principal Central Americanspecies is L. panamensis distributed from Belizethrough Panama and growing primarily in the lowland tropical wet forest. Lacmella has not been reported previously in the fossilrecord.

Ilex (Aquifoliaceae; Fig.14). Prolate-spheroidal, amb oval to nearly circular;tricolporoidate, colpi equatorially arranged, meridionally elongated,equidistant, straight, 20–22 µm long, inner margin entire, porepoorly defined, frequently obscure, situated at midpoint of colpus;intectate, clavate, wall ~3 µm thick; size 26–28 x19–21 µm. Sample 4, slide 1, ESF W-51,1–2. Previousrecords: Cucaracha, Culebra, Gatun, Ixtapa, La Boca, Gatuncillo, ParajeSolo, San Sebastian formations.

Ilex is a shrub to small tree widespread in tropical Americaand occurs primarily in mesic to slightly drier habitats atmidelevations.

Alchornea (Euphorbiaceae; Fig. 15). Oblate, amb circular;tricolpate, colpi equatorially arranged, meridionally elongated,equidistant, straight, 5–6 µm long, inner margin entire,distinct operculum; psilate; tectate, wall homogeneous (at 400xmagnification), 2 µm thick; size 17–19 µm. Sample 4, slide1, ESF E-30,2. Previous records: Artibonite, Culebra, Cucaracha, Gatun,La Boca, Paraje Solo, San Sebastian, Uscari formation/ group/sequence.

Alchornea is a small deciduous tree widespread in tropicalAmerica. It grows primarily in tropical moist and premontane wetforests at elevations between 300 and 2000 m.

Symphonia (Guttiferae; Figs.19, 20). Oblate, amb polygonal (hexagonal); stephanoporate(pores 6), pores equatorially arranged, equidistant, circular,10–12 µm in diameter, surrounded by irregular, granular costaepori; psilate to scabrate; tectate, wall homogeneous (at 400xmagnification), conspicuously thick (~6 µm); size 43–47µm. Sample 4, slide 1, ESF C-46,1; sample 4, slide 2, ESF C-30. Previous records: Paraje Solo.

Symphonia is a tree to 27 m tall, which is frequentlypollinated by hummingbirds. However, members of the prominent CentralAmerican species S. globulifera often occur in stands,and flower and produce pollen throughout the year, increasing thechances of its representation in the pollen record. Individual treesmay remain in flower for 2 mo. The species is widespread throughtropical America (Belize to South America), and it is a characteristiccomponent of the lowland tropical moist and tropical wet forests. Pollen was recovered in small amounts (<1%) in one sample fromthe Paraje Solo Formation, but in the Rio Banano assemblage it is moreabundant (4%; Table2).

cf. Psittacanthus (Loranthaceae; Fig. 21). Oblate, amb triangular toconcave-triangular, apices rounded to nearly blunt; trisyncolpate, colpiequatorially arranged, meridionally elongated, equidistant, straight,margin entire, 20–22 µm long, extending from pole to apices;scabrate to finely verrucate, scabrae diminishing toward apices,interapical margin dentate in median optical section (scabrae evident),margin of apices entire; tectate, columellae just evident (at 400xmagnification in inter-apical region), wall ~2 µm thick; size33–36 µm. Sample 8, slide 4, ESF Y-42, 3–4. Previousrecord: Gatun (as Loranthaceae type 2; other Loranthaceae types-- ParajeSolo, San Sebastian).

Psittacanthus is a genus of ~80 species of tropicalshrubs. The specimen is most similar to P. schiedanusin our three collections (Arsene 2900, Mexico, US 1001260; no collector,no collection number, Mexico, US 1494987; Schmalzel 1348, Chiriqui,Panama, STRI). However, in Feuer and Kuijt(1979) pollen grains of that species are shown as deeplyconcave and P. sonorae appears more similar.

cf. Struthanthus (Loranthaceae; Fig. 22). Oblate, amb triangular tooval-triangular; tricolpate, colpi equatorially arranged, merdionallyelongated, equidistant, straight, 15–18 µm long, inner marginentire to minutely dentate, syncolpate, colpi apices occasionallybranched and forming triangular area at poles; scabrate; tectate, wallhomogeneous to columellae just evident (at 400x magnification),~2 µm thick; size 29–32 µm. Sample 4, slide 1, ESFX-31,1. Previous record: Paraje Solo.

