Abstract Detail



Paleobotany

Stults, Debra [1], Axsmith, Brian [2].

Preliminary analysis reveals a diversity of Quercus fruit/cupule morphotypes from two Late Miocene localities in eastern North America.

Numerous Quercus fruits specimens, mostly represented by cupules, from two sites in eastern North America (the Brandywine site in Maryland, ~ 10 to 6 Ma, and the Mauvilla site in south Alabama, 7.3 to 6.8 Ma) have been recovered. Specimens are mostly small, but of significant maturity to distinguish important characters. Characters emphasized in this analysis include overall shape and depth of the cupule, appressed or loose cupule scales, degree of cupule rim uniformity, uniformity in size and shape of the cupule scales, presence or absence of thickenings on the scales, overall scale outline (e.g., triangular, lanceolate), pubescence, and blunt vs. acute scale apices. A useful feature more conspicuous on the fossils than living specimens, probably due to taphonomic effects, is a darkened rim on the scale margins, which represents a smooth edge on modern specimens. Several morphotypes are recognized from the Brandywine, and several others occur at Mauvilla. Although, some of the Mauvilla fruits contain nutlets, they have not been used in this study and will be described in forthcoming analyses. So far, only cupules have been found from the Brandywine flora. Most North American Quercus fossil records are based on leaves and pollen. Quercus fossil fruits are not as common, especially from eastern North American sites, which is remarkable considering that the genus is such an important component of the modern North American Eastern Deciduous Forest Biome. Furthermore, fruit production is often high, and the nutlets and cupules should have high fossilization potential. The previous Quercus fruit record from eastern North America and the Gulf Coastal Plain consists only of a single fruit from the Oligocene Catahoula Formation in east Texas, one probable Early Miocene specimen from the Brandon Lignite of Vermont, and several undescribed, small and/or charcoalified specimens from the Mio-Pliocene Gray Fossil site of eastern Tennessee. The original description of the Brandywine flora included mention of three types of Quercus leaves, but only one type of fruit. The morphotypes from these two fossil sites are mostly distinctive, suggesting climatic or depositional dissimilarities between these localities during the Miocene. This ongoing research indicates that several different Quercus species occurred on the mid-Atlantic and Gulf of Mexico Coastal Plains during the latter Miocene, which is important since this region is now a significant locus of Quercus diversity and abundance.


1 - 27640 Rigsby Road, Daphne, AL, 36526, United States
2 - Biology Department, 5871 USA Drive North, Room 124, Mobile, AL, 36688, United States

Keywords:
Brandywine Formation
Mauvilla Site
Miocene
Quercus
cupule.

Presentation Type: Oral Paper
Number:
Abstract ID:337
Candidate for Awards:None


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