A Complete Herbaceous Fossil of Pontederites hesperida: New Insights Into the Morphology of an Extinct Aquatic Plant

Session: 37th Annual Undergraduate Research Exhibition Sponsored by Sigma Gamma Epsilon (Posters)

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Abstract:

     The newly recovered specimen, was found in the Lower Eocene age Gastropod Beds of Fossil Lake in the Green River Group, Southwest Wyoming.  It has been identified as Pontederites hesperida based on leaf shape and venation. The slightly younger holotype of Pontederites hesperida (Knowlton) in collections at the Smithsonian was the only known specimen of its genus and species.  This genus was based on a fragmentary leaf from the Parachute Creek Member of the Lake Uinta deposits of the Green River Group 40 miles west of Meeker, Colorado. The new specimen is the complete herbaceous structure as it would have grown in life.  The preservation of such a complete herbaceous plant informs us about the paleo environment of Fossil Lake at the time, and confirms with confidence the identification of both fossils to the aquatic family Pontederiaceae.  When compared to modern species of Pontederiaceae this fossil displays remarkably little evolutionary change. The discovery and identification of this fossil displays the importance of continued excavation in Fossil Lake as many non fish species found are known only from a single specimen and new species are found every year.