Struthanthus is a scandent shrub to parasitic vine of40–60 species widely distributed in the American tropics andoccurring in a wide variety of habitats (J. Kuijt, University ofVictoria; personal communication, 1997). For example, S.orbiculatus grows from Mexico to Peru and western Brazil intropical moist, premontane dry, premontane moist, premontane wet,premontane rain, and tropical dry forests. The pollen morphology ofextant species has been described by Feuer andKuijt (1985).

Pelliceria (Pelliceriaceae; Fig. 16). Oblate, amb circular;tricolporate, colpi equatorially arranged, meridionally elongated,equidistant, 20–24 µm long, tapering to acute apex, innermargin entire to minutely dentate, low margo 8–10 µm wide, poreoval to elongated equatorially, 3–4 µm in diameter, situated atmidpoint of colpus, inner margin of pore entire; sculpture variable,scabrate/finely verrucate to coarsely verrucate; tectate, columellaeevident (at 400x magnification), wall 3–4 µm thick; sizevariable, 40–60 µm (figured specimen 60 µm). Sample 4,slide 2, ESF R-43,3. Previous records: Chapelton (Guys Hill Member),Gatuncillo, Ixtapa, La Boca, San Sebastian, Simojovel (La Quinta)groups/formations.

Pelliceria is a small mangrove tree presently distributedfrom coastal Costa Rica to northwest Colombia and Ecuador. During theCenozoic it was widespread in the Gulf/Caribbean region, and it is knownfrom deposits ranging in age from Eocene to Recent and from as far northas Puerto Rico, Jamaica, and southeastern Mexico. The history ofPelliceria and other mangroves in the New World has beensummarized by Graham (1977, 1995).

Polygalaceae (Fig. 17). Prolate to prolate-spheroidal, amb oval; stephanocolporate, colpiequatorially arranged, meridionally elongated, equidistant (~3 µmapart), straight, extending nearly entire length of grain, 20–22µm long, ~5 µm wide, inner margin entire, pores faint,situated at midpoint of colpus, circular, 3–4 µm in diameter;psilate; tectate, wall homogeneous (at 400x magnification), ~2µm thick; size 23–25 µm. Sample 4, slide 1, ESF B-39,4. Previous record: Paraje Solo (pores more distinct).

This pollen type is similar to several types in the Polygalaceae andcannot be referred to genus. Polygala paniculata is awidespread weedy annual herb often growing in clearings, andSecuridaca diversifolia is a shrub or liana growing in tropicaldry to premontane wet forests in Central America.

Sabicea (Rubiaceae; Fig.18). Oblate, amb oval-triangular to nearly circular;tricol(por)pate, colpi equatorially arranged, meridionally elongated,equidistant, inner margin minutely dentate, short (4–6 µm),faint(?) costae colpi, pores faint, equatorially elongated, slit-like(~1 x 3 µm), situated at midpoint of colpus; finelyreticulate, muri smooth, width approximately equal to diameter of lumen(~0.5 µm); tectate-perforate, columellae evident (at 400xmagnification), wall 2–3 µm thick; size 24–26 µm. Sample 4, slide 2, ESF K-36,3–4. Previous record: Culebra (largerspecimen, 32–36 µm).

Sabicea pollen grains from the Culebra Formation also havebeen described and illustrated separately (Graham, 1987a). The pollen is similar among theextant Neotropical species, including the widespread S.villosa (cf. Roubik and Moreno P.,1991, fig. 1081). The genus includes ~125 species ofclimbing shrubs and vines, and in Central America it grows primarily intropical moist and tropical wet forests.

Unknown 1 (Fig. 23). Oblate, amb triangular to oval-triangular; triporate, pores equatoriallyarranged, equidistant, ~3 µm in diameter, inner pore margin± entire, surrounded by faint annulus 3–4 µm wide;verrucate, verrucae irregular, 3–4 µm in diameter, low(1–2 µm); tectate, wall homogeneous (at 400x magnification),~2 µm thick. Size 28–30 µm. Sample 4, slide 2, ESFM-32,4.

