Abstract Detail

Paleobotanical Section

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

First megafossil records of several plant taxa from the Pliocene Citronelle Formation of Alabama.

The current reinvestigation of the Pliocene (Piacenzian) Citronelle Formation from sites in southern Alabama is bringing to light first geological macrofossil records of extant plant taxa that still occupy the area today. We have already described first records of Betula nigra and Carpinus caroliniana based upon fruit and leaf evidence. In 1916, Berry described the fossil species Nyssa aquaticaformis from the Citronelle Formation based upon the typical stony fruits of Nyssa and described the presence of extant Planera aquatica based upon leaves only. We document the presence of large, obovate, entire-margined leaves with long petioles consistent with modern Nyssa aquatica, allowing us to produce a combination fruit and leaf record for the modern species. We also substantiate the presence of Planera aquatica with a record of a typical fruit surrounded by irregular projections. While Berry noted Vitis fruit from the Citronelle Formation, we have compression/impression fossils of the characteristic cordiform, dentate leaves of Vitis rotundifolia. The distinctive leaf characteristics of Populus deltoides (truncated base, dentate, round sinuses between teeth) and Liquidambar styraciflua (deeply-lobed five-part leaves that give the species a star-like appearance) as shown in Citronelle Formation fossils are the basis for documenting the existence of these taxa in the Pliocene as well. We will show Pliocene evidence exists for the small, dry drupes of Cyrilla racemiflora with their persistent calyces and styles. Additionally, the Citronelle Formation is providing a North American Pliocene macrofossil record for many taxa that, previously, have not been reliably documented from the Pliocene. We present a leaf and fruit record of Cocculus (partial leaf with wide base and lobes; semi-circular seed with wrinkled ridges), a record of Cornus stones, and a probable record of Gordonia based upon distinctive leaf characteristics (partial leaf with appressed, uniformly-spaced crenations).

Broader Impacts:
This research provides many first records of several important plant taxa of the Eastern Deciduous Forest, which is important in biogeographical, phylogenetic and paleoclimatic reconstructions.

1 - University of South Alabama, Department of Marine Sciences, Life Sciences Bldg 25, Mobile, Alabama, 36688, USA
2 - University of South Alabama, Biological Sciences, Life Sciences Building 124, Mobile, AL, 36688, United States

Keywords:
Pliocene
Citronelle Formation
First records.

Presentation Type: Oral Paper:Papers for Sections
Session: 58
Location: 556A/Convention Center
Date: Wednesday, August 4th, 2010
Time: 2:00 PM
Number: 58003
Abstract ID:267