Dunn, Michael T .
A new isoetalean fossil plant reconstructed from permineralized and compression fossils from the Mississippian (Serpukhovian) Pride Mountain Formation of northern Alabama.
A fossil assemblage from the Pride Mountain Formation (Mississippian/Serpukhovian) has recently been recovered from the Tuscumbia Limestone Quarry in northern Alabama. Plant remains co-occur with marine invertebrates and include a single type of rooting base preserved as casts and permineralized specimens, a single stem type preserved as compressions and permineralizations, a single type of leaf, and sporophylls preserved as compressions. These factors suggest that this assemblage represents a monospecific salt marsh and facilitates the reconstruction of the whole-plant. These plants are semi-herbaceous with frequent branching ranging from equal to unequal-dichotomous to pseudomonopodial. The lobed base produces forking rootlets and a limited amount of secondary xylem. The protostele is surrounded by numerous mesarch to exarch protoxylem poles at the apices of short, acute lobes. Phloem is not observed, but is represented by a lacuna encircling the stele. The cortex is three-zoned with a thin inner cortex consisting of usually poorly preserved thick walled cells, a middle cortex of thin walled cells, and an outer zone of thick walled cells. A periderm is observed at the margin of the outer cortex in the cormose bases and the proximal portions of some stems. External to the periderm, several morphologies of decortication tissues are preserved on the exterior of compression and permineralized stems. Helically produced leaf traces pass through the cortex at a steep angle and vascularize ligulate leaves with truncate bases and acute tips. Sporophylls are produced along the stems among the vegetative leaves. Trilete megaspores are ornamented by spines, and are of the Triletes type. Microspores are not yet known.
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1 - Cameron University, Department of Biological Sciences, Science Complex, Lawton, Oklahoma, 73505, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 555B/Convention Center
Date: Monday, August 2nd, 2010
Time: 2:30 PM