Unknown 2 (Fig. 24). Prolate, amb oval; tricolporate, colpi equatorially arranged,meridionally elongated, equidistant, 14–16 µm long, innermargin entire, pores elongated equatorially, oval, ~3 x 5µm, bordered along top and bottom margin by costae pore ~1 µmwide; finely reticulate, muri smooth, approximately equal in width todiameter of lumen (~0.5 µm); tectate-perforate, columellaeevident (at 400x magnification), wall 2–3 µm thick; size26–28 x 25–27 µm. Sample 4, slide 2, ESFB-29,3–4.

Unknown 3 (Figs.25–27). Prolate; tricolporate, colpi equatoriallyarranged, meridionally elongated, equidistant, straight, 17–19µm long, extending nearly entire length of grain, inner margin entireto minutely dentate, narrow costae colpi, pores oval to slit-like,~0.5 x 3–4 µm, situated at midpoint of colpus; finelystriate; tectate, wall homogeneous to columellae just evident (at400x magnification), wall ~2 µm thick; size 25–27x 17–19 µm. Sample 4, slide 1, ESF V-43, Q-50,2–4,F-35,1–2.



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  		Figs. 25–29. Fossil spores and pollen grains from the Pliocene Rio Banano Formation of southeastern Costa Rica. See text for descriptions and measurements, and Table 2 for numerical representations. Figs. 25–27. Unknown 3. 25. Specimen with narrow, slit-like pores. 26. Specimen showing narrow costae colpi. 27. Specimen with more oval pores. Figs. 28, 29. Unknown 4. 28. Polar view. 29. Equatorial view.

 
Although this unknown is only one of 21 types recognized for theflora, it is the prominent pollen type in the Rio Banano assemblage. Inabundance, occurrence in a tropical lowland costal environment,association with Pelliceria, and in size, shape, and generalaperture features it is similar to Rhizophora. However, itlacks the prominent costae colpi, colpi transversalis, and the finelyreticulate sculpture of that genus. The prolate, tricolporate, striatecondition suggests Anacardiaceae (e.g., Tapirira), but in thatfamily the grains are usually larger and the striations are moreprominent. Based on the relatively recent age and modern aspect of theflora, the parent plant is probably a tree or shrub, producing largenumbers of flowers, either abundant or occurring locally in stands (asopposed to isolated individuals), and is likely a prominent member ofthe present lowland tropical vegetation along the Caribbean coast ofCentral America.

Unknown 4 (Figs. 28, 29). Oblate, amb circular; tricolpate, colpi equatorially arranged,meridionally elongated, equidistant, 10–12 µm long, margindiffuse; finely reticulate, muri smooth, width (0.5 µm),approximately one-half diameter of lumen (1 µm); intectate, clavate,wall ~3 µm thick; size 28–30 µm. Sample 4, slide 2, ESFV-39,1–3; sample 4, slide 1, ESF M-51,4.

These specimens are similar to pollen of Tetrorchidium(Euphorbiaceae), which has been reported (as cf. Tetrorchidium)from the Paraje Solo Formation. However, in that genus some of themostly clavate columellae taper to near echinae.

Another pollen type is occasional in the Rio Banano assemblage. Itis a small, thin-walled, finely reticulate form that is probably amonocotyledon. However, the preservation and/or orientation of therelatively few grains made it impossible to determine the nature of theapertures with certainty.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 LOCALITY, AGE, AND STRATIGRAPHY
 COMPOSITION
 DISCUSSION
REFERENCES
 
Paleocommunities and environment
The general paleoenvironmental setting for the Rio Banano assemblageis indicated by the composition of the flora and by the sediment type inwhich the assemblage is preserved. Lignites containing mangroves aredeposited under warm-temperate to tropical, coastal, brackish-waterconditions. Relative sea-level changes, resulting from a combination oftectonics (movement of the land) and eustatic fluctuations (changes insea level independent of land movement), produced periodic inundationsand regressions that account for the cycles of lignite deposition, andexplain the presence of coastal sediments and vegetation at this sitepresently 20 km inland and 100–200 m above the presentcoastline.

Two paleocommunities are evident in the Rio Banano plant microflora. A fringing community of mangroves was present as indicated by pollen ofPelliceria. Immediately inland there was a lowland tropicalrain forest that included Pteris, Palmae, Lacmellea,Alchornea, Symphonia, Psittacanthus,Struthanthus, and Sabicea. In the Rio Banano florathere are no taxa suggesting upland habitats (e.g., Pinus,Podocarpus, Alfaroa/Oreomunnea,Quercus), and there is no evidence for dry to arid vegetationin the immediate vicinity of the depositional basin, althoughIlex and Struthanthus can range into these habitats. Also, there is no pollen of northern temperate elements as found in thePliocene Paraje Solo and Padre Miguel floras to the north.

