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Although too young to provide a calibration point for molecular divergence-time estimates, this fossil is noteworthy as the first macrofossil record of Begonia. It may represent a species that initially arrived from the south via Mexico after the closing of the Central American Straits. We propose that this fossil should stimulate a reexamination of other unidentified fossil winged fruits, as older records of Begonia may be forthcoming.

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The late Pliocene was an important time of relatively recent global warmth, and it heralded the end of Neogene Epoch. However, plant fossils from this time are uncommon in North America. This study provides detailed descriptions of 23 plant fossil taxa representing 14 woody angiosperm families from the late Pliocene (mid-Piacenzian) Citronelle Formation in coastal Alabama. This is the only significant late Pliocene megafossil plant assemblage in eastern North America, and one of the few from the entire Neogene of this region. Many are first records of their kind, and several are confidently identified to the species level. Overall, the floral composition is similar to that of the modern Gulf Coast. These findings, along with previous records, form the basis of quantitative paleoclimate estimates using leaf margin analysis (LMA), the Coexistence Approach (CoA), the Bioclimatic Analysis/Mutual Climate Range Technique (BA/ MCRT), and the climate leaf multivariate program (CLAMP). The CLAMP analysis had the highest site-to-site disparity and provided anomalously low mean annual temperature (MAT) and mean annual precipitation (MAP) values. The LMA, CoA analysis, and BA/MCRT results are likely better proxies in this case, as the climate estimates obtained are closer to independent proxies and modern values. The BA/MCRT MAT results were most convincing at 18ºC. Nevertheless, higher MAT results were expected, as the mid-Piacenzian was a time of global warmth. Precipitation estimates below modern values obtained in all the relevant analyses are consistent with the presence of white pine in the Citronelle flora.

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Carpinus is a common and widespread element of the modern North American forest vegetation, but its scant fossil record on the continent is perplexing, especially considering the abundant and relatively continuous record of the genus in the Tertiary of Europe and Asia. Despite earlier claims of Tertiary Carpinus remains, recent reviews have indicated that a definitive post-Eocene Tertiary record of the genus in North America is lacking. Therefore, it remains uncertain if Carpinus was present but left no clear fossil record or if the genus became extinct in North America and migrated back to the continent more recently. A reinvestigation of the Citronelle Formation paleoflora has yielded conclusive evidence for the presence of Carpinus in the Gulf Coastal Plain of Alabama during the Pliocene based upon the discovery of a nutlet bract. Carpinus bracts are distinctive and consist of a central bract fused basally with two lateral bractlets. This specimen provides proof of the existence of Carpinus on this continent by the Pliocene Epoch, and any future research on the biogeography of the genus must consider this as the earliest, post-Eocene record of the genus in North America based on unequivocal reproductive structures.