Hudson, Patrick J. , Boucher, Lisa .
An aquatic angiosperm from the Late Cretaceous of New Mexico.
Compressions of a reduced aquatic angiosperm, which include vegetative and reproductive structures, are described from Late Cretaceous (late Campanian-early Maastrichtian) exposures of the Fruitland-Kirtland Formation in the San Juan Basin, northwestern New Mexico. Approximately 50 specimens, about 16 with fertile structures, are in a fine clay matrix. The sedimentology and associated remains of "Pistia" and Nelumbo-like leaves support the hypothesis that this plant inhabited low energy environments, such as shallow ponds. The plant has separate vegetative and reproductive shoots that are produced along a common stem. Structures interpreted as leaves, or leaflets, are attached sub-oppositely along the vegetative shoot and are overlapping on branches that range up to approximately 16 mm in length, with the largest fragment having 30 sets. Basal sets average approximately 1.6 mm in length and 0.84 mm in width, and both dimensions decrease gradually towards the apex. Each leaf or leaflet has two to four primary veins with reticulate venation between them. Stalks bearing clusters of elliptical reproductive structures are attached basally relative to the vegetative shoot. These structures are an average of 0.26 x 0.45 mm in diameter. Thin-walled monosulcate pollen grains, measuring approximately 30 x 35 µm in diameter, were isolated from these structures. Based on overall morphology, venation pattern of the leaves/leaflets, characters of the pollen grains and depositional environment, the specimens are identified as the remains of an aquatic monocot possibly belonging to the Alismatales.
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1 - University of Nebraska Omaha, Department of Biology, 6001 Dodge Street, Omaha, Nebraska, 68182-0040, USA
Presentation Type: Oral Paper
Location: Salon G - Austin Grand Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 9:00 AM