The paleovegetation of the Rio Banano Formation is similar to the(potential) extant vegetation of lowland tropical southeastern CostaRica and, therefore, the present climate gives an approximation of thepaleoclimate. The mean annual precipitation at Limón is~3500 mm and seasonal, with the drier part of the year occurringbetween January and March, although there is no pronounced dry season. The MAT (mean annual temperature) is ~27 C (Portig, 1976). At this value, temperature wouldnot be a limiting factor for mangrove-tropical rain forest vegetation,so the paleobotanically derived approximation is a minimum for thecoastal terrestrial habitats in the region. For the interval between3.6 and 2.5 Ma (million years ago), mean SST (sea-surface temperature)for the Colombia Basin to the south is estimated at warmer than thepresent 27.9C based on ostracode evidence (Coates et al., 1992).

The Neogene palynofloras of northern LatinAmerica
The Rio Banano palynoflora is one of 13 Neogene assemblages known forthe region between southern Mexico and central Panama (Table 1; Fig. 30). Each of these floras revealsthe paleovegetation and environments within a limited area, butcollectively they reveal something of the biotic diversity, climate andclimatic change, the biotic responses to these changes, sea-levelfluctuations, landscape evolution, lineage histories, and migrations. The Rio Banano flora is the latest Neogene plant microfossil assemblageto be included in the project, Studies in Neotropical Paleobotany, andthe results are incorporated into a summary of the Miocene throughPliocene palynofloras reported from northern Latin America (Table 3).



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  		Fig. 30. Index map of palynofloras mentioned in the text. See Table 1 for age and references. 1 = Paraje Solo, 2 = Ixtapa, 3 = La Quinta (Simojovel), 4 = Padre Miguel, 5 = Herrería, 6 = Rio Banano, 7 = Culebra, Cucaracha, La Boca, Gatun, 8 = Uscari, 9 = Artibonite.

 

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  		Table 3. Summary of Neogene palynofloras from northern Latin America. 1 = Paraje Solo, 2 = Herrer;aaia, 3 = Rio Banano, 4 = Artibonite, 5 = Gatun, 6 = Padre Miguel, 7 = Ixtapa, 8 = Cucaracha, 9 = Culebra, 10 = La Boca, 11 = Uscari, 12 = La Quinta (Simojovel). Specimens not cited as to biological affinities (e.g., Liliacidites ) and identifications above the level of family (e.g., monolete fern spores) are not included. See Table 1 for age, localities, and references for the floras.

 
In the Rio Banano flora and in the Cucaracha, Culebra, Gatun, and LaBoca floras, the tropical rain forest is well represented. This is incontrast to several other Neogene floras in northern Latin America wherethe rain forest is poorly represented or absent. The Paraje Solo floraof southeastern Veracruz, Mexico is also preserved in coastal lignitesand associated sediments. It was deposited in the middle Pliocene(Planktic Foraminiferal Zone 19, 3–4 Ma) during a periodconsidered by Cronin and Dowsett (1991)to represent the maximum of Pliocene warmth. Yet the flora providesclear evidence of cool climates (presence of Picea, lowering ofecotones, distruption of the rain forest). If the period of warmth wasas substantial and widespread as suggested by Cronin and Dowsett (1991), then an alternativeexplanation must be offered for the cool conditions suggested by theParaje Solo flora. The likely explanation is upwelling of cool to coldbottom waters that often results along coastal areas with increasedrates of ocean circulation. In the Gulf/Caribbean region this increasedrate was due to the closing of the Isthmus of Panama that intensifedflow of the Gulf Stream between ~3.5 and 2.5 Ma (Coates et al., 1992; Graham, 1992; Jackson,Budd, and Coates, 1996; Webb and Rancy,1996; Burnham and Graham, inpress). In the Pliocene Herrería flora of coastalsoutheastern Guatemala (Graham, in pressa), mangroves were present (Acrostichum,Rhizophora) but the surrounding vegetation was mostly afern-sedge-palm marsh or swamp. The more inland Padre Miguel flora ofGuatemala is a sedge marsh with grasses and composites, and pine-oak,temperate (Alfaroa-Oreomunnea, Juglans,Ulmus), and possibly cool-temperate (Picea,Pinus, Quercus) forests in the uplands. In theHerrería, Padre Miguel, and Paraje Solo floras the lowlandtropical rain forest is absent or poorly represented, but for differentreasons. In the Herrería flora high water tables produced swampsand marshes that were priodically innundated by marine waters. ThePadre Miguel flora was deposited inland and adjacent to more uplandhabitats where Picea, Pinus,Alfaroa-Oreomunnea, Juglans,Quercus, and Ulmus were contributing the prominentpalynomorphs. In the Paraje Solo flora it was likely a combination ofhigher mid-Pliocene sea levels that reduced available lowland habitatsbetween the coast and the adjacent mountains, and locally cool climatesresulting, in part, from upwelling.

Areas of significant physiographic relief existed in the vicinity ofthe Paraje Solo flora, moderate elevations are suggested by the PadreMiguel flora, and only low elevations are indicated by the Cucaracha,Culebra, Herrería, La Boca, Uscari, and Rio Banano floras (to~1400 m). By Gatun time, elevations in central Panama increased to~1700 m, initiating a differentiation into wet Atlantic and drierPacific sides, the appearance of slightly drier vegetation (viz.Gramineae, Acacia, Allophylus, Bursera,Cedrela, Ceiba, Combretum, cf.Jatropha, Posoqueria, Pseudobombax,Serjania), and uplands sufficient to support restrictedtemperate plants (viz. the first appearance of Quercus insouthern Central America). However, in none of these Neogene floras isthere any evidence for extensive, well-developed dry-habitat vegetationthat would suggest an arid corridor connecting the North and SouthAmerican continents. Disjuncts between the arid regions of North andSouth America (e.g., Larrea; Hunzikeret al., 1972; Orians and Solbrig,1977; Thrower and Bradbury,1977; Kalin Arroyo, Zedler, and Fox,1995) likely orignated, at least in large part, vialong-distance transport (Raven, 1963,1971, 1973; Raven and Axelrod,1975; Graham, in press b[chapter 9]).

The Rio Banano assemblage contains no spore or pollen taxa ofnorthern temperate elements, and this is consistent with the patternemerging from the study of other floras. Pollen of Pinus,Alnus, Betula, Carya, Castanea,Celtis, Fagus, Quercus, Nyssa,Juglans, Ostrya-Carpinus,Platanus, Tilia, and Ulmus are present inPaleogene deposits in southeastern United States (Gray, 1960; Frederiksen, 1981, 1988, 1991), but none have been found inPaleogene floras from Mexico through Central America. There are few(Picea, Pinus?) in the early Miocene La Quinta(Simojovel) flora, and none in the early Miocene Cucaracha, Culebra, LaBoca, or Uscari floras of Panama and Costa Rica. With the exception ofPinus, none were reported from the middle Miocene Ixtapa flora. A surprising mixture of pollen and spore types from plants ofpresent-day temperate and tropical regions of eastern and western NorthAmerica, eastern Asia, tropical southeastern Asia, and tropical Africahas been reported for Chiapas, Mexico in various abstracts, unpublishedtheses, and dissertations (Davalia, Nypa,Cedrus, Cupressus, Keteleeria,Pseudotsuga, Sequoia, Tsuga,Baikiaea, Nothofagus, Platycarya). Descriptions and illustrations are not provided, or are inadequate toassess the identifications, and the reports are not included here. Theearliest accepted appearance of relatively extensive northern temperateelements in the northern Latin American biota is in the Paraje Soloflora (Abies, Picea, Pinus, Alnus,Celtis, Juglans, Liquidambar,Myrica, Populus, Quercus, Ulmus) andin the Padre Miguel flora (Picea, Pinus,Juglans, Quercus, Ulmus). Quercus(only) is recovered in small quantities in the Gatun flora, andAlnus and Quercus first appear in northern SouthAmerica in the Quaternary (Hooghiemstra,1989, 1994; Hooghiemstra and Sarmiento, 1991; Hooghiemstra and Ran, 1994). Theserecords suggest a generally progressive southward migration coincidingwith a significant drop in global benthic MAT in the middle Miocene, andcontinuing into later times as revealed by oxygen isotope data (Miller, Fairbanks, and Mountain, 1987).

These 13 Neogene floras, distributed from southeastern Mexico throughcentral Panama and the Antilles, constitute the meager plant microfossildatabase for reconstructing vegetation, lineages, environments, andmigrations through the region for the Miocene through the Pliocene. Some trends are evident, however, and collectively the assemblages arebegining to reveal the complex mosaic of vegetation that characterizednorthern Latin America during the Cenozoic and the various factors ofclimate, upwelling, topography, tectonics, and sea-level changes thatinfluenced itsdevelopment.


   FOOTNOTES
 
1 The authors (AG) thank Ricardo Granados and G. A. Lezana F. (Instituto Costaricense Electricidad), Luis Obando (Escuela Centroamericana de Geología), and Rogelio Samuels (RECOPE) for information on the localities and for field assistance in collections made during 1981, 1983, and 1992. Luis D. Gomez P. provided valuable cooperation throughout the study. DLD thanks Eduardo Libby (Universidad de Costa Rica), Ferrnado Alvarado Villalón (RECOPE) for information and field assistance during 1991. Research supported by NSF grants DEB-8007312 and DEB-9206743 (AG).


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   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 LOCALITY, AGE, AND STRATIGRAPHY
 COMPOSITION
 DISCUSSION
 REFERENCES
 
Burnham, R. J., and A. Graham. Inpress. The history of neotropical vegetation: new developments andstatus. Annals of the Missouri Botanical Garden.

Coates, A. G., J. B. C. Jackson, L. S.Collins, T. M. Cronin, H. J. Dowsett, L. M. Bybell, P. Jung, andJ. A. Obando. 1992 Closure of the Isthmus of Panama:the near-shore marine record of Costa Rica and western Panama. Geological Society of America Bulletin 104:814–828.[Abstract/Free Full Text]

Cronin, T. M., and H. J. Dowsett [guesteds.]. 1991 Pliocene climates. QuaternaryScience Reviews 10: 1–296.

Escalante, G. 1990 Thegeology of southern Central America and western Colombia. InG. Dengo and J. E. Case [eds.], The Caribbean region,201–230. Geological Society of America, Boulder, CO.

Feuer, S., and J.Kuijt. 1979 Pollen morphology and evolution inPsittacanthus (Loranthaceae). Botanical Notiser132:295–309.

———, and———. 1985 Fine structure of mistletoepollen VI. Small-flowered neotropical Loranthaceae. Annals of theMissouri Botanical Garden 72: 187–212. [CrossRef][ISI]

Frederiksen, N.O. 1981 Middle Eocene to early Oligocene plantcommunities of the Gulf Coast. In J. Gray, A. J. Boucot, andW. B. Berry [eds.], Communities of the past, 493–549.Dowden, Hutchinson and Ross, Stroudsburg, PA.

———. 1988 Sporomorphbiostratigraphy, floral changes, and paleoclimatology, Eocene andearliest Oligocene of the eastern Gulf Coast. United StatesGeological Survey Professional Paper 1448: 1–68.

———. 1991 Pulses ofmiddle Eocene to earliest Oligocene climatic deterioration in southernCalifornia and the Gulf Coast. Palaios 6:564–571.[Abstract/Free Full Text]

Graham, A. 1976 Studies inneotropical paleobotany. II. The Miocene communities of Veracruz,Mexico. Annals of the Missouri Botanical Garden 63:787–842.[CrossRef][ISI]

———. 1977 Newrecords of Pelliceria (Theaceae/Pelliceriaceae) in theTertiary of the Caribbean. Biotropica 9:48–52.[CrossRef][ISI]

———. 1985 Studies inneotropical paleobotany. IV. The Eocene communities of Panama. Annals of the the Missouri Botanical Garden 72:504–534.

———. 1987a Fossilpollen of Sabicea (Rubiaceae) from the lower Miocene CulebraFormation of Panama. Annals of the Missouri Botanical Garden74: 868–870. [CrossRef][ISI]

———. 1987b Miocenecommunities and paleoenvironments of southern Costa Rica. AmericanJournal of Botany 74: 1501–1518. [CrossRef][ISI]

———. 1988a Studiesin neotropical paleobotany. V. The lower Miocene communities of Panama--the Culebra Formation. Annals of the Missouri Botanical Garden75: 1440–1466. [CrossRef][ISI]

———. 1988b Studiesin neotropical paleobotany. VI. The lower Miocene communities ofPanama-- the Cucaracha Formation. Annals of the Missouri BotanicalGarden 75: 1467–1479. [CrossRef][ISI]

———. 1989 Studies inneotropical paleobotany. VII. The lower Miocene communities of Panama--the La Boca Formation. Annals of the Missouri Botanical Garden76: 50–66. [CrossRef][ISI]

———. 1990 LateTertiary microfossil flora from the Republic of Haiti. AmericanJournal of Botany 77: 911–926. [CrossRef][ISI]

———. 1991a Studiesin neotropical paleobotany. VIII. The Pliocene communities of Panama--introduction and ferns, gymnosperms, angiosperms (monocots). Annalsof the Missouri Botanical Garden 78: 190–200. [CrossRef][ISI]

———. 1991b Studiesin neotropical paleobotany. IX. The Pliocene communities of Panama--angiosperms (dicots). Annals of the Missouri Botanical Garden78: 201–223. [CrossRef][ISI]

———. 1991c Studiesin neotropical paleobotany. X. The Pliocene communities of Panama--composition, numerical representations, and paleocommunitypaleoenvironmental reconstructions. Annals of the MissouriBotanical Garden 78: 465–475. [CrossRef][ISI]

———. 1992 Utilization of theisthmian land bridge during the Cenozoic—paleobotanical evidencefor timing, and the selective influence of altitudes and climate. Review of Palaeobotany and Palynology 72:119–128.[CrossRef]

———. 1993a Historical factorsand biological diversity in Mexico. In T. P. Ramamoorthy, R.Bye, A. Lot, and J. Fa [eds.], Biological diversity of Mexico,109–127. Oxford University Press, New York, NY.

———. 1993b Contributiontoward a Tertiary palynostratigraphy for Jamaica: the status of Tertiarypaleobotanical studies in northern Latin America and preliminaryanalysis of the Guys Hill Member (Chapelton Formation, middle Eocene) of Jamaica. In R. M. Wright and E. Robinson [eds.], Biostratigraphy of Jamaica, 443–461. Geological Society of America Memoir 182. Geological Society of America, Boulder,CO.

———. 1995 Diversification ofGulf/Caribbean mangrove communities through Cenozoic time. Biotropica 27: 20–27. [CrossRef][ISI]

———. In pressa Studies in neotropical paleobotany. XI. Late Tertiary vegetationand environments of southeastern Guatemala: palynofloras from theMio-Pliocene Padre Miguel Group and the Pliocene HerreríaFormation. American Journal of Botany.

———. In pressb Late Cretaceous and Cenozoic history of North Americanvegetation (north of Mexico). Oxford University Press,Oxford.

———. In pressc Studies in Neotropical paleobotany. XIII. An Oligo-Miocenepalynoflora from Simojovel (Chiapas, Mexico). American Journal ofBotany.

———, and D. M.Jarzen. 1969 Studies in neotropical paleobotany. I. TheOligocene communities of Puerto Rico. Annals of the MissouriBotanical Garden 56: 308–357.

———, and R. PalaciosChávez. 1996 Additions and preliminary study ofan Oligo-Miocene palynoflora from Chiapas, Mexico. Rheedea 6:1–12.

Gray, J. 1960 Temperatepollen genera in the Eocene (Claiborne) flora, Alabama. Science 132: 808–110. [Abstract/Free Full Text]

———(Coordinator). 1965 Techniques in palynology. In B. Kummel and D. Raup [eds.], Handbook ofpaleontological techniques, 471–706. W. H. Freeman, SanFrancisco, CA.

Hooghiemstra,H. 1989 Quaternary and upper Pliocene glaciations andforest development in the tropical Andes: evidence from a longhigh-resolution pollen record from the sedimentary basin ofBogotá. Palaeogeography, Palaeoclimatology,Palaeoecology 72: 11–26.

———. 1994 Pliocene-Quaternaryfloral migration, evolution of northern Andean ecosystems and climaticchange: implications from the closure of the Panamanian Isthmus. Profile 7: 413–425.

———, and E. T. H.Ran. 1994 Late and middle Pleistocene climatic changeand forest development in Colombia: pollen record Funza II (1–158m core interval). Palaeogeography, Palaeoclimatology,Palaeoecology 109: 211–246. [CrossRef]

———, and G.Sarmiento. 1991 New long continental pollen recordfrom a tropical intermontane basin: late Pliocene and Pleistocenehistory from a 540 m-core. Episodes 14:107–115.

Hunziker, J. H., R. A. Palacios, A. G. deValesi, and L. Poggio. 1972 Species disjunctions inLarrea: evidence from morphology, cytogenetics, phenoliccompounds, and seed albumins. Annals of the Missouri BotanicalGarden 59: 224–233. [CrossRef][ISI]

Jackson, J. B. C., A. F. Budd, and A. G.Coates [eds.]. 1996 Evolution and environmentin tropical America. University of Chicago Press, Chicago,IL.

Kalin Arroyo, M. T., P. H. Zedler, and M. D.Fox [eds.]. 1995 Ecology and biogeography ofMediterranean ecosystems in Chile, California, and Australia. Ecological Studies, vol. 108. Springer-Verlag, Berlin.

Langenheim, J. H., B. L. Hackner, and A.Bartlett. 1967 Mangrove pollen at the depositional siteof Oligo-Miocene amber from Chiapas, Mexico. Botanical MuseumLeaflets Harvard University 21: 289–324.

Martínez-Hernández,E. 1992 Caracterizacion ambiental del Terciario de laregion de Ixtapa, estado de Chiapas-- un enfoquepalinoestratigráfico. Universidad Nacional Autonoma deMexico, Instituto de Geologia, Revista 10:54–64.

Miller, K. G., R. G. Fairbanks, and G. S.Mountain. 1987 Tertiary oxygen isotope synthesis, sealevel history, and continental margin erosion. Paleoceanography 2: 1–19.

Nowicke, J.W. 1970 Apocynaceae. In R. E. Woodson, Jr.,R. W. Schery, and Collaborators, Flora of Panama, 59–130. Annals of the Missouri Botanical Garden 57.

Orians, G. H., and O. T. Solbrig[eds.]. 1977 Convergent evolutionin warm deserts. Dowden, Hutchinson and Ross, Stroudsburg,PA.

Palacios Chávez, R., and J.Rzedowski. 1993 Estudio palinologico de las florasfosiles del Miocene inferior y principios del Mioceno medio de laregion de Pichucalco, Chiapas, Mexico. Acta BotánicaMexicana 24: 1–96.

Portig, W. H. 1976 Theclimate of Central America. In W. Schwerdtfeger[ed.], Climates of Central and South America, 405–478. World Survey of Climatology, vol. 12. Elsevier, Amsterdam.

Raven, P.H. 1963 Amphitropical relationships in the floras of North and South America. Quarterly Review of Biology 38:151–177.[CrossRef][ISI]

———. 1971 Therelationships between 'Mediterranean' floras. In P.H. Davis, P. C. Harper, and I. C. Hedge [eds.], Plant life ofsouth-west Asia, 119–134. Botanical Society of Edinburgh,Edinburgh.

———. 1973 Theevolution of mediterranean floras. In F. di Castri and H. A.Mooney [eds.], Mediterranean type ecosystems, origin andstructure, 213–224. Ecological Studies, vol. 7. Springer-Verlag, Berlin.

———, and D. I.Axelrod. 1975 History of the flora and fauna of LatinAmerrica. American Scientist 63: 420–429.

Roubik, D. W., and J. E. MorenoP. 1991 Pollen and spores of Barro Colorado Island. Monographs in Systematic Botany 36.

Taylor, G. D. 1975, Thegeology of the Limón area of Costa Rica. Ph.D. dissertation,Louisiana State University, Baton Rough, LA.

Thrower, N. J. W., and D. E. Bradbury[eds.]. 1977 Chile-California Mediterraneanscrub atlas, a comparative analysis. Dowden, Hutchinson and Ross,Stroudsburg, PA.

Traverse,A. 1988 Paleopalynology. Unwin Hyman, Boston,MA.

Tryon, R. M., and A. F.Tryon. 1982 Ferns and allied plants. Springer-Verlag,Berlin.

Webb, S. D., and A.Rancy. 1996 Late Cenozoic evolution of the neotropicalmammal fauna. In J. B. C. Jackson, A. F. Budd, and A. G.Coates [eds.], Evolution and environment in tropical America,335–358. University of Chicago Press, Chicago,IL.




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